A new PCB version is available: version 6 batch 1 Check out the schematics, and assembly instructions. What is new in this version? There is no modifications on the functionalities of the board. However, the previous version of the PCB had a bill of material relying on different suppliers, and with parts that were not […]
For the low-voltage testing of the board, you need a dummy microcontroller.
There are two ways of assembling the dummy microcontroller:
Using a prototyping board
Make a circuit based on the schematics below:
The side with the arrow goes towards the top of the SHVPS board.
Using a PCB
The files to make the PCB are in the download section. It is included as a project in the Altium file of the HVPS PCB (file LV_tester.PrjPCB), or available in Gerber format. The components you need are listed in the Bill of Material file (BOM-SHVPS.xlsx) available in the download section in the tab “Low-voltage-tester”. It simply consists in a switch, a 220 Ohm resistor, a LED, and 2x 17-pin headers. The two white lines (on the side opposite the switch) represents the USB connector of the real arduino micro and must match the white lines printed on the SHVPS board (i.e. the top of the board).
The information in how to build a stand-alone High-voltage power supply is now available on the website. The stand-alone configuration combines a single-channel HVPS, a Raspberry Pi, a LCD touchscreen, and a battery. This enables to have a stand-alone unit that does not rely on an external computer and power source. This is for example […]
The battery charging circuit is required to provide battery power for running the standalone configuration of PetapicoVoltron (PPV) that includes a HVPS power supply, a Raspberry Pi and a touchscreen in order to make a completely stand-alone unit. Its functions are
- Manage the charging/discharging of the battery used to power the circuit
- Step up the battery voltage to power the different components (HVPS, Raspberry Pi, and touchscreen)
- Manage communication from an external computer, so that the stand-alone configuration can also be controlled from an external computer.
The different parts of the circuit are described below.
The battery charger IC (U2) is a switch mode charger (BQ24192 by Texas Instruments) which bucks down the supply voltage to charge the battery at high efficiency. This charger works with single cell Li-Po or Li-Ion batteries, which have a typical voltage range of 2.6-4.2 V. In the design presented here, the default maximum charging current is 3A, which is set by the value of R15. However, the charger will adapt to the current capabilities of the charging source. The battery can be charge using two different ports: 1) the DC Jack (P5) which can safely tolerate voltages in the range 5-15 V and can be used to charge the battery at high current. 2) the micro USB plug (P3). By default the USB current draw is limited to 500mA. P13 and P14 are two headers for LEDs that give information on the status of the charger. STAT (P13) will turn on while charging and blink there is a problem (no battery,no thermistor, etc.) !PG (P14) is used to show that a charging source is available. In other word, if the circuit is connected to a source of power that can be used to charge the battery, P14 will be on. P13 turns off once the battery is charged.
P7 and P8 are two connections for 10 kΩ NTC thermistors that enable sensing the temperature of the battery and prevent damage. Using two sensors enables monitoring the battery temperature at two different location. If a single sensor is used, the second must be replaced by a fixed 10 kΩ resistor, or the circuit won’t work (STAT LED will blink). The circuit is protected against short circuit of the battery, and if more than 9A is drawn from the battery, the battery will be disconnected. All charging source must be removed to reset the charger.
The Boost Converter (U3) steps up the protected battery voltage VSYS to a 5 V supply rail to power the different components: Raspberry Pi, LCD screen, and HVPS. P9 is a header for a switch which enables to connect the battery to the converter. This switch can therefore be used as a main power switch. This circuit uses the on resistance of the MOSFET (Q2) as a current sense resistance. This improves efficiency by limits the adaptability of the system. In the current configuration, this puts a limit on the current drawn from the 5V rail to 3.9 – 4.8 A, depending on the temperature and battery charge state. Higher currents will cause a voltage drop of the 5V supply rail. The 5 V rail is fed to three different locations. Header P2 (see complete schematics on the top of the page) powers the Raspberry Pi. Header P10 powers the LCD touch screen, and header P11 powers the HVPS.
USB to serial converter
The micro USB connector on the board has two functionalities
- It enables charging the battery through the USB connector (providing jumper H2 is set)
- It enables sending commands to the HVPS. In the stand-alone configuration, the HVPS USB port is connected to the Raspberry Pi. However, the USB connector of the battery management circuit is connected to a USB-to-Serial chip, which also lowers the communication voltage to 3.3 V, to make it compatible to the Raspberry Pi. The serial output of the chip is connected to the Raspberry Pi, thus enabling communication with the Pi from an external computer. The Python HVPS user interface has a serial listening mode, which forwards any instruction received by the Pi to the HVPS. Therefore, in stand-alone configuration, direct control of the HVPS from an external computer remains possible
Peta-pico-Voltron is an easy-to-build, affordable power supply. One of its limitations is that it requires a computer to run the user interface, and an external power supply. The Python interface can run on a multitude of platforms and allows to mitigate the first issue by allowing to run the interface on tablets, but the requirement for a power supply still remains.
Here we present a completely standalone version of the Peta-pico-voltron power supply, which includes a rechargeable Li-po battery, and a touchscreen.
The bill of materials for the stand-alone configuration is available on the download page. One sheet of the excel file describes the component required for the battery management circuit, and the other sheet describes the other components required (battery, Raspberry Pi, touchscreen, etc.)
Required components and preparation
High Voltage power supply
- You need a fully functional single channel high voltage power supply. Follow the instructions on this web site to assemble, configure, and calibrate a single channel HVPS.
- In the assembly procedure, be sure to solder the 2-pin headers hD3 and hS2, as the main switch and the HV on LED will be panel mounted.
- Once your HVPS is assembled and calibrated, connect it to a computer (see Direct communication with the HVPS) and enter the command SPowJack 0 to tell the HVPS that the external power doesn’t come from the DC jack J1.
- On the HVPS PCB, move the jumper h5V from the on to the off position. The HVPS won’t be powered by the DC jack, but directly by the 5V line on the 10-pin header.
Raspberry Pi and LCD touch screen
- You will need a Raspberry Pi (Raspberry Pi 3 Model B, 16GB Micro SD Card with NOOBS Pre-loaded)
- You will also need the 7” LCD touchscreen (Raspberry Pi 7″ Touch Screen Display with 10 Finger Capacitive Touch)
- Connect the Raspberry Pi to a monitor (this doesn’t need to be the LCD touchscreen at this stage. You can use the HDMI connector of the Pi to connect to any monitor).
- Install the python graphic user interface. In preparation of the use of the interface on the touch screen, and because the interface uses the entire screen, it is recommended to auto-hide the taskbar of the Raspberry Pi. To auto-hide the task-bar, right-click on it and select ‘‘Panel Settings”. Click on the ‘‘Advanced” tab, and check ‘‘Minimize panel when not in use”.
- If you intend to use the USB port of the battery management circuit to send commands to the HVPS (to be able to control the HVPS with an external computer), follow the instructions described in the file install.txt located in the Python interface folder.
- Connect the HVPS to one of the Raspberry Pi USB ports, and check that the interface and the HVPS are communicating.
Pre-assembly of touch screen and Raspberry Pi
- On the LCD touchscreen control board, install the flat cable on the right and install a power cable on the 5pin GPIO connector of the controller. You can solder the cable directly to the GPIO GND and 5V pins. At the other end, install the connector P10 mate (Digikey WM2014-ND, 5 Position Rectangular Housing Connector Receptacle White)
- Install the Raspberry Pi on top of the touchscreen control circuit, as illustrated in the figure below. Use the M2.5 screws included with the screen to secure the Pi, except on the top left corner, where you should use the M2.5 30mm spacer (Digikey AE10789-ND, HEX STANDOFF M2.5 BRASS 30MM). Connect the display cable to the Raspberry Pi
Battery Management circuit
The Battery management circuit functionalities are described on the battery management PCB page.
The sheet Battery Management PCB of the stand-alone configuration BOM lists all the components required to assemble the battery management PCB, and the Altium/Gerber PCB files are available in the download section. The silk overlay on the PCB gives all the indication required on the location of each component, and assembling the board should therefore be straightforward.
- Solder the components of the bill of materials of the battery management PCB (sheet Battery management PCB) on the board. The names of the components are clearly labelled on the PCB silkscreen and correspond to the name given in the bill of material (column Designator).
- Prepare the LEDs (2 (recommend red and green) for the battery management circuit, 1 for the HVPS high voltage on indicator), Switches (1 for power, 1 for high voltage enable on the HVPS), thermistors, and battery with wires and the appropriate connector (see bill of materials). The figure below illustrates the different connectors on the battery management PCB (but P7, P8, P13, and P14) have been replaced by 2-pin headers).
Housing for the stand-alone configuration
You will find a zip archive in the download page, enclosure section with a Solidworks model of an enclosure for the stand-alone configuration. There is a Laser_cutting subfolder with SVG files ready to be cut with a laser cutter. Each part should be cut in a 3 mm plastic sheet (e.g. PMMA), except for HVPS_support.svg that needs to be cut in a 6mm plate. This part also requires the addition of two M2 tapped holes on the side, as shown on the Solidwork file of this part (enclosure/HVPS_support.SLDPRT) that are used to hold the HVPS PCB. Double-sided adhesive can also be used instead, if you want to avoid adding the two M2 holes. The file complete_assembly.SLDASM shows how all parts fit together. Glue is required to assemble the different parts. Use a glue compatible with the plastic you are using.
Pre-assembly of the enclosure
- Cut all parts of the file screen_holder.svg in a 3mm-thick plastic plate, such as PMMA. The text indications included on the part can either be etched on the surface, or should be written with a pen, as they help placing the parts for which orientation matter.
- In the above file, the 4 identical parts are used to hold together the top and bottom plates to the sides. The two 2.5 mm holes in each part must be threaded with a M3 tap.
- Cut the part HVPS_support.svg in a 6mm-thick plastic plate. This part also requires the addition of two M2 tapped holes on the side, as shown on the Solidwork file of this part (enclosure/HVPS_support.SLDPRT) that are used to hold the HVPS PCB. Double-sided adhesive can also be used instead, if you want to avoid adding the two M2 holes.
- Assemble all of the parts you have prepared according to the image below. Pay attention to the orientation of the different parts. You should be able to clear any ambiguity by referring to the picture. (Note the two M2 screws that have been added to indicate the location of the two M2 holes on the part HVPS_support). Use glue to hold the parts together. You will have two parts left that will be used for the bottom of the box.
- Cut the parts side_1.svg, side_2.svg, side_3.svg, and side_4.svg and assemble them as shown on the image below. The text added to the SVG file indicate which side of the parts goes in the inside of the enclosure. In addition, the text should be oriented in the same direction on the four different parts.
- Cut the part bottom.svg and assemble the two parts that remain from the screen holder in the holes on the side
- Install the two switches and the 3 LEDs on the side of the enclosure. Use a bit of glue to hold the LEDs.
- Use double-sided tape to attach the battery (AliExpress 32612003056, 3.7 V 10000 mah tablet battery brand tablet gm lithium polymer battery) to the bottom plate. Fix the two thermistors with tape at different location on the battery. It is also recommended to add an insulation layer on top of the battery, such as a thin PET sheet, or some polyimide tape to protect is from the high voltage of the HVPS PCB.
Assembly of the stand-alone unit
- Insert the LCD screen with the Pi in the screen holder. On the left, use two M3 screws to secure the screen to the holder to the screen. On the right place the Management PCB first on top of the screen holder, and use two M3 screws to hold together the PCB, the screen holder and the screen (see picture, but note that the wires on the top of the battery management PCB have been replaced by headers)
- Use a flat cable (20 lines) to connect connector P2 on the batter management PCB to pins 1 to 20 of the Raspberry Pi GPIO port. Ifyou use a 20-pin connector on the Raspberry Pi side, you will need to cut pins 21 and 22 of the GPIO port. You can also use a 40-pin connector and clamp the 20-wire cable on pins 1–20. The power connector of the screen is connected to P10 on the battery management PCB.
- Install the HVPS PCB on top, fixing it on the 30 mm post with a M2.5 screw, and on the HVPS_holder part on the left with 2 M2 screws, or with adhesive if you haven’t made holes for the screws.
- Prepare a cable to power the HVPS with 2 5-pin connectors (Digikey WM2014-ND, 5 Position Rectangular Housing Connector Receptacle White). 5 V is on pin 2, and GND on pin 4. One end connects to connector P11 of the battery management PCB, and the other end to pins 1-5 of the 10-pin header of the HVPS.
- Use the right angle USB cable (Aliexpress 32753222490, Right Angle Micro USB Data Cable 5 Pin Micro Male to 2.0 A Male Data Sync Charger Cable Converter 90 Degree Adapter SP Right 1PC) to connect the HVPS to one of the USB ports of the Raspberry Pi.
- Add the enclosure side and use 4 M3 screws to secure it to the front panel
- Connects of the components to the battery management PCB (some of the connections have already been described but are repeated here):
- P1: Place a jumper on P1 to enable charging via the USB port
- P2 brings power and logic signals to the Raspberry Pi. Use a flat cable to connect to pins 1 to 20 of the Raspberry Pi. If you use a 20-pin connector on the Raspberry Pi side, you will need to cut pins 21 and 22 of the GPIO port. You can also use a 40-pin connector and clamp the 20-wire cable on pins 1–20.
- P6 is the battery connector. To handle the high current, two wires should be connected in parallel. Pins 1 and 2 connect to the positive pole of the battery and pins 3 and 4 to the negative pole. P6 is polarised and prevents plugging the battery in the wrong way. Take care to solder P6 with an orientation matching the battery plug.
- P7 and P8 connect to 10 kΩ NTC thermistors that must be applied on the battery to monitor its temperature
- P9 is the connector for the main power switch and connects to switch 1 (image above) . To handle the large current, two wires are used for each contact, with pins 1 and 2 sending VSYS to the switch, and pins 3 and 4 receiving the return signal (c.f. Boost converter section of the battery management PCB page).
- P10 powers the LCD screen controller. 5 V is on pin 1, and GND on pin 5. It connects to connector J1 on the screenc ontroller.
- P11 powers the HVPS. 5 V is on pin 2, and GND on pin 4. 5 V connects to pins 2 and GND connects to pin 4 of the 10-pinheader on the HVPS PCB.
- P13 connects to the status LED (marked 3 in image above). It is on when the battery is charging
- P14 connects to the power good LED (marked 2 image above). It is on when the unit is connected to a source of power.
- Connect the component to the HVPS
- The right angle USB cable connects the HVPS to the Raspberry Pi
- Button 4 is the high voltage safety switch which connects to header S2 on the HVPS PCB
- LED 5 (red) indicates the presence of HV on the output, and is connected to hD3 on the HVPS PCB.
- Once everything is connected, place the bottom cover with the battery on top of the assembly, taking care that the wires are all inside the enclosure and located on the battery management side of the box (i.e. away from the high voltage side of the HVPS), and fix the bottom to the side using 4 M3 screws.
Usage of the stand-alone configuration
- Check that the safety switch (Switch 4 on figure above) is in the ‘0’ position to disable the high voltage circuit.
- Place main switch (Switch 1 on figure above) in position ‘1’ and wait until the Raspberry Pi has started.
- Start the Python interface (file install.txt in the interface main folder) has instructions to place a shortcut on the desktop, or to have the interface launched automatically on start up. The section on the Python user interface has detailed instructions on the use of the interface.
- Once you have exited the interface, you are back on the Rasbian desktop
- Don’t forget to put the HV safety switch on ‘0’ if not done already for additional safety.
- Use the desktop startup menu to shutdown the Pi
- Caution: As soon as you press the sutdown button, the LCD screen goes black. However, it takes about about 30 second for the Pi to turn off. Wait 1 minute. If you don’t do it and you switch off power too early, this can lead to corruption of files or of the SD card
- Turn off main power switch (switch 1 on figure above). Note that there is no light indicator change for this operation, so do not forget to turn off the main power, or the LCD and Pi will still be powered, which will drain the battery
A note on the battery
There is unfortunately no indication of the charge level of the battery at the moment. If you use the stand-alone HVPS for too long without connection to a power supply, it will turn off without warning you.
In case of trouble
In case of trouble with the Pi, or to update the interface or the OS, you can open the case and remove the side. It will then be possible to access the RJ45 Network plug and USB connector of the PI to connect a mouse and keyboard, and to connect your Pi to the newtwork, without disassembling everything. You can also remote access the Pi via Wifi with VNC.
The following testing procedure should be printed and marked for debugging and record keeping.
Name of testing agent:
*Assign a name and a I2C address to your board. The name and address will be stored at a later stage in the micro-controller. The name helps differentiate different HVPSs, and because they all have their own personality, and maximal voltage, we like to give them a distinctive name. The I2C address is used if you want to assemble several HVPS into a multi-channel high-voltage power supply (MHVPS). Valid addresses are between 10 and 127.
- Check all the resistor values. Place a tick in the box if the marking on the resistor matches the value below.
☐ R1 = 27R0
☐ R2 = 1500
☐ R3 = 1001
☐ R4 = 27R0
☐ R5 = 1001
☐ R7 = 1001
☐ R8 = 1500
☐ R9 = 9532 (5kV model)
☐ R9 = 8062 (3kV model)
☐ R9 = 1203 (2kV model)
☐ R9 = 8872 (1.2kV model)
☐ R9 = 2153 (500V model)
☐ R10 = 1001
☐ R11 = 1002
- Check the polarity of the components below. Place a tick in the box if the polarity matches the polarity on the PCB overlay.
- Measure the resistance between the 5V rail and GND.
How to conduct test: Use the rail board to make a connection to the 5V and ground rails using the 10-pins connector and measure the resistance with a multimeter. (If you need to build your own rail board, solder a red wire to pin 2 (5V) and a black wire to pin 4 (GND), as shown on picture below.) The switch s2 must be in position 0.
Purpose of test: To determine if there are any shorts between the power rails before applying power.
Resistance between red and black wire (Jumper h5V should be in the on position at this stage):
☐ Resistance is approximately 1.1kΩ
- Measure the output of the 5V regulator.
How to conduct test:
*Leave the rail board connected for this test*
a) Place the jumper h5v in the OFF position
b) Plug in the 7.5V adapter.
Order code: Digikey 237-2156-ND
Part number: WSX075-3200-13
Description: AC/DC WALL MNT ADAPTER 7.5V 24W
c) Measure the voltage of the regulator relative to ground. The easiest way to do this is to use the rail board from the last step to connect to ground and to probe the large tab of Reg1 with a multimeter probe. Record the voltage below.
Purpose of test: To determine if the regulator is functioning correctly without the remainder of the circuit connected.
Voltage with jumper h5v in the OFF position:
☐ Voltage is approximately 5V
- Test if the circuit has power.
How to conduct test:
*Leave the rail board and the adapter connected for this test*
a) Place the jumper h5v in the ON position
b) Observe D1
c) If LED D1 glows green, place a tick the check box and continue. If not, remove the jumper and investigate for a cause.
Purpose of test: To determine if there are any components which are consuming too much power due to assembly errors or faulty components.
☐ D1 glows green
- Test the power pin on the microcontroller header and the HV indicator LED
How to conduct test:
*Leave the rail board and the adapter connected for this test. Leave the power jumper in the ON position*
a) Insert the dummy microcontroller. The dummy microncontroller is a small board which imitates the functions of the arduino micro.
b) Ensure that the switch on the dummy microcontroller is in the ‘D3 test’ position.
c) Observe the LED on the dummy microcontroller. If the LED glows orange, place a tick in the box below. If not, remove the power jumper (h5v) and check for a cause.
d) Observe LED D3. If LED D3 glows red, place a tick in the box below. If not, remove the power jumper (h5v) and check the polarity of LED D3.
Purpose of test: Step c) tests whether the power pins on the microcontroller are connected to power. Step d) tests if the HV indicator LED is functional.
☐ The LED on the dummy microcontroller glows orange
☐ LED D3 glows red when the switch is in the ‘D3 test’ position
- Check if the high frequency switching circuit is functioning correctly
How to conduct test:
*Leave the rail board, adapter, and dummy microcontroller connected for this test. Leave the power jumper in the ON position*
a) Place a jumper on H2 in the ‘Button’ position.
b) Connect the COM port of the multimeter to the GND wire of the rail board.
c) Using a probe measure the voltage of the via close to R4. Record the voltage when S1 is depressed and when pressed.
Purpose of test: This test measures the output from Q1. The voltage must toggle from rail to rail to turn the infrared LEDs on and off.
Voltage on via close to R4 when S1 is depressed:
☐ voltage on via is ~5V when button is depressed
Voltage on via close to R4 when S1 is pressed:
☐ voltage on via is ~0V when button is pressed
- Check all the components powering the EMCO DC-DC converter
How to conduct test: *Leave the rail board, adapter, dummy microcontroller, and multimeter connected for this test. The power jumper must be in the ON position*
a) Place the safety switch S2 is in the On position (indicated on the board with a small ‘1’ to the right of the switch)
b) Ensure that the COM port of the multimeter is still connected to the GND wire of the rail board.
c) Place the switch on the dummy microcontroller into the ‘EMCO test’ position
d) Using a probe measure the voltage on pin pair 2-5 (see picture) and record the value below.
e) Place the switch on the dummy microcontroller into the ‘D3 test’ position
f) Using a probe measure the voltage on pin pair 2-5 (see picture) and record the value below.
Purpose of test: To test if the circuit providing power to the EMCO is able to provide 5V.
Voltage on pin pair 2-5 when switch is in ‘EMCO test’ position:
☐ voltage on pin pair 2-5 is ~5V when the switch is in EMCO test position
Voltage on pin pair 2-5 when switch is in ‘D3 test’ position:
☐ voltage on pin pair 2-5 is drifting towards zero when the switch is in D3 test position
If your HVPS has passed all the low voltage tests above (all check boxes ticked), you can continue with the soldering of the high voltage components (section 4 of the assembly page).
What is new?
Version 6 of the board has the exact same functionality and schematics than Version 4 (and version 5, described in the HardwareX article). The main difference is that we have modified the components so that they can all be sourced from a single manufacturer (Digikey). Ordering the components should therefore be much easier. The only components that need to be purchased seprarately are the two OC100G High voltage opotcouplers, which can be obtained from VMI, or one of their worldwide distributors.
1 Pre-assembly Procedure
- Take a PCB and clean it with isopropyl alcohol. Wear gloves during assembly.
- Refer to the bill of material available in the download section to order the required components.
- The Gerber files to manufacture the board are available in the download section. The board can be made for a few dollars from manufacturer such as JLCPCB
2 Soldering of Low Voltage Components
- Solder dual MOSFETs Q1 and Q2. Make sure that the notch on the chip is aligned with the notch on the PCB overlay.
Order code: Digikey FDS8858CZCT-ND
Part number: FDS8858CZ
Description: Dual MOSFET, N and P Channel, 8.6 A, 30 V, 17 mohm, 10 V, 1.6 V
- Solder capacitors C1, C2, and C5. Polarity is not important.
Order code: Digikey 1276-3038-6-ND
Part number: CL31A106KAHNFNE
Description: 10µF ±10% 25V Ceramic Capacitor X5R 1206 (3216 Metric)
- Solder capacitor C4. Polarity is not important.
Order code: Digikey 399-1285-1-ND
Part number: C1206C334K3RACTU
Description: 0.33µF ±10% 25V Ceramic Capacitor X7R 1206 (3216 Metric)
- Solder the resistors R1 and R4. Polarity is not important.
Order code: Digikey 408-1908-1-ND
Part number: HRG3216Q-27R0-D-T1
Description: 27 Ohms ±0.5% 1W Chip Resistor 1206 (3216 Metric) Anti-Sulfur, Automotive AEC-Q200, Moisture Resistant Thin Film
- Solder resistors R2 and R8. Polarity is not important.
Order code: Digikey CR1206-FX-1500ELFCT-ND
Part number: CR1206-FX-1500ELF
Description: SMD Chip Resistor, Thick Film, 150R, 1%, 0.25W, 1206
- Solder resistors R3, R5, R7, and R10.
Order code: Digikey 541-2245-1-ND
Part number: RCA12061K00FKEA
Description: 1 kOhms ±1% 0.25W, 1/4W Chip Resistor 1206 (3216 Metric) Anti-Sulfur, Automotive AEC-Q200 Thick Film
- Solder resistor R11.
Order code: Digikey 311-10KERCT-ND
Part number: RC1206JR-0710KL
Description: RES SMD 10K OHM 5% 1/4W 1206
- Solder resistor R9.
The value of R9 depends on the output voltage of the HVPS. Please select the appropriate value below.
For the 5kV model:
Order code: Digikey 311-95.3KFRCT-ND
Part number: RC1206FR-0795K3L
Description: 95.3 kOhms ±1% 0.25W, 1/4W Chip Resistor 1206 (3216 Metric) Moisture Resistant Thick Film
For the 3kV model:
Order code: Digikey P80.6KFCT-ND
Part number: ERJ-8ENF8062V
Description: RES SMD 80.6K OHM 1% 1/4W 1206
For the 2kV model:
Order code: Digikey P120KFCT-ND
Part number: ERJ-8ENF1203V
Description: RES SMD 120K OHM 1% 1/4W 1206
For the 1.2kV model:
Order code: Digikey 311-88.7KFRCT-ND
Part number: RC1206FR-0788K7L
Description: RES SMD 88.7K OHM 1% 1/4W 1206
For the 500V model:
Order code: Digikey 311-215KFRCT-ND
Part number: RC1206FR-07215KL
Description: RES SMD 215K OHM 1% 1/4W 1206
More details on the design of the voltage divider and the resistance values.
- Solder D1 (Green). Note the polarity! The green markings on top of the LED should face the thick line on the PCB overlay.
Order code: Digikey 67-1002-1-ND
Part number: SML-LX1206GW-TR
Description: LED, QuasarBrite, Green, SMD, 3.2mm x 1.6mm, 20 mA, 2.2 V, 565 nm
- Solder D3 (Red). Note the polarity! The green markings on top of the LED should face the thick line on the PCB overlay.
Order code: Digikey 67-1003-1-ND
Part number: SML-LX1206IW-TR
Description: LED, QuasarBrite, Red, SMD, 3.2mm x 1.6mm, 20 mA, 2 V, 635 nm
- Solder Reg1.
Order code: Digikey NCP1117ST50T3GOSCT-ND
Part number: NCP1117ST50T3G
Description: Linear Voltage Regulator IC Positive Fixed 1 Output 5V 1A SOT-223
- Solder D2. Note the polarity! The line on the diode should match the line on the PCB overlay.
Order code: Digikey 497-5574-1-ND
Part number: STPS2L40U
Description: Schottky diode, 2 A, 40 V, DO-214AA=SMB
- Solder S1. Polarity is not important
Order code: Digikey SW791-ND
Part number: B3FS-1050
Description: Tactile Switch SPST-NO Top Actuated Surface Mount
- Solder C3. Note the polarity! The line on the diode should match the marking on the PCB overlay.
Order code: Digikey 399-8415-1-ND
Part number: T491D227K016AT
Description: Surface Mount Tantalum Capacitor, 220 µF, 16 V, T491 Series, ± 10%, 2917 [7343 Metric]
- Solder L1. Polarity is not important.
Order code: Digikey 732-1701-1-ND
Part number: 7447709821
Description: 820µH Shielded Wirewound Inductor 950mA 1 Ohm Max Nonstandard
- Solder S2.
Order code: Digikey 563-1571-ND
Part number: MHS122-1
Description: Slide Switch SPDT Through Hole, Right Angle
- Solder edge connector K56GVFTRDC. The edge connector is supplied in long strips. Using a pair of pliers break off a row of 10 pins.
Order code: Digikey 2057-PH1RB-17-UA-ND
Part number: PH1RB-17-UA
Description: CONN HEADER R/A 17POS 2.54MM
- Solder h5V. Polarity is not important.
Order code: Digikey 732-5316-ND
Part number: 61300311121
Description: Pin header 3P Single row / straight / without shroud
- Solder hD1, hD3, hS1, hS2 if you intend to have components D1, D3, S1, S2 panel mounted. Polarity for these headers is not important.
Order code: Digikey SAM1121-02-ND
Part number: SSA-102-S-G
Description: SAMTEC SSA-102-S-G Board-To-Board Connector, SSA Series, 2 Contacts, Receptacle, 2.54 mm, Through Hole, 1 Rows
If you intend to place the board in the minimalistic enclosure, soldering these headers is not necessary. If you intend to place the board in the full enclosure, only headers hS1 and hS2 are necessary.
- Solder H2. Polarity is not important.
Order code: Digikey 952-2120-ND
Part number: M20-9980345
Description: Board-To-Board Connector, Vertical, M20 Series, 6 Contacts, Header, 2.54 mm, Through Hole, 2 Rows
- Solder J1.
Order code: Digikey CP-102BH-ND
Part number: PJ-102BH
Description: Power Barrel Connector Jack 2.50mm ID (0.098″), 5.50mm OD (0.217″) Through Hole, Right Angle
- Solder header sockets for microcontroller. The header sockets are supplied in long strips. Score the plastic with a craft knife and break off 17 contacts with a pair of pliers. Clean up the rough edge with the craft knife or sandpaper.
Order code: Digikey SAM1093-17-ND
Part number: SLW-117-01-T-S
Description: CONN RCPT 17POS 0.1 TIN PCB
- Prepare optocouplers OC1 and OC2. Please follow the instructions below:
Bending of the leads:
Bend the leads as shown in the series of images below.
Mark pin 1 (before painting):
Bend the tip of pin 1 so that it can be identified after painting the optocoupler.
Painting of the optocoupler:
The optocoupler is painted to prevent interference from neighbouring optocouplers and IR light which is present in the environment. Tipp-Ex is used because it creates a relatively good barrier to IR light and is easy to apply. Simply paint the plastic body of the optocoupler with a single layer of Tipp-Ex and let it dry. It is best to do it rapidly and in single strokes. Making multiple passes results in a sticky mess which is very unsightly.
Mark pin 1 (after painting):
Use a permanent pen to mark pin 1 with a dot next to the pin.
Order code: MPI Distribution AG OC100G
Part number: OC100G
Description: HV Opto-Coupler 10 kV
- Solder optocouplers OC1 and OC2. Make sure that the polarity is correct.
- Place the jumper on h5V in the ON position, and the jumper h2 in the Button position.
Order code:Digikey S9001-ND
Part number: SPC02SYAN
Description: 2 (1 x 2) Position Shunt Connector Black Closed Top 0.100″ (2.54mm) Gold
- You are ready to test the low voltage part of your HVPS
3 Testing procedure of the Low-voltage part of the HVPS
Before assembling the High-voltage components, go through the low-voltage testing procedure and ensure that the circuit is working properly. Only proceed with the assembly of the HV components if all the low voltage tests have passed.
4 Soldering of High Voltage Components
- Solder R6. Do not fully insert this resistor. Insert it so that 2mm of the leads can be seen above the top surface of the PCB.
The value of R6 depends on the output voltage of the HVPS. Please select the appropriate value below.
For the 5kV model:
Order code: Digikey SM102031006FE-ND
Part number: SM102031006FE
Description: OHMITE SM102031006FE Through Hole Resistor, Slim-Mox, 100 Mohm, 5 kV, Radial Leaded, 1 W, ± 1%, Slim-Mox Series
For the 3kV model:
Order code: Digikey SM102035005FE-ND
Part number: SM102035005FE
Description: RES 50M OHM 1W 1% RADIAL
For the 2kV model:
Order code: Digikey SM102035005FE-ND
Part number: SM102035005FE
Description: RES 50M OHM 1W 1% RADIAL
For the 1.2kV model:
Order code: Digikey 22MGBCT-ND
Part number: HHV-50FR-52-22M
Description: RES 22M OHM 1/2W 1% AXIAL
For the 500V model:
Order code: Digikey 22MGBCT-ND
Part number: HHV-50FR-52-22M
Description: RES 22M OHM 1/2W 1% AXIAL
More details on the design of the voltage divider and the resistance values.
- Solder EMCO1
EMCO1 is the DC/DC converter of the HVPS, and its voltage rating defines the maximal output voltage of the HVPS. Use the following values:
For the 5kV model:
Order code: Digikey 1470-3201-ND
Part number: A50P-5
Description: 5 kV AG Series Isolated, Proportional DC To HV DC Converter 5V input
For the 3kV model:
Order code: Digikey 1470-3200-ND
Part number: A30P-5
Description: 3 kV AG Series Isolated, Proportional DC To HV DC Converter 5V input
For the 2kV model:
Order code: Digikey 1470-3198-ND
Part number: A20P-5
Description: 2 kV AG Series Isolated, Proportional DC To HV DC Converter 5V input
For the 1.2kV model:
Order code: Digikey 1470-3192-ND
Part number: A12P-5
Description: 1.2 kV AG Series Isolated, Proportional DC To HV DC Converter 5V input
For the 500V model:
Order code: Digikey 1470-3184-ND
Part number: A05P-5
Description: 500 V AG Series Isolated, Proportional DC To HV DC Converter 5V input
- Solder the red HV socket H3
Order code: Digikey 486-3655-ND
Part number: 0040.1102
Description: Socket ø 2 mm red, 0040.1102, Schurter
- Solder the black HV socket H4
Order code: Digikey 486-3654-ND
Part number: 0040.1101
Description: Socket ø 2 mm black, 0040.1101, Schurter
5 Testing procedure of the High-voltage part of the HVPS
Once you have finished the assembly of the high-voltage components, you are ready to test the high-voltage portion of the circuit. Follow these instructions.
6 HV cables
- Cut the appropriate length of HV electrical cable.
Order code: Digikey W2722R-100-ND
Part number: 2722/22 R/C
Description: TEST LEAD 22AWG 5000V RED 100′
Order code: Digikey W2722B-100-ND
Part number: 2722/22 B/C
Description: TEST LEAD 22AWG 5000V BLACK 100′
- Manually enlarge the opening of the 2mm banana plug cover with a 3mm drill bit so it can fit over the HV cable.
Red banana plug:
Order code: Digikey 501-1318-ND
Part number: 5936-2
Description: Banana Plug Connector Miniature Solder Red
Black banana plug:
Order code: Digikey 501-1345-ND
Part number: 5936-0
Description: Banana Plug Connector Miniature Solder Black
- Solder the banana plugs to the wires and install the protective covers
- At the other extremity of the cable, install the connector you need for your application. We use Alligator clips as versatile connectors.
Order code: Digikey 36-5034-ND
Part number: 5034
Description: ALLIGATOR CLIP INSULATED RED
Order code: Digikey 36-5035-ND
Part number: 5035
Description: ALLIGATOR CLIP INSULATED BLACK
7 Next steps
The minimal enclosure is a somewhat simpler enclosure than the full enclosure. It is therefore quicker to make and to assemble. Only the high voltage side of the circuit is protected, leaving the low-voltage side exposed, for easy access to the onboard buttons and LEDs. The minimal enclosure leaves the microcontroller exposed. Accidentally pressing the reset button on the microcontroller while the HVPS is in use leads to the transient application of the full voltage at the output. Consequently, a reset button protection is placed on the microcontroller to avoid undesired activation of the reset button.
Minimal Enclosure with 3D printer
The easiest way to make the enclosure is to use a 3D printer. The Download page has a zip file containing the required STL files (3D_printing_minimal_enclosure.zip). We have tested the files with an Ender 5 FDM printer, but it should work with any printer. There is a based and a cover that can be clipped together. However, we also recommend to secure the PCB to the base and the cover to the base using screws. The base part has 5 posts, 4 of which have holes. The holes are design to accommodate a M2 metallic insert, such as this. However, the design can modified, and the hole diameter reduced to be tapped for an M2 screw. 2 screws M2x6 are used to hold the PCB on the base, and 2 screws M2x16 are used to lock the cover.
Minimal Enclosure with a Laser cutter
We use a Laser Engraver Trotec Speedy 300 to cut the parts required for the enclosure, and we have prepared files ready to be cut. We also have the Solidworks 3D files, so you can use whatever method you want to cut the parts or modify the enclosure to fit your needs.
Download the Solidworks files (Solidworks 2015): Download page –> Enclosure Files –> minimal_enclosure_Solidworks_files.zip
1.1 Enclosure Body
We use a 3 mm thick opaque PMMA for the main body of the enclosure. The file Download –> Enclosure Files –> contains all of the parts that need to be cut to assemble the main body. You need a plate of at least 220 mm x 100 mm to cut all the parts.
1.2 Front Panel
We use an engravable plastic TRANSPLY-HD with a black body and a white front layer. We use the 1.5mm-thick plates. The file Download –> Enclosure Files –> minimal_enclosure_front_panel_model.svg can be used as a base for the front panel.
The front panel is optional. It only provides text indication of the HVPS name and voltage rating.
The black filled shapes are engraved by the laser. The red and blue lines are the cut lines, matching the one on the part “Top”. We recommend that you indicate the name of the HVPS and the voltage rating (Edit the string that says Box name xx kV by the actual name and the voltage rating of your HVPS.) You can use the free space to add an image in relation with the name of your HVPS. See illustrative example at the top of the page…
A Laser works very well to engrave the panel, but is not optimal to cut the openings and external shape (ABS is not easy to cut with a Laser, because it melts). We suggest you try one of the following approaches:
- Start by cutting the openings before removing the protective cover on the top. The bits of molten ABS will land on the protective cover and will not stain the panel. Then remove the protective cover and proceed with the engraving step. The disadvantage with this method is that you need to precisely position the panel after cutting it so that the engraving match the geometry. But a very precise alignment is not required anyway.
- Start by removing the protective cover and replace it by masking tape. You can then do the three operation in one go without moving anything and in the logical order (engrave, cut red, cur blue). You must adapt the engraving parameters to go through the masking tape too. Masking tape burns without melting. This is the reason why we replace the plastic cover sheet with masking tape. Finish by removing the masking tape that will have caught the projections creating during the cutting step.
2 Assembling the parts
- Using glue for plastics (we use dichloromethane), assemble together the following parts (see picture below): Back, Front, Side (2x), Top.
Pay attention to the position of the holes in the top part, which must be on the side of the front part. Also note the orientation of the slit in the front part, as indicated on the picture.
- Place double sided tape on the topside of the top part (do not cover the 2 holes), and position the engraved front panel.
- Slide the PCB into the cover, so that the PCB tab slides into the slit of the front part. Insert the Reset protection on the ICSP header of the microcontroller to avoid undesired activation of the button.
- Insert the 4 M2 inserts into the bottom part
Alternatively, you can also tap the holes with a M2 thread, but you need to adapt the diameter of the holes before cutting the part.
- Place the 4 spacers on top of the inserts
- Place the PCB with the cover on top of the bottom part with spacers, and lock lock it in place with screws.
You need 2 M2x6mm screw on the left, and 2 M2x20mm screws on the wight to go through the cover.
1 Schematics of HVPS v6b1
2 PCB files for HVPS
2.1 Gerber files for the fabrication of the PCB
The Gerber files you need to manufacture the PCBs are on the download page
2.2 Fabrication instructions
- Type of PCB: double sided
- Dimensions of PCB: 126mm x 55mm
- Base material: 1.6 mm FR4
- Thickness of copper: 35 µm
- Soldermask: yes
- Silkscreen: only on top layer
- Surface finish: HASL
1 Required components
To perform the automatic calibration and characterisation of the HVPS, you need some equipment: a high voltage probe (preferably a model capable of measuring dynamic signals), a NI-DAQ system, and an impedance matching circuit. The different components are described in details below.
1.1 High Voltage probe
You need a HV probe to transform the high voltage output of the HVPS into a low voltage signal that can be fed to an acquisition device. The characterisation routines integrated in the GUI give the possibility to characterize the switching speed or the voltage regulation speed and stability. If you want to perform these measurements, you need to be able to measure dynamic signals. Therefore, you need a HV probe that is capable of measuring AC signals. We use a 10kV 1:1000 50MHz PR-55 probe from B&K Precision, but there are many other possibilities.
HV probes designed to be used with multimeters are suitable to perform the voltage calibration, but will not work for the other tests, because they require to measure voltage steps (i.e. the probe must have a large bandwidth).
1.2 NI-DAQ system
You need a NI-DAQ system to acquire the analogue voltage on a computer. We use a NI USB-6212 BNC, but any system will do, as long as they have at least one analogue input. The entry-level NI USB-6000 should work fine. You must be sure not to exceed the voltage rating of your DAQ system when you connect the probe to it. However, NI-DAQ systems usually accept input signals in the +/- 10 V range, and HV probe commonly have a 1:1000 attenuation. Given that the HVPS with the highest rating (5kV) will output 5000 V or less, the voltage at the DAQ input will be between 0 V and 5 V, i.e. well within specification.
1.3 Impedance matching circuit
The dynamic HV probes, such as the 50MHz PR-55 we use are designed to be connected to an oscilloscope with a 1 MOhm input impedance (and if you are using a multimeter probe, it is likely designed to be connected to a multimeter with a 10 MOhm input impedance). NI-DAQ systems have a an input impedance >10 GOhm. Connecting a HV probe directly to a NI-DAQ system will lead to erroneous readings. In addition, it is recommended that signals connected to a NI-DAQ system have a low source impedance, which is not the case with HV probes.
You need to use an impedance matching circuit as interface between the probe and the NI-DAQ. In its simplest form, the impedance matching circuit is just a 1 MOhm resistor placed in parallel with the probe.
2 High Voltage Probe calibration
2.1 Performing the probe calibration
High voltage probes have a defined attenuation ratio (most of the time 1:1000), so a calibration is not absolutely necessary. However, much better accuracy can be obtained by performing a probe calibration. To perform a probe calibration, you will need a precision HV power supply, i.e. a power supply with an output voltage that you trust as being accurate. We use a Stanford Research Systems PS350/5000V power supply for this purpose.
- Connect your HV probe to the precision HV power supply, and to the impedance matching circuit. Connect the impedance matching circuit to the NI-DAQ.
- For a set of voltages between 0 V and 5000 V (e.g. with steps of 100 V), set the HV power supply to the desired voltage value, and write down the low voltage value indicated by the NI-DAQ. NI provides tools to directly read a channel from a NI-DAQ connected to a computer so that you can read the analogue voltage. Alternatively, the HVPS interface provides the possibility to read the value of the high voltage probe from the configuration options (see screenshot). For this to work, there are two prerequisites: 1) The name of the NI-DAQ and the channel to read must be configured (see § 2.2 below), and a HVPS must be connected to the computer, or the interface main window won’t show up. The password to unlock the functions requiring the NI-DAQ is Bazinga!
- Plot the HV voltage value from the HV power supply (y axis) as a function of the low voltage value displayed by the NI-DAQ (x axis).
- Use curve fitting to find correction coefficients (see examples below)
The graph below shows the error between the voltage calculated from the probe reading using the 1:1000 factor of the probe (i.e. without custom calibration). The approximation is acceptable, but there is an appreciable error, and a non-negligible average offset.
Based on the above information, a linear fit with offset, of the form y=c1 x + c0 is fitted to the data to account for the offset and a non-perfect ratio of the probe (see graph below). The error is much smaller. However, the error is not random, but takes the shape of a parabola, due to a non-linear effect of unknown origin.
Consequently, we fit the curve with a generic 2nd order polynomial of the form y=c2 x^2 + c1 x + c0. The error for this fit is given below. The error is considerably smaller than for the linear correction and comprised within a 3 V band.
Given the previous observations, a generic 2nd order polynomial is recommended to calibrate your HV probe/impedance matching circuit/DAQ setup. The GUI interface integrates the possibility to have 2nd order polynomial to calibrate your probe. But by setting the right coefficient to 0, you can have a simple proportional calibration if you prefer. See the following section for how to enter your calibration coefficients so that your probe can be used for the automatic calibration.
2.2 Configuring the GUI to use the probe calibration
To keep the HVPS interface program as compact as possible, we have only included the components that are essential to run the program from a user point of view. This means that the LabVIEW components required to read data from a NI-DAQ system are not included, and the automatic calibration routines won’t work on a computer on which you install the interface, unless you also install NI-DAQmx, which is the package required to control NI-DAQ systems. You should have received a copy of NI-DAQmx with your hardware. Else, it can be downloaded from the NI website. You will also need the report generation toolkit to generate the excel file summarizing the results.
In the directory in which you have installed the HVPS interface, there is a folder named support. Open the file config.ini located in this folder. The first lines should look like the screenshot below:
The file allows you to enter calibration values for different probes (in case you have more than on HV probe, each with their own calibration. The probe name currently used by the programme is defined at the second line with:
where xxx represents the name you want to give to your probe, in this example it is PR55. You must then have a section in the file defining the parameters c0, c1, and c2 for your probe xxx defined by using the name of your probe in brackets, and then the 3 coefficients, each on one line:
The values of the coefficient c0 to c2 represents a quadratic fit obtained on your data from §2.1:
y = c0 + c1 x + c2 x^2
If you don’t want to calibrate your probe and want to use the ratio (e.g. 1:1000) provided by the manufacturer you can enter c0=0, c1=1000, and c2=0. If you only want a linear correction with offset, keep c2=0, etc.
In the [NI-DAQ] section you must enter the name of your NI-DAQ system (you can find that out with NI-MAX for example), and the analogue input channel to which the signal is connected. Our NI USB-6212 is called Dexter (but it hasn’t killed anybody… yet), and the signal is connected to the analogue input channel 0, so we have:
Important: The program is reading a differential voltage from the probe. On the NI USB-6212, this is totally transparent, because it is equipped with BNC connectors. However, if you are using another unit that has screw terminals, you must connect the return signal to the input which is paired with the main signal. Refer to the manual of your NI-DAQ, but most likely, you have to add 8 to the main analogue input channel. For example, if you connect the main signal to ai0, you must connect the return signal (i.e. the ground of the impedance matching circuit) to ai8.
3 Performing the automatic calibration / characterisation
After having followed the instructions of section 2 above, it is time to calibrate and characterize your HVPS:
- High Voltage enable switch (s2): off position
- Connect the SHVPS to the computer (USB + 6VDC) and launch the HVPS interface
- Connect the HV cables to the output of the HVPS.
- Take your probe and connect the low voltage side to the input of your impedance matching circuit
- Connect the end of the HV cables to the probe: black to the ground of the probe and red to the HV terminal. Ensure that the HV (red) contact is well insulated, doesn’t touch any equipment and can not be touched by someone.
- Connect the output of the impedance matching circuit to the NI-DAQ, and the NI-DAQ to your computer.
- Power on the impedance matching circuit
- High Voltage enable switch: on position
- Open the HVPS options dialog box (green square), and if necessary, enter the password (Bazinga!) in the password input field (red) (we give the password here. The intention is not to make this secure, but just to prevent the general user of the HVPS to inadvertently change its configuration)
You are now ready to perform the automatic calibration / characterisation
- Voltage Calibration
- Setting of the PID regulator coefficient
- Characterisation of the rise and fall time of the voltage regulation (not the switching!)
- Characterisation of the rise and fall time of the high speed switching
4 Measurement file
The results of each of the tests mentioned above are saved in an excel file located in the support folder of the application (usually C:\HVPS_interface\support). Here are a few important points regarding the measurement file:
- The measurement file is named yymmdd_board_name_data.xls, with yymmdd the date at which the file was initially created.
- At the end of each measurement, the data is saved in the measurement file.
- If no excel file with the name of the board being tested exists in the support folder, a new file will be created and the acquired data added to the file.
- If a measurement file with the name of the board (irrespective of the date yymmdd) is present in the support directory, the new data will be added to this already existing file.
- In this case, and if the measurement being done has already been done previously, the older measurement will be overwritten by the newly acquired data.
- The first tab (sheet) in the excel document summarizes the test which are included in the file, so that the user can see at once what are the file contents.
- The correct way to perform measurements is the following:
- Perform all the tests that you need to characterize a board (typically, and especially if this is a newly assembled board, all of them)
- Move the excel file from the support directory to a location where you archive all the measurements for future reference. It is important at this stage to move (and not copy) the file, so that the support directory doesn’t contain a file with the name of the HVPS anymore.
- If at a later stage, the same HVPS is again characterized, then a new file will be created (instead of overwriting previous data, which would happen in case the first file remains in the support folder)
- The files are generated based on an Excel template (template.xltx). The template must not be open in excel when measurements are made, or the report generation will fail. And logically, the template must not be deleted from the support directory.