Archive | Hardware

Low voltage testing procedure of SHVPS board

The following testing procedure should be printed and marked for debugging and record keeping.

Name of testing agent:

Date:

Model (kV):

Board Name*:

I2C Address*:

*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.

  1. 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
  2. Check the polarity of the components below. Place a tick in the box if the polarity matches the polarity on the PCB overlay.
    ☐ D1
    ☐ D2
    ☐ D3
    ☐ C3
    ☐ Q1
    ☐ Q2
    ☐ OC1
    ☐ OC2
  3. Measure the resistance between the 5V rail and GND.
    How to conduct test: Use the dummy microcontroller and install it on the HVPS PCB as shown on picture below (note that the side with the outline of the USB connector (two short vertical lines) goes towards the top of the PCB, and the side with the switch s1 goes towards the bottom side of the board)  With a multimeter, measure the resistance between the test points labelled ‘5V’ and ‘GND’ on the dummy microcontroller.

    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 900Ω – 1.1kΩ
  4. Measure the output of the 5V regulator.
    How to conduct test:

    *Leave the dummy microcontroller 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
    c) Measure the voltage of the regulator relative to ground. Use the ‘GND’ test point on the dummy microcontroller  to connect to ground, and 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
  5. Test if the circuit has power.
    How to conduct test:

    *Leave the dummy microcontroller 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
  6. Test the power pin on the microcontroller header and the HV indicator LED
    How to conduct test:

    *Leave the dummy microcontroller connected for this test. Leave the power adapter connected for this test. Leave the power jumper in the ON position*
    b) On the dummy microcontroller, ensure that the switch S1 is in the ‘D3’ position.
    c) Observe the LED on the dummy microcontroller. If the LED glows, 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
  7. Check if the high frequency switching circuit is functioning correctly
    How to conduct test:
    *Leave the dummy microcontroller connected for this test. Leave the power adapter 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 test point of the dummy microcontroller.
    c) Using a probe measure the voltage of the via close to R4. Record the voltage when push button 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

  8. Check all the components powering the EMCO DC-DC converter
    How to conduct test:
    *Leave the dummy microcontroller connected for this test. Leave the power adapter connected for this test. Leave the power jumper in the ON position*
    a) Place the safety switch S2 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’ position
    d) Using a probe measure the voltage on the EMCO control pin (see picture: GND probe on the GND connection of the dummy microcontroller, and positive probe on one of the two pads at the bottom right of EMCO1) 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 on the EMCO control pin (see picture: GND probe on the GND connection of the dummy microcontroller, and positive probe on one of the two pads at the bottom right of EMCO1) 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).

Full Enclosure

Warning! This enclosure design is not compatible with the PCB v6, as the power jack has changed location. Until we provide a modified design, please use the minimal enclosure for the PCB v6.

The full enclosure is a complete box that protects the SHVPS and prevents users from touching the high voltage components. The important functions (buttons and LEDs) are placed on a front panel. In the current versions, the onboard LEDs are used, but transparent light pipes guide the light to the front panel. The two buttons (High Voltage enable and push button) are mounted on the panel. Consequently, in step 18 of the assembly instructions, it is necessary to solder header hS1 and hS2, but headers hD1 and hD3 are not required.

Alternatively, you can also assemble a minimal enclosure which is simpler and easier to assemble. It only covers the HV side of the circuit, and uses the onboard switches and LEDs.

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)

1. Cutting / Preparing the parts

The enclosure is made of 3 different materials/parts

1.1 Enclosure Body

We use a 3 mm thick opaque PMMA for the main body of the enclosure. The file full_opaque_box.svg contains all of the parts that need to be cut to assemble the main body. You need a plate of at least 150 mm x 280 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. You can use any other thickness value, but the length of the light pipe (see below) must be adapted accordingly. The file front_panel_model.svg can be used as a base for the front panel.

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 “Name” X kV by the actual name and the voltage rating of your HVPS.) You can use the space below the name to add an image in relation with the name of your HVPS, and there is space for a logo on the bottom left. 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:

  1. 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.
  2. 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.

1.3 Light Pipes

The file LED_pipe.svg defines a light pipe used to guide the light from the onboard LED to the front panel. You should be cut two light pipes into a 3mm-thick transparent material (we use PMMA). You need to cut two light pipes (power LED and HV LED). The file as designed is for a front panel (see previous §) thickness of 1.5 mm. If you use another thickness for the front panel, you should adapt the length of the light pipe. It is a good idea to sand the top of the light pipe to diffuse the light of the LED on the front panel

2 Assembling the parts

  1. Using glue for plastics (we use dichloromethane), assemble together the following parts (see picture below): base, side_hv, side_hv_cache, side_jack and back.

    Base: Place the larger 3 openings on your left.
    Back: The slit must be at the bottom right.
    Side_jack: On the right. The straight side (without slots) towards the front.
    Side_hv: On the inside left. The straight side (without slots) towards the front.
    Side_hv_cache: On the outside left. The straight side (without slots) towards the front.
  2. You can slide a HVPS to check that everything is correctly positioned.
  3. Place M2 threaded metallic inserts (Tappex Multisert – Single Thickness Head – 071M2) in the parts holder and holder2.
    Note: You can replace the inserts by a threaded hole. In that case, you must modify the diameter of the holes on these parts to 1.5mm prior to cutting the parts.
  4. Glue the following parts (see picture below): top, holder and the two holder2.
    Place top so the rectangular opening is in front of you, and the 2×3 openings on your left (see image). holder goes on the left, and the two holder2 on the right. The flanges from the inserts (not shown on the picture) should be located on the inside.

  5. Place double sided tape (or glue) on the top of the front panel.
    The two large openings for the two buttons, as well as the 2 small square openings for the diode lightpipes must remain free from tape.
  6. Place the engraved front panel on top of the tape-covered top part.
    Carefully align the two parts. It may help to first place the large switch in the engravable panel, and use it as a guide. The two lightpipes can also be used to add guiding posts to perfectly align the two pieces together. Apply pressure to fix the two parts together.
  7. If not already done so at the previous step, insert the switch in the square opening.
    Order code: Farnell 4710368
    Part number: PRASA1-16F-BB0BW
    Description: TE CONNECTIVITY / ALCOSWITCH  PRASA1-16F-BB0BW  Rocker Switch, Non Illuminated, SPST, On-Off, Black, Panel, 16 A
  8. Insert the push-button in the round opening.
    Order code: Farnell 1634622
    Part number: R13-502A-05-B
    Description: MULTICOMP  R13-502A-05-B  Pushbutton Switch, Off-(On), SPST, 125 V, 3 A, Solder
  9. Insert the two light pipes in the small square openings and glue them in place from the backside.
  10. Solder wires to the the switch and push button.
    The wires for the switch should be 110 mm long.
    The wires for the push button should be 60 mm long.
    Take a wire to board connector and cut two units of two pins. Solder one unit at the extremity of each of the cables.
    Order code: Farnell 9729100
    Part number: SL 3.25.36G
    Description: FISCHER ELEKTRONIK  SL 3.25.36G  Wire-To-Board Connector, Right Angle, SL Series, 36 Contacts, Plug, 2.54 mm, Through Hole, 1 Rows
    The picture below illustrates steps 7-10
  11. Connect the wire from the push button to header hS1. Cut the wire-to-board connector of the switch to separate the two contacts, and insert the contacts into header hS2.

    The wire from the switch should go along the Arduino and between the edge of the Arduino and the power jack in the back, as shown on the image above. The two contacts should be inserted sideways into header hS2, as shown in picture below so that the wire doesn’t cover the onboard LED D1, or else you won’t be able to place the cover with the light pipe (see image below).
  12. Place the side panel (part front-removable).
    The onboard switch S2 must be in the 0 position. There is a notch in the front-removable part that prevents you from placing the part when the switch is not in the correct position.
  13. Place the front panel in place, and lock it in place with 4 plastic M2x10 screws.

High voltage testing procedure of SHVPS board

 

The testing procedure should be printed, marked and added to the other testing documents.
Report the name and I2C address from the low-voltage test sheet.

Name of testing agent:_______________________________________________________

Date:___________________________________________________________________

Board Name:______________________________________________________________

I2c Address:_______________________________________________________________

Test of the micro-controller

  1. Take a Arduino micro, but do not install it on the HVPS PCB.
  2. Open the Arduino IDE (you must have the Arduino IDE installed, as well as the required drivers for the serial communication. Refer to this page for more information)
  3. Program the Arduino with the Send_PWM program.
  4. In Arduino GUI, open the Serial Monitor.
  5. Set the termination character to “Carriage return” and the transmission speed to “115200” in the 2 dropdown lists.
    serial_monitor
  6. Check that the the onboard LED (green) is fully on
    ☐ Onboard LED is on
    uc_test_steps6_8
  7. In the serial monitor, enter 0 and press enter. The green LED should turn off, and the terminal should indicate:
    PWM set point: 0
    ADC read XXX
    (the value of XXX is not important at this stage)
    ☐ Expected values are displayed on the terminal
    ☐ Onboard LED is off
    uc_test_step7
  8. In the serial monitor, enter 1023 and press enter. The green LED’s intensity should be at 100%,  and the terminal should indicate:
    PWM set point: 1023
    ADC read XXX
    (the value of XXX is not important at this stage)
    ☐ Expected values are displayed on the terminal
    ☐ Onboard LED is on
    uc_test_steps6_8
  9. Close serial monitor, and unplug the USB cable from the Arduino.

Testing the High Voltage

Be Careful when testing the high voltage part of the circuit, as the board is not yet in a protective enclosure. High voltage will be present at the output and on some of the components during the testing of steps 6 and 7. It is important not to touch any part of the SHVPS during this test, and to place the PCB on a well-insulated surface.

  1. Insert the micro-controller into socket UC1 of the HVPS board, with the USB connector aligned with the PCB overlay
    hv_test_step1
  2. Be sure that the HV enable switch (S2) is in the 0 position
    hv_test_step2
  3. Plug the USB cable to the microcontroller
  4. Open the serial monitor in the Arduino interface (the end character and speed settings should be CR/115200, see above)
  5. Place HV enable switch (S2) on 1
  6. On serial monitor, enter 0 and press enter. Write the reading from the ADC:
    ADC Read: ___________________
    ☐ ADC Read is higher than 850 and smaller than 1023
  7. On serial monitor, enter 500 and press enter. Write the reading from the ADC:
    ADC Read: ___________________
    ☐ ADC Read is higher than 200 and smaller than 1023
  8. On serial monitor, enter 1023 and press enter. Write the reading from the ADC:
    ADC Read: ___________________
    ☐ ADC Read is smaller than 10. If not, try step 8 once again.
  9. Close serial monitor
  10. Place HV enable switch (s2) on 0
  11. Remove USB cable

Next Steps

  1. Place the jumper of header H2 in the central (onboard) position if you want to use the board with the GUI. If you want to force the use of the push button or the external pin as switching source, you can place the jumper on the appropriate position
  2. Check that the jumper of the header h5V is in the ‘on’ position
  3. Continue with the calibration of the board, and the fabrication of the enclosure.

Assembly procedure for SHVPS v4b2

1 Pre-assembly Procedure

  • Take a PCB and clean it with isopropyl alcohol. Wear gloves during assembly.

2 Soldering of Low Voltage Components

  1. 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: Farnell 1498963
    Part number: FDS8858CZ
    Description: Dual MOSFET, N and P Channel, 8.6 A, 30 V, 17 mohm, 10 V, 1.6 V
    step_1
  2. Solder capacitors C1 and C2. Polarity is not important.
    Order code: Farnell 2426964
    Part number: GRM319R61C106KE15D
    Description: SMD Multilayer Ceramic Capacitor, 1206 [3216 Metric], 10 µF, 16 V, ± 10%
    step_2
  3. Solder capacitor C4. Polarity is not important.
    Order code: Farnell 1833891
    Part number: 12063C334KAT2A
    Description: SMD Multilayer Ceramic Capacitor, 1206 [3216 Metric], 0.33 µF, 25 V, ± 10%
    step_3
  4. Solder the resistors R1 and R4. Polarity is not important.
    Order code: Farnell 2332118
    Part number: CRGH1206F27R
    Description: SMD Chip Resistor, Thick Film, 27 ohm, 200 V, 1206 [3216 Metric], 500 mW, ± 1%
    step_4
  5. Solder resistors R2 and R8. Polarity is not important. Note that R8 is vertical; do not solder it on the pad D3.
    Order code: Farnell 1795172
    Part number: CR1206-FX-1500ELF
    Description: SMD Chip Resistor, Thick Film, 150R, 1%, 0.25W, 1206
    step_5
  6. Solder resistors R3, R5, R7, and R10.
    Order code: Farnell 2307294
    Part number: ERJ8ENF1001V
    Description: SMD Chip Resistor, Thick Film, 1 kohm, 200 V, 1206 [3216 Metric], 250 mW, ± 1%
    step_6
  7. Solder resistor R11.
    Order code: Farnell 1632523
    Part number: MC1206S4F1002T5E
    Description: SMD Chip Resistor, Thick Film, 10K, 1%, 0.25W, 1206
  8. 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: Farnell 2327394
    Part number: ERJP08F9532V
    Description: SMD Chip Resistor, Thick Film, 95.3 kohm, 500 V, 1206 [3216 Metric], 660 mW, ± 1%, ERJP08 Series
    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: Farnell 2327378
    Part number: ERJP08F8872V
    Description: PANASONIC ELECTRONIC COMPONENTS  ERJP08F8872V  SMD Chip Resistor, Thick Film, 88.7 kohm, 500 V, 1206 [3216 Metric], 660 mW, ± 1%, ERJP08 Series
    For the 500V model:
    Order code: Farnell 2327103
    Part number: ERJP08F2153V
    Description: PANASONIC ELECTRONIC COMPONENTS  ERJP08F2153V  SMD Chip Resistor, Thick Film, 215 kohm, 500 V, 1206 [3216 Metric], 660 mW, ± 1%, ERJP08 Series
    More details on the design of the voltage divider and the resistance values.
    step_8
  9. 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: Farnell 2062262
    Part number: SML-LX1206GW-TR
    Description: LED, QuasarBrite, Green, SMD, 3.2mm x 1.6mm, 20 mA, 2.2 V, 565 nm
    step_9
  10. 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: Farnell 2062231
    Part number: SML-LX1206IW-TR
    Description: LED, QuasarBrite, Red, SMD, 3.2mm x 1.6mm, 20 mA, 2 V, 635 nm
    step_10
  11. Solder Reg1.
    Order code: Farnell 1825292
    Part number: AP1117E50G-13
    Description: Fixed LDO Voltage Regulator, 6.4V to 18V, 1.2V Dropout, 5Vout, 1Aout, SOT-223-3
    step_11
  12. Solder D2. Note the polarity! The line on the diode should match the line on the PCB overlay.
    Order code: Distrelec 170-15-894 (old order code: 60 57 24)
    Part number: STPS2L40U
    Description: Schottky diode, 2 A, 40 V, DO-214AA=SMB
    step_12
  13. Solder S1. Polarity is not important
    Order code: Farnell 3121185
    Part number: B3FS-1050
    Description: Tactile Switch, Non Illuminated, 24 V, 50 mA, 0.98 N, Solder, B3FS Series
    step_13
  14. Solder C3. Note the polarity! The line on the diode should match the marking on the PCB overlay.
    Order code: Farnell 2473573 (old order code 1793889)
    Part number: T491D227K016AT
    Description: Surface Mount Tantalum Capacitor, 220 µF, 16 V, T491 Series, ± 10%, 2917 [7343 Metric]
    step_14
  15. Solder S2.
    Order code: Farnell 674357
    Part number: 09-10290-01
    Description: Slide Switch, SPDT, Through Hole, 500 mA
    step_15
  16. 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: Farnell 9729100
    Part number: SL 3.25.36G
    Description: Wire-To-Board Connector, Right Angle, SL Series, 36 Contacts, Plug, 2.54 mm, Through Hole, 1 Rows
    step_16
  17. Solder h5V. Polarity is not important.
    Order code: Distrelec 300-24-522 (old order code: Farnell 1022245)
    Part number: 61300311121
    Description: Pin header 3P Single row / straight / without shroud
    step_17
  18. 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: Farnell 1668221
    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.
    step_18
  19. Solder H2. Polarity is not important.
    Order code: Farnell 1022230
    Part number: M20-9980345
    Description: Board-To-Board Connector, Vertical, M20 Series, 6 Contacts, Header, 2.54 mm, Through Hole, 2 Rows
    step_19
  20. Solder J1. 
    Order code: Farnell 1200151
    Part number: NEB/J 25 R
    Description: DC Power Connector, Jack, 1 A, 2.35 mm, Through Hole Mount
    step_20
  21. 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:  Farnell 2396216
    Part number: 929974-01-36
    Description: Board-To-Board Connector, 929 Series, 36 Contacts, Receptacle, 2.54 mm, Through Hole, 1 Rows
    step_21
  22. Solder L1. Polarity is not important.
    Order code: Distrelec 158-00-420 (old order code: 335529)
    Part number: ELC16B821L
    Description: Inductor, radial 820 uH 0.88 A ±10%, Panasonic Automotive & Industrial Systems
    step_22
  23. 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.
    bending_oc
    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 inteference 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.
    METADATA-START
    Order code: MPI Distribution AG OC100G
    Part number: OC100G
    Description: HV Opto-Coupler 10 kV
  24. Solder optocouplers OC1 and OC2. Make sure that the polarity is correct.
    step_24
    (unlike what is shown on the picture above, the EMCO DC/DC converter and resistor R6 are not yet soldered)
  25. Place the jumper on h5V in the ON position, and the jumper h2 in the Button position.
    Order code: Farnell 9728961
    Part number: CAB 4 GR
    Description: Jumper (Busbar), Jumper, 0.6 to 0.64mm Wire Wrap Pins and 0.6 to 0.7mm Dia, 2 Ways, 2.54 mm
    step_24
  26. 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

  1. 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: Farnell 1550763
    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.
    hv_step_1
  2. 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: EMCO/Condatas A50P-5
    Part number: A50P-5
    Description: 5 kV A Series Isolated, Proportional DC To HV DC Converter 5V input
    For the 3kV model:
    Order code: EMCO/Condatas A30P-5
    Part number: A30P-5
    Description: 3 kV A Series Isolated, Proportional DC To HV DC Converter 5V input
    For the 2kV model:
    Order code: EMCO/Condatas A20P-5
    Part number: A20P-5
    Description: 2 kV A Series Isolated, Proportional DC To HV DC Converter 5V input
    For the 1.2kV model:
    Order code: EMCO/Condatas A12P-5
    Part number: A12P-5
    Description: 1.2 kV A Series Isolated, Proportional DC To HV DC Converter 5V input
    For the 500V model:
    Order code: EMCO/Condatas A05P-5
    Part number: A05P-5
    Description: 500 V A Series Isolated, Proportional DC To HV DC Converter 5V input
    hv_step_2
  3. Solder the red HV socket H3
    Order code: Distrelec 140-21-352
    Part number: 0040.1102
    Description: Socket ø 2 mm red, 0040.1102, Schurter
    hv_step_3
  4. Solder the black HV socket H3
    Order code: Distrelec 140-21-351
    Part number: 0040.1101
    Description: Socket ø 2 mm black, 0040.1101, Schurter
    hv_step_4

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

  1. Cut the appropriate length of HV electrical cable.
    Red wire:
    Order code: Digikey W2722R-100-ND
    Part number: 2722/22 R/C
    Description: TEST LEAD 22AWG 5000V RED 100′
    Black wire:
    Order code: Digikey W2722B-100-ND
    Part number: 2722/22 B/C
    Description: TEST LEAD 22AWG 5000V BLACK 100′
  2. 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: Farnell 1699020
    Part number: 25.205.1
    Description: MULTICOMP  25.205.1  BANANA PLUG, 10A, 2MM, CABLE, RED
    Black banana plug:
    Order code: Farnell 1699021
    Part number: 25.205.2
    Description: MULTICOMP  25.205.2  BANANA PLUG, 10A, 2MM, FREE, BLACK
  3. Solder the banana plugs to the wires and install the protective covers
  4. At the other extremity of the cable, install the connector you need for your application. We use Alligator clips as versatile connectors.
    Red Clip:
    Order code: Digikey 36-5034-ND
    Part number: 5034
    Description: ALLIGATOR CLIP INSULATED RED
    Black Clip:
    Order code: Digikey 36-5035-ND
    Part number: 5035
    Description: ALLIGATOR CLIP INSULATED BLACK

7 Next steps

Once you have finished assembling and testing (Low voltage testing, High voltage testing) your HVPS, you should place in in a safe enclosure and proceed with configuration/calibration.

Resistance Ratios for the high-voltage resistive divider

The output voltage is read by the SHVPS by way of a resistive divider. The SHVPS micro-controller (Arduino micro) has a 10 bit analog-to-digital converter (ADC) which maps an input voltage from 0 V to 5 V into a value between 0 and 1024. The resistive divider should therefore divide the maximal output voltage by a given ratio, so that an output value of 5 V is obtained when the SHVPS is at its maximum voltage rating (for example, the ratio would be 1:1000 for a 5kV unit). In practice however, we have chosen to use slightly higher ratios, so that the voltage on the ADC input is roughly at 4.8 V when the SHVPS is delivering its full output voltage. This prevents the ADC from saturating, should the output raise higher than the maximal rating of the HVPS, and therefore allows detecting (and dealing with) this eventuality.

Furthermore, once the ratio is defined, it is necessary to choose the values of resistances to use. We have noticed that the current “wasted” in the voltage measuring circuit, has a strong influence on the ability of the EMCO DC/DC converter to rapidly change its output voltage. The more current going through the circuit, the faster the response to a voltage set point change. However, this means less current available for the load. We have tested different resistance combinations and the optimal values for a few EMCO Series A models are given below:

EMCOR6 (MΩ)R9 (kΩ)RatioFb Volt. @ Vmax (V)C1HV Resistor #LV Resistor #
5kV10095.310504.761.05031550763 (Farnell)
2327394 (Farnell)
3kV5080.66214.831.0356SM102035005FE-ND (Digi-Key)P80.6KFCT-ND (Digi-Key)
2kV501204184.791.0442SM102035005FE-ND (Digi-Key)P120KFCT-ND (Digi-Key)
1.2kV2288.72494.821.037622MGBCT-ND (Digi-Key)2327378 (Farnell)
500V222151034.841.033322MGBCT-ND (Digi-Key)2327103 (Farnell)

Columns description:

  1. EMCO: The voltage rating of the EMCO to be soldered on the board
  2. R6: Value of resistance R6 (HV resistor)
  3. R9: Value of resistance R9 (LV resistor)
  4. Ratio: relation between the total (HV) voltage applied to the divider and the low voltage output (i.e. (R9+R6)/R9)
  5. Fb Volt. @ Vmax (V): Feedback voltage (i.e. voltage applied on the ADC pin) when the EMCO is delivering its full output voltage. This the EMCO rating (col 1) divided by the ratio (col 4).
  6. C1: This is the theoretical correction factor assuming linear relationship between the true HV output and the value read by the ADC. This value can be used as calibration for the HVPS, using C0=0, C2=0, and setting C1 to the value given in this table. However, this is not recommended, and a full calibration should be done in order to have a good voltage accuracy over the complete voltage range of the HVPS. The value in this column is obtained by dividing 5 (i.e. the full scale voltage of the ADC) by the result of col 5.
  7. HV Resistor #: This is the order number (and retailer) for the HV resistor
  8. LV Resistor #: This is the order number (and retailer) for the LV resistor