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B efore commencing assembly, you will need to choose your USB-PD module to connect via CON5. We recommend our unit based on the AP33772S chip, as long as you have a suitable power supply that provides a PPS output, since the HUSB238-based module does not support PPS. Our article in the previous issue discusses these two modules in detail. You’ll also need a USB-C power supply that supports USB-PPS or USB-PD. We found several units from Ikea’s SJÖSS range that we thought were good value (siliconchip.au/link/acct), although some of them only support USB-PPS up to 16V with a USB-PD (fixed) profile for 20V. We used these for much of our testing. We even found a power bank that supports USB-PPS up to 11V and USB-PD up to 12V. With a suitable power bank, the USB-C PSU does not need to be tethered to a mains connection. Note that like other PSUs without a direct mains connection, the USB-C PSU does not have an Earth connection. You can use a simple DC source if you like. While it won’t be very efficient, it will no doubt be useful in low-current scenarios. If you are using a different enclosure than specified, we suggest you use the bare PCBs to plan and mark out the required holes. There are three mounting holes on the main PCB that can be used to attach M3 hardware. The front panel has 2.5mm holes to suit the fittings included with your chosen enclosure. You could also copy and use the overlay diagrams (Figs.5 & 6) as templates. Construction The main PCB will require the most work since it contains most of the components; it measures 73 × 77mm and is coded 04107261. If you need to program the microcontrollers (IC3 and IC4) in-circuit, keep in mind that some of the programming pins are also used at runtime and are connected to components that may interfere with programming. In that case, we recommend having a look at the next section on PIC programming before starting construction, so you can avoid that problem. If you have pre-programmed chips, no programming step is necessary. There is also the option to program siliconchip.com.au Mighty USB-C Part 2 / 2 Bench PSU We introduced our design for the Mighty USB-C Bench PSU last month, which uses modern USB-C power delivery technology to provide a variable power source and allow efficient operation at different output voltages. Its is designed to reduce the needs for obscure parts, while providing a comprehensive user interface. By Tim Blythman Delivers up to 20V at 2A (if the USB power source is capable) Compact case measures 94 × 83 × 30mm Detailed OLED display plus LED status Rotary encoder for tactile voltage and current control Highly configurable for efficiency or low-noise operation Software features include fuse emulation Detailed USB-PD source information the chips out-of-circuit if you have suitable hardware. You’ll need something like the PIC Programming Adaptor from September 2023 (siliconchip.au/ Article/15943) combined with appropriate SMD-to-DIP adaptors. That article has information about obtaining suitable adaptors. The front panel PCB is fairly compact, so we recommend you keep the enclosure on hand to check that Australia's electronics magazine everything fits as you go. Most of the checks and calibrations should be performed before the unit is secured into the case so that the test points can be accessed. That will require all parts to be fitted and the panel PCB to be connected to the main PCB. Once everything has been checked and calibrated, Q1 and the thermistor need to be affixed to the enclosure using an insulated mounting kit. After November 2026  75 the rear panel is fitted, the PCB is fastened to it using a machine screw. This ensures that the main PCB does not shift and flex Q1’s leads. PIC programming There are two main things to consider if you need to program the PICs in-circuit (after soldering them). Firstly, there are two different chips that run different firmware, so ensure that you don’t mix them up. Also, some of the programming pins have shared roles that might interfere with programming if they are connected to parts of the circuit that will load them. The overlay diagram, Fig.5, shows the components that are necessary for programming marked in blue dashed rectangles. The 10kW resistor and 100nF bypass capacitor for each IC are the minimum parts needed for correct operation, while the CON3 and CON7 headers are needed to connect the programmer. So the simplest approach to programming IC3 and IC4 in-circuit is to fit only these parts first, program the chips, then fit the remaining parts. You’ll also need a suitable programmer, such as a PICkit 4, PICkit 5, Snap or PICkit Basic, plus a power supply if your programmer cannot provide ‘target power’. 5V power can be applied between the TP1 ground test point and the TP3 5V test point. Anything between around 3V and 5V (eg, a 3V coin cell or a pair of 1.5V alkaline cells) should be sufficient for programming. Start with IC4, which is programmed via CON7. Connect the programmer, ensuring that the pin 1 chevron markers are aligned. IC4 is an 8-pin PIC16F18115 and should be programmed with the 0410726B.HEX file; the other hex file should be too large to work. Open the MPLAB IPE, select the part number, connect the programmer (and power supply if needed). Press Connect and ensure communication is working and the chip is identified. Load the HEX file, then perform the Program and Verify steps. Next, program the 20-pin IC3 (PIC16F18146) using a programmer connected to CON3 and the 0410726A. HEX file. It should be possible to program IC3 with all components fitted, but we recommend doing it beforehand in case there are any problems later. Verify the programming, 76 Silicon Chip Like the main PCB, we used a header on the front panel for ease of disassembly. See how we soldered the rotary encoder’s leads and used a short solid-core wire to secure the free end of the OLED module. then disconnect all programmers and power supplies before resuming assembly. Main PCB construction There are many SMD parts in this project, so ensure you have the requisite SMD gear, such as flux paste, solder-­ wicking braid, tweezers and fume extraction. Magnifiers and good illumination are also very helpful. Start with the finer-pitched parts, such as IC1-IC4, REG1 and Q2-Q5. Check each part’s polarity and be sure not to mix up similar parts. All the small transistors come in the same package. Q2-Q4 are BC817 types, while Q5 is a 2N7002 and REG1 is an MCP1700 – all in the same SOT23 package. IC1 is also in the same SOIC-8 package as IC4. Find their locations and orientations on the Fig.5 overlay diagram. Apply flux to each component’s PCB pads, rest each in place and adjust with tweezers. Tack one lead and make sure all the leads are aligned with their pads and the part is flat against the PCB before soldering the remaining leads. Use solder-wicking braid (with extra flux) to draw up any excess solder that results in a bridge between adjacent pads. Follow by fitting diodes D1, D2, D4, D5 and regulator REG2, paying close attention to their polarity and orientation. Note that D4 and D5 face in opposite directions. If you have the surface-mounting version of RLY1, solder it next. Note the bar at one end, which should align with the pin 1 marker dot. Now we can work through the passives according to the parts list and Fig.5. Solitary inductor L1 is not polarised; nor are any of the capacitors. There should be enough space to solder each set of components with the same value without worrying about other parts getting in the way. We suggest starting with the capacitors, since they will not have markings on their bodies, then follow with the resistors. Most of the passives are M3216 (imperial 1206) size at 3.2 × 1.6mm, except for the larger 50mW current shunt resistor. All the SMD parts should now be affixed to the main PCB. It is then a good time to clean off any excess flux using an appropriate solvent. Inspect for bridges and dry joints and rectify as needed. When the main PCB has dried, solder in the fuse clips. You can Fig.5: the main PCB is mostly a straightforward SMD design. If you need to program the microcontrollers in-circuit, you should initially only populate the components in the dashed blue rectangles. You can add the others after programming. Australia's electronics magazine siliconchip.com.au Fig.6: using a PCB as a panel makes for an elegant result but sometimes requires some unusual assembly steps; the OLED module is mounted upside-down using short stubs of wire. Check the clearances with the enclosure during the assembly of this PCB, since the spaces around the OLED module and rotary encoder are quite tight. insert the fuse to ensure the clips are aligned correctly. If RLY1 is a through-hole type, solder it now. Fit Q1 next, with its leads soldered at the very tips and in the orientation shown by the silkscreen markings. Ensure it is mounted squarely to the PCB. Leaving a good amount of lead attached will allow the body of the transistor to be positioned in the enclosure. Have a look at the photos to confirm the arrangement. Note how Q1 has been bent over to near its final position. Once inside the case, the top surface of Q1 is approximately 16mm from the top surface of the PCB. To secure the main PCB inside the enclosure, we have provided a rectangular pad to which an M3 nut can be soldered, adjacent to TP4. The nut will need to be nickel- or zinc-plated, or made of brass, to allow soldering. Ensure that the nut is aligned parallel to the edge of the PCB and take care not to get any solder on the internal threads. If you don’t have a suitable PCB holder, you could slide the PCB partway into the enclosure to support it level and allow access to the underside of the pad. Solder the nut in place and try to get some solder up the sides to form a solid fillet. You can now solder the UBS-PD or USB-PPS module to CON5. We fitted the module under the main PCB to allow room for the thermistor lead to reach Q1. This also keeps the opening for the USB-C lead close to the bottom of the unit. Use the male pin headers, and leave a slight gap above the USB-C socket’s shell so it doesn’t touch the PCB to avoid damage to the solder mask. Trim the leads under the module so that they are well clear of the enclosure. You could solder lead offcuts or other solid-core wire to secure the mounting holes near the USB-C socket. You can now connect a USB supply to the module and check some of the voltages at the test points. Use TP1 as the negative connection for your multimeter. TP4 should be close to 5V, while TP3 will be sitting around 4.7V due to REG2’s dropout voltage. Both of these should be within 0.3V of these values. If not, disconnect the power and double-check everything. TP2 should be between 9V and 11V, probably just under 10V. If this is correct, then IC3 and IC4 are correctly programmed. If you are using a DC supply over 5.5V, there should be a nominal reading at TP4, with TP3 close The location of Q1 and the thermistor is close to that shown here, although the lid of the enclosure and the insulating pad would obscure everything below the head of the screw. The USB-C module mounts under the main PCB to assist with clearance for the thermistor wiring. We fitted headers to our prototype for testing, but we expect constructors will use fixed wiring soldered to the PCB. siliconchip.com.au Australia's electronics magazine to 5V. TP2 should be about 5V higher than TP4, since the default is for the OA+ boost supply to run. Disconnect the power for now and move onto the front panel PCB. Front panel PCB The 0.8mm-thick black front panel PCB is coded 04107264 and measures 29 × 89mm. Before commencing assembly, check if you need to drill out the holes for the output connections. We used rubber grommets to protect wires fed through these holes, but you could drill them out to fit banana sockets or binding posts if you prefer. It will be easier to drill these before the components are fitted. Be sure that there is enough room to fit the hardware, as the panel is quite small. Also take care not to damage the PCB finish or rip any traces off. Drilling the fibreglass PCB should be done with ventilation and respiratory protection. We recommend working outside with a face mask. Test-fit the sockets and ensure that there is clearance to the remainder of the enclosure. Fig.6 is the overlay diagram for the front panel PCB. It has several components fitted in an unusual fashion, so take a close look at the photos and diagram to ensure that everything is installed correctly. Keep the enclosure at hand to check your clearances. Fit IC101, being sure to align the pin 1 dot on the silkscreen to that on the part. Follow with LED101, noting that its dot is in the opposite direction. This part is quite sensitive to heat, so don’t dwell too long with the iron. Follow with the 100nF capacitor and 1kW resistor. Clean off any excess flux. Solder the tactile switches next, with their stems protruding down through the holes. Tack one lead and take time to align each switch stem centrally within the hole. Since the stem and hole will be visible, any misalignment will be apparent. Solder the remaining leads once the position is correct. November 2026  77 Placing the USB-C module underneath the PCB helps with clearance for the thermistor wiring. The nut near Q1 is soldered to the PCB and helps to hold it in place relative to the enclosure so that Q1’s leads don’t flex. The final position of Q1 is very close to what is shown here. This requires the very tips of Q1’s leads to be soldered to the PCB and a bend formed near where the leads exit the body of the transistor. 78 Silicon Chip Australia's electronics magazine To fit the rotary encoder, remove the screw and washer, then carefully bend the leads over so that they will reach the PCB when the encoder is fitted. Use the screw and washer to secure the encoders to the panel. Check the alignment and ensure that it is within the silkscreen markings. When all is well, solder each lead to its corresponding pad. To fit the OLED module, form short pieces of solid-core wire into an L shape. The shorter part of the L should fit within the MOD101 pads. Using tweezers, solder each piece of wire to its pad, with the wire pointing upwards from the centre of the marked outline. Remove the protective film and any headers from the OLED module and ensure the holes are clear, then thread this over the L-shaped wires on the panel PCB. Push the module flat against the panel PCB and gently adjust it as needed to align it with the silkscreen outline. Solder each wire to its corresponding pad and then trim neatly. The single pad between MOD101 and RE101 can be used to solder a short length of wire to secure the other end of the OLED module. Check our photos to see how it should look. The next step will be to connect the two PCBs using hookup wire or similar. Each wire should be about 4-5cm long. Prepare the six wires and solder each one to the back of the panel PCB. Each wire can then be soldered directly back to its matching counterpart on the main PCB. The silkscreen markings can be checked if there is any confusion. The USB-C PSU is now functionally complete, but you will also need to install the thermistor so that no fault is detected. Temporarily screw the thermistor to Q1 so that you can work out the lead length before cutting; our prototype was cut to about 12cm in length. Then bare the leads and solder them directly to the CON4 pads. The thermistor is not polarised. You can leave the thermistor in place for now so that it can detect any thermal problems before final assembly is complete. The thermistor should be insulated from the lug by the potting compound, but you can check this with a multimeter. Testing and calibration Hold one of the panel switches siliconchip.com.au down and apply a USB-C power supply to the CON5 module. The display should light up and show a message as the LED lights up red. If the display shows a “Checking panel” message for more than a second, the front panel PCB may not have been recognised. In that case, check the soldering around IC101 and the wiring back to CON1. The message should show “Panel at: 0x20” for a PCF8574 or 0x38 if a PCF8574A is used. The second line should show that either a HUSB238 or AP33772S was found and indicate the number of USB-PD PDO profiles that were detected. If this shows “DC source” when a USB source is connected, the USB-PD module may not be detected; check the module. Release the switch to allow the software to proceed past this screen. The display should show something similar to Screen 1. If nothing is seen on the display, check the wiring to MOD101. All the displayed values should be sensible. The setpoints and actual values should start out at zero, the temperature shown should be around ambient and the voltages on the bottom line should be about 5V and 4.7V as per TP4 and TP3 earlier. The “L” current-limiting indicator will probably be on, since the current setpoint will be 0A. Controls On the main screen, the rotary encoder controls the voltage or current setpoint according to which is selected by the angle brackets on the first line. Toggle between the two by pressing the rotary encoder to activate its internal switch. Pressing the UP or DOWN buttons should activate or deactivate the relay. When the relay is energised, the LED shows green. If a fault occurs, it is shown on the first line of the display, the relay is switched off and the voltage is forced to a setpoint of 0V. Pressing DOWN will reset the fault indication as long as the fault itself has been cleared. For example, if there is a temperature diately saved to non-volatile memory. There is a setting screen (Screen 7) that can be used to save any changes you’ve made or restore the settings to their defaults. In Settings, the UP and DOWN buttons usually have the same effect as the rotary encoder, although some screens use them for different purposes. #1 PDO listing (Screen 2) Here you can view information about the power data objects supported by your USB power source. Use the rotary encoder to cycle between them. Pressing UP or DOWN will refresh the source PDO listing. If you see NO PDO shown here, the source is not PD-compatible or it couldn’t be detected. A legacy 5V USB or fixed DC source will also show this indication. The specifications of the USB-C we used for much of our testing. Its USB-PPS profiles only allow up to 16V, with a USB-PD profile needed for higher voltages, up to 20V. Source: www.ikea.com fault, the temperature must return to the normal range before the PSU can be reset. For a current trip, you may need to adjust the current setpoint to be above 0A. If multiple trips occur, only one is cleared at a time. This allows you to see if multiple faults have occurred. Pressing the rightmost NEXT button (>) will enter Settings, as long as the output relay is off; you will see the LED flashing if you attempt to enter Settings with the relay on. Each Settings screen is numbered at upper left for ease of navigation. In Settings, the rotary encoder button will go BACK to the previous Settings screen, while the NEXT button will move to the next and then loop around to the main screen. See below for the full range of settings and calibration factors. As long as you have the thermistor connected and mounted to Q1, you can run your own tests on the USB-C PSU assembly to check its operation. The thermistor will detect if Q1 starts overheating. Settings Screens Changes to settings are applied immediately, but they are not imme- #2-5 Operating options (Screen 3) These screens show several operating options that can be toggled by pressing UP or DOWN, or turning the rotary encoder. #2 V Tracking This dictates whether the USB-PD target voltage follows the setpoint or the actual output voltage. The default is to follow the setpoint, which will generally mean a fast response to changes, but lower efficiency (more dissipation) if current limiting is occurring, since the setpoint will be higher than the output voltage in that case. #3 Current mode This determines whether a current-­ limiting event will also switch the relay off. The default mode is simple current limiting. Enabling a trip will cause the relay to open if the current limit is reached. #4 Current set limiting This forces the current limit setpoint to ramp down if it exceeds the capabilities of the active PDO. It is on by default; if switched off, it may result in the power source shutting down if too much current is drawn. 2 3 Screen 1 (left): the main control screen is full of information about the USB supply and transistor temperature, as well as the voltage and current readings you might expect. siliconchip.com.au Australia's electronics magazine November 2026  79 #5 Load last setpoint This causes the voltage and current setpoints to be reloaded at startup. During operation, these are saved to EEPROM within ten seconds if they have changed. The default is to reload these values at startup, but this can be disabled, in which case the setpoints will be set to 0V and 0A at startup. The relay state is not stored; it always starts in the off state. The Mighty USB-C Bench PSU is compact, versatile and easy to use. #6 Temperature Alarm This sets the thermistor temperature at which the temperature display on the main page will start flashing as a warning. All temperatures are displayed in degrees Celsius (°C). #7 Temperature Shutoff (Screen 4) This sets the (higher) temperature at which the output will be disconnected. It’s also possible for an open-circuit thermistor to cause it to trip; this is indicated in the fault message. #8 Voltage Headroom (Screen 5) This sets the amount by which the USB-PD source voltage must exceed the target voltage (decided by #2 V Tracking). A lower value will be more efficient, but may result in a sluggish response to changes if the actual voltage is chosen as the target. Values down to 0.3V should work well as long as the OA+ boost is active. If OA+ boost is switched off, then this may need to be increased (up to 5V) to ensure that the voltage setpoint can be reached. #10 Op amp supply boost (Screen 6) This sets the duty cycle of the PWM supplied to the OA+ supply boost circuit. A value of 0% shuts down the boost circuit (for low-noise operation). The default value of 6% was sufficient to provide 5V of headroom in our testing, but this can be adjusted up to 15% as needed. #11 NV memory (Screen 7) This is effectively an estimate of the quiescent current used by the PSU. It is deducted from the current available from the USB-PD source to calculate how much current is available for the output. The default is 200mA, meaning that a 1.5A source will be limited to a setpoint of 1.3A at the output. This gives the option to save all live settings and calibration values to EEPROM, so they will be reloaded at the next startup. This is done by pressing DOWN. Pressing UP will restore the live and EEPROM settings from a backup in flash memory, so can be used if the settings are corrupted. A successful save or restore will be shown as a message on this screen. After the NV memory screen, the 4 5 #9 Current Headroom 10 remaining settings are mostly for calibration and should not need to be changed after initial setup. Remember to go back and save the following calibration values on the NV memory screen to ensure that the updated values are loaded at boot. #12 & #15 Calibration instructions (Screen 8) These give instructions for the use of the voltage (#13-14) and current (#16-17) calibration screens that follow. Continuing from this screen will activate the relay and output according to preset parameters, so you should only connect a multimeter set to either volts or amps as appropriate. #13-14 Voltage calibration (Screen 9) These pages switch on the relay and 6 12 11 80 Silicon Chip Australia's electronics magazine siliconchip.com.au set the voltage and current limit to suitable levels for trimming the offset (#13) and scale (#14) of the voltage calibration. Ensure that the two displayed voltage values match, then connect a voltmeter to the output. Adjust the offset or scale displayed on the second line until the voltage values match the voltmeter. #13 delivers a voltage near 0V to best trim the offset, while #14 delivers a higher value to allow the scale to be adjusted. The two values interact to a small degree, so it is best to check back on each and make small adjustments until both are satisfactory. #16-17 Current calibration (Screen 10) These are similar to #13-14 except they work with current and thus expect an ammeter to be connected. Ensure that the setpoint and actual values shown match. This means that the PSU output will be current-limited. Be aware that a high current draw will likely cause Q1’s temperature to rise, so if a thermal trip occurs, you can return to #15 to reset the fault. Like the voltage calibration, the two values will interact to a degree, so you should perform a few calibration iterations to confirm the values are correct. thermometer. Switch to the scale (#19) page and apply a high temperature; around 60°C will be sufficient. Adjust the scale to match the reading on the thermometer. Recheck the values to confirm that they are accurate. #20-22 Other voltage calibrations (Screen 12) These voltage measurements do not require an offset, so they can be calibrated by a simple scale value. Use a multimeter to measure the voltage and adjust the calibration parameter until the measured voltage matches the display. Use TP2 (relative to TP1 ground) for #20 OA+, TP3 for #21 +5V and TP4 for #22 IN+. None of these are critical to the operation of the PSU, since they are simply used for warning alerts and user feedback. They will be accurate to within a few percent without calibration. #23 DC Limit (Screen 13) If a DC supply is used, this should be set to the maximum working current of the DC supply. The value is used by the USB-C PSU to calculate the upper limit that the current can be set to if the current setpoint limiting is enabled. the absolute value of the configuration value. #25-26 Calibration setup (Screen 15) The values shown on these screens set the voltages and currents used for the #12-17 calibration steps. They are the raw DAC values that are used to set the voltage and current when the relay is activated, so they should not need to be changed at all. The LO value on the left is set by the rotary encoder, while the HI value on the right is set by the UP and DOWN buttons. In general, the LO values are used for offset factors, to allow the variable to be trimmed close to zero. The HI voltage value is used for the voltage scale factor, with the current set to LO, since a voltmeter will present no load. Similarly, the HI current value is used for the current scale factor, with the voltage set to the LO value, since an ammeter will effectively present a short circuit and require negligible voltage at the output. As long as the voltage and current values on #12-17 are able to be achieved, there is little to no reason to change the values on #25-26. Enclosure These calibrations will probably be unnecessary unless you have a vastly different thermistor, so we don’t recommend changing them otherwise. Like the voltage and current calibration, the temperature is calculated using scale and offset values. For this calibration, you will need an accurate thermometer and a way of changing the temperature of the thermistor over a wide range. Apply a low temperature (around ambient) and adjust the offset (#18) so that the reading matches the This is used to set the direction and steps per detent of the rotary encoder. The UP and DOWN buttons change the configuration value, while rotating the encoder will be reflected in the TEST display. A movement of one detent clockwise should cause the test value to increase by one. Make sure to rotate for several detents to check that there are no missed or extra steps due to rounding. If the movement is backwards (a clockwise motion decreases the value), the sign of the configuration value should be flipped (eg, from -4 to 4). If the test value changes too much, decrease Once you have completed the calibration, disconnect the power supply and unscrew the thermistor from Q1. Bend Q1 over as shown in the photos to allow the PCB to fit into the enclosure. Adjust it so that you can check where the screw will need to be fitted. You will need a hole in the top of the enclosure to attach Q1 for heatsinking, plus two on the back panel, one for the USB-C socket of the USB-PD module and another to thread the screw for securing the PCB. We have provided a drilling diagram (Fig.7) matching our prototype, but you might like to use your assembled PCB to mark out where the holes 7 8 9 13 14 15 #18-19 Temperature calibration (Screen 11) siliconchip.com.au #24 Encoder setup (Screen 14) Australia's electronics magazine November 2026  81 need to be. In particular, it might be better to drill the hole for Q1 to suit its actual location. The panels and enclosure are quite thick but made of fairly soft aluminium. Make sure that the hole for Q1 has no burrs that might short out to its tab, since this will be live at the POWER+ voltage. The easiest way will be to rub a small piece of sandpaper over the inside of the hole and be sure to wipe away any residue. If you are using a DC source, you might need to do something different for the back panel. In that case, we suggest using a panel-mount DC socket with flying leads back to the main PCB. For the flying leads at CON2 or CON6, consider soldering them to the underside of the PCB and feeding them up through the strain relief holes. We are now ready to close everything up. If you haven’t done so already, terminate the leads for the CON2 output and finalise your front panel to suit. Slide the assembly into the enclosure from the front and secure the front panel PCB with the four screws included with the enclosure. The main PCB should be flush with the back edge of the enclosure. Fig.7: it’s best to mark out your panels for drilling by lining them up with the PCBs. The hole for the USB-C socket is shown as rectangular, but you could make it by drilling out a row of round holes with a drill and then leave the corners rounded to match the rounded shape of the socket. Rest the insulating pad on top of Q1 and thread the 12mm-long M3 machine screw in from the outside. Flip the enclosure over so that everything stays in place. Add the thermistor, insulating washer, flat washer and fasten the nut to the screw to hold everything together. The metal tab of Q1 is connected to its collector (and also the POWER+ rail); this must be insulated from the screw and enclosure. You can check this with a multimeter set to measure ohms. Now attach the back panel using the remaining case screws and use the other 6mm-long machine screw to secure the PCB to the back panel. This will prevent the PCB from moving and flexing Q1’s leads when the USB cable is attached and detached. Finally, add rubber feet to prevent the Power Supply from sliding around and scratching your workbench. The PSU is now complete and ready for use. We have set the temperature setpoints to quite conservative values, so you could increase them if you feel comfortable doing so. The electronics can handle somewhat higher temperatures, but the case may get too hot to SC touch at higher levels. 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