After the acquisition of my Power Designs 5015D power supply, I really wanted to upgrade the display module so that I had an extra digit of resolution. I already had a few ADC/LED meter boards left over from previous projects, but needed a display board to pair with it.

While the original “OTE 2020” display boards worked fine with the new ADC/LED Rev. 2.0 driver boards, I wanted to update the design to utilize the specific footprint for the display modules, and increase the trace widths to better match the driver board.

The Lumex Opto LDS-C416RI 7 segment LED displays use a standard 14 pin DIP layout, but only utilize 10 pins. Using the 10 pin footprint allows for easier routing of traces, and the ability to use bigger circuit traces. I also slightly raised the height of the LED’s to better utilize the front panel display opening and viewing angle.

After pairing up the display and driver board, it was time to tackle modifying the 5015D from a 200 mV display output to a 2.00 Volt full scale output. I used the schematic for the TW5005D power supply as a starting point, as it has a similar layout and meter circuit compared to the 5015D.

The output of the Volts and Current metering circuits are comprised of a simple voltage divider with a trimmer resistor for calibration. By changing one resistor in each divider circuit the output can be changed by a factor of 10 to increase the ratio to 2.00 volts full scale.

While I was making changes to the circuit, I also changed out both of the trimmer potentiometers to a Bourns 3299Y‑1–101LF 100 Ohm 0.5W PC pin 25 turn units. This allows for a finer adjustment than the original single turn trimmers. R43 in the current circuit was changed from a 15 Ohm to a 158 Ohm 1% resistor. R11 in the voltage circuit was changed from a 174 Ohm to a 1.7K Ohm 0.1% resistor CMF551K7000BHR6.
Calibration was fairly straightforward, by setting the output voltage to 50 volts with a calibrated voltmeter connected and adjusting R10 V CAL trimmer until the meter matches the external voltmeter. For current calibration I connected a calibrated DC amp meter capable of at least 3 Amps, and an 8 Ohm 50 watt load resistor and set the output for a 1.5 amp reading on the external amp meter. I then adjusted R14 I CAL trimmer until the front panel meter matched the external amp meter.
Warning, do not leave the current output at 1.5 Amps for very long as the resistor will be dissipating 18 watts and will heat up quickly.

My collection of Power Design supplies has grown over the past few years, but I still use most of them. Probably the least used is the 6150 as I infrequently need that much power for most of my projects.

Eagle CAD V7.7 board and schematic ZIP file for Rev. 2.4 meter display board
Eagle CAD V7.7 board and schematic ZIP file for Rev. 2.2 ADC/LED driver board