HFX – Electrical Test Set


Hui Gardens HFX electrical test set is the fusion of several basic electrical things that I’ve built while making other electronic things. It combines my HF1 – 100W Resistor Box, HF11 – 2 Wire RTD Simulator, the most useful parts of the HF2 -24V Variable DC Power Supply and more! I decommissioned the mentioned prototypes and repurposed almost all the parts including wires and resistors.

The Hui Gardens HFX features the following:

  • 24V adjustable DC power supply from 4x AA batteries (easy access) to loop power 4-20mA transmitters
  • 100W resistors including a 270Ω (close enough to a 250Ω resistor) for HART communication
  • 10 turn 2W potentiometers to allow for RTD simulation and 4-20mA simulation
  • 10W shunt to allow for high current measurement
  • Relay to take input and switch loads on and off and allow triggering of a frequency counter to test timing
  • 0.75″ spacing standard between banana jacks for double banana leads

I wanted something that can carry my Fluke 87V multimeter and be useful for things I test on a regular basis. I took a design cue from some of the high voltage equipment I see that allows for the meter and test leads to be stored in one case. Having a separate lead bag is really cumbersome and is prone to getting lost. I really like the brass wingnut chassis ground aesthetic. If it’s good enough for a 120kV hipot, it’s good enough for me!

Housed inside a Nanuk 920 hard case with a cut aluminum panel kit, the Hui Gardens HFX is pretty tough. The big red toggle switch cover is a must, the Chairman Mao emblem is an especially nice touch, but the best part is the custom 3d printed nameplate in brass.

HF2 – 24V Variable DC Power Supply


Hui Gardens HF2 24V variable DC power supply prototype is meant to power small electronics from hobby 3V3 and 5V sensors (e.g., Arduino and Raspberry Pi) to 24V industrial process 4-20mA transmitters. Housed in its own Pelican 1200 case, it can withstand rough transport and handling. It takes AC or DC input from an external source up to 30V AC/DC and outputs a rectified lower DC voltage. The input is a 2.1mm barrel jack that should be easy to find at an electronics parts store.

Due to the experimental intended purpose of this DC power supply, a 0.5A breaker is put in place instead of a fuse that requires replacement.

Hui Gardens HF2 features a 2W potentiometer for adjusting voltage output which should be plenty even when powering 4-20mA transmitters. Since it relies on setting of voltage via your multimeter prior to use, it is as accurate as your multimeter and there is nothing to calibrate.

The output comes via a binding post, so you can use banana plugs or bare wires. A standard spaced red and black post was chosen so that the fancy integrated two conductor leads can be used as well.

The red toggle switch cover and badge of Chairman Mao is the pièce de résistance taking this variable DC power supply to a new level.

Specification Value
Maximum Voltage Input 30V
Maximum Voltage Output 24V
Maximum Current 0.5A


This working prototype had been superceded by the Hui Gardens HFX electrical test set