DIY bench test equipment / 2026-09-17

Building a Basic Bench Power Supply: LM2596 + DSN-VC288 + a Manual Pot

I've been slowly working towards a full modular test bench — an oscilloscope, signal generator, VNA, and programmable power supply, each one a standalone PCB module in its own enclosure, all controlled from one PC program. Before jumping into digital control loops and firmware, I wanted a basic, manual, uncontrolled version working first — just to prove out the power path, the parts, and the mechanical layout with my hands on a knob. Here's the first working step: a simple adjustable DC bench supply built from three cheap, widely available parts.

The parts

• LM2596 adjustable buck converter module — the core regulator. These come with an onboard trimpot for adjusting output voltage.


• DSN-VC288 digital panel meter — a combined voltmeter/ammeter display module. This is a pure measurement display (no microcontroller, no digital output) that reads voltage via its VT pin and current via an external shunt resistor, and shows both on tiny 7-segment LEDs.

Why start manual
It's tempting to jump straight to a microcontroller-driven, digitally-set voltage with readback and logging. But there's real value in proving the basics first: does the buck regulator behave cleanly, does the display track reality, is the mechanical layout (knob, jacks, wiring) sound? Answering those questions with a multimeter and a knob is a lot faster than debugging them through a firmware layer at the same time.
This manual build becomes the foundation — the next version replaces the trimpot with a digital potentiometer (ex. DS3502) and adds an INA226 for digital voltage/current readback into an ESP32, closing a real setpoint control loop. But that's a separate post.

Swapping in the external pot
With the board unpowered, I checked the stock trimpot's wiring with a multimeter to confirm which legs were actually in circuit. Then desoldered the onboard trimpot. Ran three twisted-pair leads from the vacated pads out to the external 10kΩ pot's three lugs (outer, wiper, outer) — keeping the leads short and twisted to reduce noise pickup, since this node sits directly in the regulator's feedback path.
Mounted the pot through the enclosure panel using the kit's washer and nut, and pressed on a knob cap.

Wiring in the DSN-VC288 display
The DSN-VC288 is a drop-in fit for exactly this kind of manual build — it needs no digital interface at all: VT pin ties to the output voltage rail being measured. A shunt resistor sits in the current return path, feeding the current-sense inputs.
V_ADJ and I_ADJ trimpots on the display board calibrate the voltage and current readings against a known reference (I checked both against a multimeter and adjusted until they matched).
I_ADJ_Z zeroes the current reading with no load applied.

Power in
DC power comes from an AC-to-DC adapter I already had, feeding the LM2596's input. No mains wiring anywhere in the enclosure itself — the AC/DC conversion happens entirely in the external brick, which keeps the build simple and avoids any mains safety concerns inside the enclosure.

Result
Turning the knob sweeps the output voltage, and the DSN-VC288 gives a live, accurate voltage and current readout with zero digital components involved. It's a genuinely useful little manual bench supply on its own, and now serves as the tested, trusted analog foundation for the digitally-controlled version I'm building next.

What's next
The next phase replaces the manual pot with a digital potentiometer and adds an INA226 for digital readback, driven by an ESP32 running a closed control loop. That module will eventually plug into a larger test bench stack — oscilloscope, signal generator, and VNA modules alongside it — all readable from one PC program, with a separate lightweight "supervisor" microcontroller silently polling every module in the background for temperature, dissipation, and error codes.

More on that build soon!!!