Why a Dedicated Power Supply Matters
USB chargers and phone adapters work for some tasks, but they share a critical flaw: no current limiting and no voltage readout. When you short a circuit or draw too much current, a USB charger either shuts down abruptly or, worse, catches fire. A bench supply with current limiting tells you exactly what happened and protects your circuit from damage. Voltage readout means you catch the 3.3V vs 5V mistake before it fries your sensor.
For anyone working with motors, LEDs, multiple logic rails, or anything beyond basic Arduino projects, a bench supply is not optional — it's the foundation of a functional bench.
What We Tested
Five units covering the practical price range: the Hanmatek HM305 (~$35), RD Tech DP3005 (~$65), Korad KA3005P (~$90), Tenma 72-2975 (~$110), and the BK Precision 1685B (~$180). Each was tested with a precision multimeter, an electronic load, and a 100MHz oscilloscope to measure ripple under load.
Voltage Accuracy and Readout
All five units specify ±0.1% voltage accuracy, which is broadly accurate but masks real-world variation. We measured output voltage with a Keysight 34461A 6.5-digit meter across 3.3V, 5V, 9V, 12V, and 24V rails.
Best accuracy: BK Precision 1685B. Within ±0.02% at all test voltages. The readout matched the meter within one count. Professional-grade calibration.
Acceptable accuracy: Korad KA3005P and Tenma 72-2975. Within ±0.05%. Fine for any maker-level work. Small errors are correctable by adjusting the set point.
Worst accuracy: Hanmatek HM305. Consistent +3% error at 3.3V — delivering 3.40V instead. Not a problem if you check with a meter, but the display readout will lie to you consistently.
Current Limiting: The Feature That Saves Circuits
Current limiting is the single most important feature on any bench supply. When set correctly, it prevents a dead short from destroying a component. It also lets you test LED current without smoking the LED, and run motors at stall current without burning out the driver.
We tested current limiting precision by drawing increasing current from each supply until the current limit engaged, measuring the trip point against the set value.
Most precise current limit: BK Precision 1685B. Trip point within 1% of set value. Smooth transition into constant-current mode — no overshoot.
Acceptable: RD Tech DP3005. Within 5% of set value. Occasional 10% overshoot on initial trip. Correctable with a small adjustment.
Not reliable: Hanmatek HM305. Current limit would occasionally not engage until 15% above set value. For protecting circuits, that's not good enough.
Ripple and Noise Under Load
Ripple matters for sensitive analog circuits, RF projects, and audio work. We measured output noise with a 100MHz oscilloscope under 50% load conditions using a 10:1 probe with a ground spring.
Cleanest output: BK Precision 1685B. Ripple below 1mV RMS under all test conditions. Silent in every sense — the fan is barely audible.
Good for most work: Korad KA3005P. Ripple around 2-3mV RMS. Fine for digital logic, microcontrollers, motors, and most sensor work.
Noticeable: Hanmatek HM305. Ripple of 8-12mV RMS — high enough to cause issues with sensitive analog front ends or low-noise sensor circuits. Fine for digital work; avoid for anything RF or precision analog.
Power Delivery: 30W vs 60W vs 100W
Wattage determines what you can run. The practical limits:
- 30W (5V @ 3A): Arduino projects, small LED arrays, Raspberry Pi, single-board computers. Not enough for motors or anything with inductive load. Sufficient for ~70% of typical maker bench tasks.
- 60W (12V @ 5A or 24V @ 2.5A): The practical sweet spot. Runs NEMA 17 stepper motors, 12V LED strips, small CNC spindles, and laptop USB-C PD-triggered projects. Covers ~90% of maker bench needs.
- 100W (24V @ 4A): NEMA 23 motors, higher-power LED work, benchtop CNC machines, and anything with a meaningful heating element. Overkill for most electronics; necessary for physical making.
Form Factor and Daily Use
The Hanmatek HM305 and RD Tech DP3005 are compact (half-rack width) — good if bench space is tight. The Korad, Tenma, and BK Precision units are full-width bench units with built-in handles and better cooling for sustained use.
All five have USB charging output on the front panel, which is genuinely useful for charging devices without dedicating a power supply. The RD Tech DP3005 and Korad units have programmable memory — save three preset voltages and currents for your most common setups. Worth the premium if you switch between projects frequently.
Verdict
Best value: RD Tech DP3005 at $65. 30W is limiting for some maker work, but 5V @ 3A covers most projects. The programmable presets, decent accuracy, and reliable current limiting make it the right choice for anyone building their first serious bench without spending $150+.
Best for serious makers: Korad KA3005P at $90 (or Tenma 72-2975, which is the same unit rebranded). 60W handles motors, LEDs, and SBC projects comfortably. The 2-3mV ripple is low enough for most analog work. Buy once.
Best for precision/RF: BK Precision 1685B at $180. If you're working with sensitive analog circuits, RF, or anything where 1mV ripple matters, this is the unit. For pure digital maker work, it's overkill — but if you need it, you know why.
Skip: Hanmatek HM305. The voltage inaccuracy, unreliable current limiting, and high ripple make it suitable only for the most basic LED testing. The $30 savings aren't worth the compromises when the Korad is only $25 more.