The device was sent to me by RD Official Store in Aliexpress for review.
Here's the product's page: RD LD25 25W Electronic Load
Manufacturer Specifications
Rated Voltage: DC4-25.0V
Rated Current: 0.25-4.00A
Constant Current Resolution: ±（1％+3 digits）
Working Temperature: -10℃-40℃
Fan Speed: 5800±10%RPM
Expansion ports：Micro USB, Type-C
Product size: 83.8x41.1x27.9mm
Product weight: 56.51g
Thanks to the exposed wires and traces, the device has an industrial look.
The top part of the device includes the input ports, the heatsink assembly and the controls.
The back side utilizes 4 plastic feet to elevate the pcb and prevent any accidental shorts.
The two big components seen is a Texas Instruments LM317 Regulator and a TIP 122 NPN Transistor (rated for up to 5A).
As seen, the transistor is mounted directly onto the heatsink with some thermal paste.
The input side of the electronic load is consisted out of a USB 2.0 port, a micro-USB port and a type-C port.
According to the manufacturer, the recommended max current for the micro-USB port is 2A and 4A for the other two ports, though there isn't an auto cutoff.
The control side contains the 4 digit LED display, two tactile buttons and a multi-turn potentiometer used for adjusting the current.
You can also seen the aluminum heatsink with the thermally-controlled cooling fan mounted on top of it.
User Interface
The operation of the device is super simple.
Here's how a regular use scenario looks like:
1. Plug in the input.
2. The display will start blinking while displaying the selected current draw.
3. By rotating the potentiometer the load is adjusted to the desired level.
4. Pressing the on/off switch makes the display stop blinking which indicates that the load is now being applied to the input.
5. The on/off switch can be pressed at any time to stop the device from drawing current.
Using the 'SET' button, the user can switch between the three available readings.
Volts - Current - Power
A constant press over the on/off button will make the display show an 'ON' or 'OFF' notification.
The ON condition means that the load will automatically start drawing current once an input is connected, which practically bypasses the blinking screen that was described in the previous usage scenario
and thus prevents the user from previewing the selected load.
Such setting can be useful in case the electronic load is used for mass testing the performance of chargers.
Overall the LD25 is a great gadget to have in your arsenal for testing your psu's performance in a glance.
