# How to test the output current of a LED driver without a LED lamp?

I have very basic knowledge of electronics but I have to design a circuit to control this LED driver (Constant Voltage + Constant Current LED Driver).

I already have a prototype and I need to test it, but I do not have a 20V LED lamp of 40W to check that the control is done correctly. That is, the output current is controlled by PWM or by 1-10V.

Instead of using the LED lamp as a load, could a 10-ohm 25W resistor be used? Or, is it enough to connect the ammeter directly to the output of the LED driver? Thank you.

• 10 ohm 40 W resistor? A ~60 W 24 V light bulb? Two ~30W 12 V light bulbs in series? A 40 W 20 V zener diode? Commented Jan 31, 2018 at 8:49
• Pay close attention to specs! That resistor is 10mΩ, not 10Ω. Connecting it to the driver will have the same effect as a short. Commented Jan 31, 2018 at 9:02
• @DmitryGrigoryev, Yes thanks. I got confused when looking for the component to write the link. Commented Jan 31, 2018 at 9:04

An ammeter will need a load in order to measure the current flowing through the circuit. The Ammeter alone will not suffice.

Instead of using the LED lamp as a load, could a 10-ohm 25W resistor be used?

Seeing as you want a 40W load, then no, this will not do. You would need a resistor that can take the 40W.

If you want to simulate a 40W load, then start again from the beginning. Ohms law is your friend here. Find the resistor you require, and just make sure you have one that can take the current/power.

R = V/I

P = I^2*R or V^2/R or I*V

Use those equations to find a resistor you want to use, work out the maximum power it would be handling, then find a component to match your answers. Fit the component as a dummy load, then connect your ammeter in series with the circuit to measure the current.

Or, to make it much easier on yourself, just get yourself the 40W LED bulb you require...... they are pretty common.