Resistor in Constant current circuit


I am making some lighting for a project, using LEDs. There are going to be two sources of light:

  1. 13x 3W LEDs

  2. 2x 3W LEDs

I have acquired a LED-driver 0.7A with a minimum load of 25W and a maximum of 60W.

When connecting all 15 LEDs in series there is no problem. But, I would like to connect a Toggle Switch (ON-ON-ON) to give me three options.

a. Turn on all lights

b. Turn on only source 1

c. Turn on only source 2

Options (a-b) are no problem. Because they exceed the minimum load of the LED-driver. But option (c) does not.

To accommodate this I thought of placing a resistor in option (c), as shown in the circuit below. NB: I could not find the right switch, so only option (b-c) is illustrated. But it gets the point across.

I thought of using a 50W / 56 ohm Power Resistance. But I am not sure how to choose a resistance for a constant current circuit.

Any input will be appreciated!! :)

by madelaire
March 01, 2018

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