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
Add comment...

Please sign in or create an account to comment.

No Answers

No answers yet. Contribute your answer below!

Your Answer

You must log in or create an account (free!) to answer a question.

Log in Create an account

Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

Search Questions & Answers

Ask a Question

Anyone can ask a question.

Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.

About This Site

CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.

We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.

Acceptable Questions:

  • Concept or theory questions
  • Practical engineering questions
  • “Homework” questions
  • Software/hardware intersection
  • Best practices
  • Design choices & component selection
  • Troubleshooting

Unacceptable Questions:

  • Non-English language content
  • Non-question discussion
  • Non-electronics questions
  • Vendor-specific topics
  • Pure software questions
  • CircuitLab software support

Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.