Turning a 12V 25mA signal into a ground input signal???

I'm a mechanic and don't know that much about electronics. We are currently building a car with a Dakota digital dash which looks for a ground from the brake proportioning valve or the master cylinder fluid level switch to turn on the brake warning light. We are also installing an aftermarket electric E-brake in the car and the control module for it puts out a 12v 25mA signal (+) that's meant to turn on an LED for when the E-brake is on. We are looking for a way to use that 12V 25mA + and turn it into a ground input to the Dakota digital control module so that it would turn on the same Brake warning light. I was thinking it could be done with a NPN transistor but I'm not sure how to build the circuit. It would need some resistors to work without frying right? What resistor values should I use? Correct me if I'm wrong but 12V @ 25mA would probably not be enough to switch on a common automotive relay would it?? (command coil is usually 80-100 ohms). I'm sure this would be a fairly easy circuit for someone that has a better understanding of electronics than I do. Any help would be greatly appreciated. Thanks!

by MrGearHead
November 03, 2019
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.