Tolerance on +12v?

What is the supported range of obd2 socket voltage? I have to wire from scratch and would like to keep the “factory smoke” inside the microchips :slight_smile:

Also, is it sane to use the Photon’s v-in pin for a 600ma 5v draw when powered by the carloop obd2? It works via a front panel pc USB port through the photon, seems like a pretty polite load as long as the carloop is good with it.


I am not quite sure what you are asking about … using Carloop or Building a simulator, or attaching an extra peripheral to Carloop?

Carloop takes power from the 12V OBD2 port to power itself. Since automotive power is not clean at all, Carloop (hardware version 2.3) uses a RT8258GJ6 adjustable buck regulator to provide 5V to power the Carloop electronics up to 1.2A. There are also a few other components on the board to help protect itself.

There is also a CarloopXL (hardware version 3.x), which is not in production, that uses a NCP117 voltage regulator to provide 5V to power the Carloop electronics with enough capacity to power a microSD card (which take quite a bit of power).

In theory, CANbus is a differential signal which means you do not need the automotive 12V or Gnd as references for the CAN Hi and Low signals. Following that theory, you could power Carloop from another power source, but I have not tried it yet. If you are providing an alternate power supply or adding any extra peripherals, then you need to keep track of your power requirements. Remember, Carloop has to Power the Photon (or Electron or RedBearDuo), the CAN transceiver chip, a GPS if it is plugged in, plus anything else you might add. Also, keep in mind that the power supply circuitry is never going to be 100% efficient either.

Did I answer what you needed? If I missed your point, please clarify and I can try again.

Hi @cyclin_al1

Thanks for the detailed response! I’m just trying to understand if the carloop expects a regulated 12v or if it’s fine with typical dirty 9v(cranking)-15v (alternator, probably more like 14.6v) swings in a car electrical system. My demands for amperage are really low, I just don’t want to fry my carloop.

I’ll look into the datasheet for the regulator you mentioned later, thanks!


Carloop should be okay with power that is dirty like that. The Carloop expects automotive quality 12V at the OBD2 port. Like you say, automotive charging typically runs around 14.3V (or 14.6V is close enough), down to 11.4V when the car is not running and the battery is weak. It should be able to handle just fine transients of 17V or so, which are common in car electrical systems.

That’s great, thank you for confirming! I’ve never measured an OBD2 port to see its electrical characteristics. Carloop continues to impress, can’t wait for this project to be complete :slight_smile: