DIYEFI.org Forum

Should we use a simple Hall input for this first round here? If so this part of the schematic is easy, three wires, on is the hall output going to the ECU.

My preference would be to keep the VR signals as short as possible to keep the antenna's minimal. Then run a hall like signal to the ECU. So I really don't think we want the VR in this part of the design.

When doing a hall, I know the sensors I have are 12V compliant. Are the typical automotive hall's the same? Or do they sometimes require current or voltage conditioning?

I'm not sure, but I think you will find that everyone wants their VR stuff on board. LM1815 is the way forward for that IMO.

We want two inputs to the cpu for this, either of which or both can come through the LM1815s or not. that way a user can have an opto and a hall, an opto and vr, a vr and hall or two of any of them. If not required for a hall/opto user the lm chips can be left out.

I was picturing the VR could spike back, but I really don't know much about the LM1815. I'm still reading / re-reading the data-sheet. That is why I was picturing the opto. I figured it we put in an opto, then why not put it close to the MCU, so protect both. Probably not required for either, also we have the digi-protect circuit, so that probably takes care of those spikes anyhow.

I'll put the VR kind of in parallel with the hall input.

I think you should use the same trace coming in. That way the instructions are the same and no pins are wasted. If it's a VR signal you put the chip in. If it's a Hall signal you don't and just install a jumper from vrin pin to square out pin. Up to you though I guess.

That's exactly what I meant by in parallel. So we're on the same page here.