Aces rpm pick up

[CtrMint]

Morning All,

I've finally picked up my data logging project I started with John and James, and hope to finish it this time.  My new found interest is driven by the discovery of some suitable hardware on which to productionise the build, something that was previously an issue.  If all goes to plan, the solution should cost around £30 in parts!  Plus require zero setup!

Before I tackle the logger, I'm going to do a dry run, using the same hardware on an easier project, well in theory!  Replacing the ACES rpm shift monitor.  
 

Documentation on how the ACES system picks up RPM is thin on the ground, does anyone know where I might find how it works, and the operating spec.

Thanks

 

 

[Jonathan Kay]

"Documentation on how the ACES system picks up RPM is thin on the ground, does anyone know where I might find how it works, and the operating spec."

Have you got everything that I assembled here?

Jonathan

[CtrMint]

Hi Jonathan, yes I've seen the thread and the manuals, but I want to get into the real detail, I guess of the black and white connection.  My knowledge of the automotive side is pretty thin.

[Jonathan Kay]

If you can't find any more specification how about using a high-impedance oscilloscope to have a look at the voltage on the signal wire while it's working as is?

What's the engine and ECU?

Jonathan

[CtrMint]

I'm trying to build with the equipment I have, sadly that doesn't include a scope.  I'm also concerned about peaks and noise that might occur on the signal line.

Your comment however re which engine made me think, (420R btw) Maybe there is a simpler solution which avoids the various ecus and engines.

[aerobod - near CYYC]

Hi Mark, the ACES feed should be off the white/black wire that connects between Pin 34 on the ECU and the back of the Tacho (unless it is the Stack dash that has an input from the ECU and an output for the shift lights).

The signal should be a square pulse, but there are some output config options on the ECU. My non-Caterham 9A4 ECU Pin 34 output is set to 4 pulses per cycle and 75% duty cycle (the percentage of time the signal stays at 12V), with both the ACES control unit and Tacho set to match the number of pulses.

[CtrMint]

Awesome James and thanks. I think a simple opto-coupler solution will work, isolating and dropping the signal down to 3v.  I can then feed my microcontroller from the signal knowing I won't spike the input.

Though I'm currently back in the weeds of our original venture, currently questioning some of our conclusions.  I'm trying to make sense of that infamous missing flow control.  I may have found a different high level protocol SAE J1939 (BAM) using classic can which explains the missing flow control. Though I'm might be completely wrong, I've got my head in the books again.