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Help with building your Speeduino, installing it, getting it to run etc.
By Vivaboy
Hi all,

I'm having some issues with my speeduino 0.4.3 board loosing sync after 550rpm. I have been simulating the crank input on the bench using a mega, using 36-1 crank (and jump leads), and have a vr conditioner set up on the board. The issue percists no matter where I take the ground from (even if I remove the ground), just consistantly loosing sync at the same rpm. It's as if the signal is weak, as I can wave my phone next to it and it looses sync. Ive tried tracing back the connections for any dodgy solder joints but cant find any.

Any help would be greatly appreciated, I've been pulling my hair out over the past few weeks trying to find the source of this.

Do you have resistor type spark plugs?


Are you still on the bench?

Remove the vr conditioner, and do not add a pull up jumper? set to hall

What do you get then?
By Vivaboy
Thanks for the reply, I am still on the bench.

Trying that gives me nothing, it doesnt crank at all. Interestingly whenever I touch the vr conditioner it stops cranking, as if there is a loose connection there?
By NickZ
normally it should be ok, but the output from another mega isn't really the right signal for a VR conditioner.
Id say the signal isn't really connected and its picking up the noise, Ive had this happen before.

On my bench test rig, i don't have the VR- wire connected at all.

id remove the VR conditioner and try will HALL settings first.
By Vivaboy
Thanks all,

I think that might be the case NickZ, i cant seem to get anything when connecting to hall.
Ill have a bit of a play around with it. I might set up the trigger wheel on the bench to test it out, or maybe fit it to the car and test it that way (the car's running on points at the minute).

Thanks for your help,
User avatar
Note that some VR conditioner circuits and chips do not like signals that don't go close enough or below a minimum or negative threshold. The MAX chips and LM1815 are examples that can be fidgety about this. If your installed input will be a VR, you can output your test square-wave signal through an audio transformer in order to provide a true (+) and (-) voltage signal to Speeduino.


It's not pretty, but it gets the job done :lol:. I used a 600:600 (1:1 with good resistance) transformer inline of the raw Ardu-Stim signal to get this :
Ardu-Stim+TxFormer Scope.png
Ardu-Stim+TxFormer Scope.png (5.42 KiB) Viewed 373 times

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