928sg Posted June 17, 2023 Report Share Posted June 17, 2023 this is what I have spec'd out for the tach output. Clusters are expensive and hard to find so I don't want to cook it. Quote Link to comment Share on other sites More sharing options...
928sg Posted September 2, 2023 Author Report Share Posted September 2, 2023 ended up buying a scope and playing around with it. This was taken from a stock car @ 2K RPM. Looks to be a 6 volt output. how do I configure the tach output to get relatively close to this? I realize I can dial it in after it is running but as I stated above clusters are expensive so I'd rather come in on the low side than the high side. Quote Link to comment Share on other sites More sharing options...
Adamw Posted September 3, 2023 Report Share Posted September 3, 2023 A tacho is a frequency driven device, it doesnt care about voltage, as long as the voltage goes above and below its thresholds to be considered an edge it will work. An ecu aux output has a 12V pull-up so it will give a 0-12V square wave. Quote Link to comment Share on other sites More sharing options...
928sg Posted September 3, 2023 Author Report Share Posted September 3, 2023 the 6 volt signal was consistent and the square wave was wider and slower at idle vs 2K shown here. My concern is overdriving the tach while I'm trying to get it dialed in. The tach is part of an integrated cluster and new one is 6K USD. Does multiplier correlate to voltage or frequency? Does duty cycle correlate to voltage or frequency? Quote Link to comment Share on other sites More sharing options...
essb00 Posted September 3, 2023 Report Share Posted September 3, 2023 Multiplier correlate to frequency Duty cycle correlate to voltage RMS value. Quote Link to comment Share on other sites More sharing options...
928sg Posted September 3, 2023 Author Report Share Posted September 3, 2023 37 minutes ago, essb00 said: Multiplier correlate to frequency Duty cycle correlate to voltage RMS value. Thanks~! This was what I was looking for. Quote Link to comment Share on other sites More sharing options...
DerekAE86 Posted September 3, 2023 Report Share Posted September 3, 2023 2 hours ago, 928sg said: Thanks~! This was what I was looking for. Changing the duty cycle wont change the peak voltage though. The ECU will still be putting out 12v when in the "on" state. Not that it matters because the picture of your scope readout is actually showing a 50% duty cycle 12v signal. It says down the bottom that it's 5v per division. The waveform spans just over 2 divisions. And it's "on" for 50% of the time and "off" for 50% of the time = 50% duty cycle. The reason why the DC voltage reading is showing 6.27v is because 50% of the time its 12v and 50% of the time its 0v. Which means the average reading is 6v. 928sg 1 Quote Link to comment Share on other sites More sharing options...
928sg Posted September 9, 2023 Author Report Share Posted September 9, 2023 Thanks for the explanation. I had no clue how to read this. Quote Link to comment Share on other sites More sharing options...
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