Originally posted by KLZE Porsche
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You could just use a diode and DC solid state relay to convert the AC waveform into a ground pulse signal. Many have a 3-32V DC input (wide enough to cover your VSS voltage) and tons of switching current, they are also fast enough to switch your device easily (by my calcs 200mph = 222.22hz).Supercharged - 94' PGT: ZE, MS2, W/M Injection, weight reduced, manual steering because weekend race car! mods and pics thread
Turbocharged - 06' WRX: 3" exh, ECUTEK ROM, MRT intercooler, VF34 pic
Nitrous Oxide - 79' Yamaha QT50 'Yamahopper' 70cc, MLM pipe, VM18 carb, dual stage reeds etc. pic
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Originally posted by stoker100 View PostYou could just use a diode and DC solid state relay to convert the AC waveform into a ground pulse signal. Many have a 3-32V DC input (wide enough to cover your VSS voltage) and tons of switching current, they are also fast enough to switch your device easily (by my calcs 200mph = 222.22hz).
Do you know if you can put DC across the switched AC terminals of a SSR? The signal being turned on and off by the relay is likely a 5VDC ref signal generated internally by the cluster since it is un-likely that it would be an AC ref.
---------- Post added at 12:18 PM ---------- Previous post was at 12:14 PM ----------
Originally posted by crazycanadian View PostWhat is it that you are working on?? Usually the PCM doesn't output a digital VSS signal for cruise control. Usually it comes from the ABS module or the Gauge cluster.Success is a measure of determination!
Bonneville Dreamer-(AKA Purple Pimp Mobile)
$500 Gas-Electric-Gas Reconversion/Restoration
Mini-me & 500k "Old Gal" RIP
Restoration of a legend
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Originally posted by KLZE Porsche View PostDo you know if you can put DC across the switched AC terminals of a SSR? The signal being turned on and off by the relay is likely a 5VDC ref signal generated internally by the cluster since it is un-likely that it would be an AC ref.Supercharged - 94' PGT: ZE, MS2, W/M Injection, weight reduced, manual steering because weekend race car! mods and pics thread
Turbocharged - 06' WRX: 3" exh, ECUTEK ROM, MRT intercooler, VF34 pic
Nitrous Oxide - 79' Yamaha QT50 'Yamahopper' 70cc, MLM pipe, VM18 carb, dual stage reeds etc. pic
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Originally posted by stoker100 View PostNot into the input of the SCR but into the output should be fine depending on the internal design, give me a part number and ill look it up. Something like a SY4090 should do the trick if your happy with a PCB mount component.
Damn I would hate to have to buy an Olds ECU and rig it up under the dash as a tach/speedo signal conditioner. That is a big-ass conditioner! Maybe I will post up some diagrams and whoever can look at them and see what is going on in the circuit and what is needed for the conversion wins!Last edited by KLZE Porsche; November 22, 2014, 07:32 AM.Success is a measure of determination!
Bonneville Dreamer-(AKA Purple Pimp Mobile)
$500 Gas-Electric-Gas Reconversion/Restoration
Mini-me & 500k "Old Gal" RIP
Restoration of a legend
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Originally posted by KLZE Porsche View PostActually -the more I look at the Olds diagrams -the more and more it looks to me that the ECU shunts the incoming VSS signal to ground and the cluster sees it as a voltage drop. I think I may have to buy an Olds VSS sender and hook it up/spin it to see what kind of output it has. This is too much for my brain and I think I am going to fry a diode or something.
Damn I would hate to have to buy an Olds ECU and rig it up under the dash as a tach/speedo signal conditioner. That is a big-ass conditioner! Maybe I will post up some diagrams and whoever can look at them and see what is going on in the circuit and what is needed for the conversion wins!
It is easy to convert the sine wave to a square wave.
The cheapest way is to build a simple circuit board using strip board.
If keeping cost down, this is the best way.
the idea of using a schmitt trigger is good, by using an op amp, by setting the differential input at a certain level by resistors, the output can feed into an opto darligton coupler NPN, with the emitter to ground.
This will give your isolated ground pulse.
Frequency in from your VSS will be the same frequency out.
You will have to first, find what frequency the VSS is giving out in relation to your vehicle speed.
If the VSS frequency is higher than the 4000 pulses/mile, then you can use a 4017 decade counter in-between the trigger op-amp and the opto-coupler to give you scaling, with selecting any one of the 1-10 outputs to feed the opto-coupler (and reset on the 4017) and the trigger op-amp output to the clock input of the 4017.
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Originally posted by KLZE Porsche View PostI am in the middle of another digital dash conversion and I have run into a problem with a speedo VSS incompatibility. I have a digital dash that requires 4000 pulses per mile of ground/no ground. The car vss sender is a powered one that outputs a sine signal of unknown amplitude.
How can I make a simple circuit that will turn this sine signal into a ground pulse signal? The pulses per mile are an exact match -so all I have to do is to convert the signal. Since I do not know the exact sine signal output amplitude -it would be nice to have a circuit that doesn't really care if it is 5v or 12v sine.
Please help me with this simple signal converter. Thanks!
Sorry, I didn't read this bit.
Just an op-amp with the -ve input between 2 resistors or pot to give your threshold voltage and + ve input to the VSS.
the output to drive a darlington NPN transistor via a resistor (emitter to ground, and possibly a 10K resistor from collector to +ve supply)
The collector terminal to your dash.
This will give your square wave ground pulse.
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