Question for electronics GURUS

[KLZE Porsche]

I 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!

[BLUEnoEQ]

Are you saying you have a sinus wave and need a square wave, or vice versa? But the pulse rate is already the correct hertz.

[BLUEnoEQ]

How about a Dakota digital universal signal converter? You'll have to see if that suits your needs or not, but it's made for that sort of conversion. $80 on the nets

[KLZE Porsche]

How about a Dakota digital universal signal converter? You'll have to see if that suits your needs or not, but it's made for that sort of conversion. $80 on the nets

I already have one of those -but it will not convert a sine voltage to a pulse ground. Yes the frequency is exact at 4000 pulses per mile.

Since the cluster is looking for 4000 ground pulses per mile (similar to what you would get with a reed switch type sender -if I were to connect a sine wave type signal (voltage pulse) this could possibly fry the cluster. So I would like to convert the sine wave type pulse to a grounded pulse. This would require a simple circuit so that when it detects a sine voltage of positive voltage -it outputs a ground through an isolated ground circuit.

I am guessing that the sine voltage will need to be clipped because I believe one pulse with a sine wave type signal is considered to be both the negative and positive side of the sine.

I could probably figure this out eventually on my own -but I was hoping for a short cut that some electronics guru might have with a simple existing circuit or IC that is easily wired up.

The Dakota works with Sine type senders (most common type) and can convert one number of pulses to another or sine voltage to pulse voltage -but I do not believe it will convert it into a ground pulse (on/off).

[BLUEnoEQ]

So you need an analog to digital converter. With very specific needs. How about trying a simple 555 timer circuit set for 1:1. It's a very basic ic available at radio shack. Schematics are everywhere online for ways to use them.

[KLZE Porsche]

So you need an analog to digital converter. With very specific needs. How about trying a simple 555 timer circuit set for 1:1. It's a very basic ic available at radio shack. Schematics are everywhere online for ways to use them.

Yea -I know -I have a bunch of 555's here -but I was hoping for something a little more tailored. I will look into it if nobody comes up with something else. I find it hard to believe that there isn't something already out there to do this. I know I am not the only one that loves to splice this cluster into that and so on.

[BLUEnoEQ]

Start thinking of cars that had digital dashes as factory options and search. Cavaliers and Camaros had them. I think the vettes only had the digital dash so no home engineering there. No joke... Look for a Knightrider kitt site that sells parts.

[KLZE Porsche]

Start thinking of cars that had digital dashes as factory options and search. Cavaliers and Camaros had them. I think the vettes only had the digital dash so no home engineering there. No joke... Look for a Knightrider kitt site that sells parts.

I know all of this already. I am simply looking for an existing circuit that has been used for a very simlilar setup.

All I need to do is to take a sine input of a given frequency and turn it into an on/off signal. I don't need it to be a picky circuit -but just one that sees the positive side of the sine wave and creates a pulse for every positive peak it sees. I can always use the digital pulse output to drive a switching transistor to provide the pulsed ground.

Since the PPM's are exact for both units -the cluster conversion should be fairly straight forward.

[BLUEnoEQ]

If it only needs the positive pulse then you need a half wave rectifier. If you need the negative ac pulse to create a positive pulse also, then you need a dual polarity full wave center tap rectifier. The first type is basically just 1 diode and will give you 2000 + pulses, skipping the negative half of the wave. The other has 4 diodes and will give you 4000 + pulses for 2000 + and 2000 -. I doubt there is anything off the shelf that will work for your specific situation.

[KLZE Porsche]

If it only needs the positive pulse then you need a half wave rectifier. If you need the negative ac pulse to create a positive pulse also, then you need a dual polarity full wave center tap rectifier. The first type is basically just 1 diode and will give you 2000 + pulses, skipping the negative half of the wave. The other has 4 diodes and will give you 4000 + pulses for 2000 + and 2000 -. I doubt there is anything off the shelf that will work for your specific situation.

I am going to use a Schmitt trigger.

[BLUEnoEQ]

Is that something you can use by itself or in combination with rectifier? Will it cause the gauge to read high until the opposite cycle, then low?

[KLZE Porsche]

Is that something you can use by itself or in combination with rectifier? Will it cause the gauge to read high until the opposite cycle, then low?

The Schmitt trigger will operate (on/off) at a given threshold. A single Zener will suffice to cut the bottom half of the sine. And thus a square wave for every full sine cycle.

I spent 20 years doing electronic stuff and so I always can go back to it if I want -but I am lazy and don't like doing electronic design as much as I enjoy mechanical design. So when possible -I try to let someone else solve it who likes the electronic side of things.

[BLUEnoEQ]

I probably enjoy it more than most. There are 2 apps for the phone. 1 is called Electrodroid and the other Everycircuit. The apps are linked and have all kinds of useful, no, vital information. Electrodroid has all the stuff that's hard to remember + calculators for anything, pinouts for most home audio and video wires. Everycircuit, you can build a circuit and see how it works right there, say in radioshack looking at what you need to build it for real. It actually has a working half wave and full wave rectifier design, all you have to do is input the numbers you're working with.

[crazycanadian]

Mx3, Mx6 gauge clusters all convert the speed sensor sign wave into a digital signal out put for your cruise control modules.. butcher a cluster for just that part of it?

[KLZE Porsche]

Mx3, Mx6 gauge clusters all convert the speed sensor sign wave into a digital signal out put for your cruise control modules.. butcher a cluster for just that part of it?

Good idea that I hadn't thought about. Most cars use PCM for the cruise that is derrived from the sine out-put of the VSS. Good thinking because I will bet that there is a PCM output on this car from the ECU to the cruise control.