Cruise control with manual transmission

[nic55kel]

I am in the process of changing out a C6 transmission for a 4 speed.

I know that I will have to have a clutch switch to disengage the cruise but I had a different thought on this.

Does anyone know approximately how many pulses per mile the factory cruise control operates at?

My thought was to use the engine as the signal source (tach signal) which with 3.55 gears and a 300 six would come out to about 7000 ppm. Just wondering if this would be anywhere near to or a near multiple of the factory signal.

I like the idea of the CC directly controlling engine speed and thus no chance of engine runaway with the clutch disengaged or the transmission in neutral.

Just thinking

Bob

[kramttocs]

Do you mean the engine directly controlling the speed control (as opposed to the tranny/od)?

In my digging a few months ago, 8k is what I found but that wasn't directly from any Ford doc.

Can you explain more of your plan?

Are you using a vss for the GVOD or is it manually controlled?

[Gary Lewis]

I can't tell you how many pulses per mile the speed sensor puts out, but I can say that the target speed for the speedometer cable is 1000 RPM at 60 MPH. Hope that helps.

And please keep us apprised of your results.

[nic55kel]

I can't tell you how many pulses per mile the speed sensor puts out, but I can say that the target speed for the speedometer cable is 1000 RPM at 60 MPH. Hope that helps.

And please keep us apprised of your results.

I think 8k ppm is correct which means I can use the tach signal for the cruise control.

Yes the intent is to use the ignition system as the reference for the cruise control.

I am sure there will be a bit of waveform processing required but that should be relatively minor, the important thing is that the frequency is in the correct range.

I think it would be neat to have cruise control in all 4 gears hopefully it works out.

The GVOD will be gone along with the C6 so no concern there.

We are in the middle of a snowfall warning here with about 8" already on the ground so not much happening for the next week or so.

Bob

[Gary Lewis]

I think 8k ppm is correct which means I can use the tach signal for the cruise control.

Yes the intent is to use the ignition system as the reference for the cruise control.

I am sure there will be a bit of waveform processing required but that should be relatively minor, the important thing is that the frequency is in the correct range.

I think it would be neat to have cruise control in all 4 gears hopefully it works out.

The GVOD will be gone along with the C6 so no concern there.

We are in the middle of a snowfall warning here with about 8" already on the ground so not much happening for the next week or so.

Bob

Yes, you will need to do a LOT of waveform processing. The Vehicle Speed Sensor signal is basically a square wave, but the tach signal is UGLY! Huge spikes as the magnetic field collapses in the coil, and you have to isolate that with a resistor and then process it. I'll be anxious to see how you do that.

However, I'd think about a 555 timer as it could easily provide the square wave and be triggered with the tach signal.

[kramttocs]

Yes, you will need to do a LOT of waveform processing. The Vehicle Speed Sensor signal is basically a square wave, but the tach signal is UGLY! Huge spikes as the magnetic field collapses in the coil, and you have to isolate that with a resistor and then process it. I'll be anxious to see how you do that.

However, I'd think about a 555 timer as it could easily provide the square wave and be triggered with the tach signal.

So this would be more of a "set engine RPM" control that can be used as speed control

Intrigued by how you go about it also.

[Gary Lewis]

So this would be more of a "set engine RPM" control that can be used as speed control

Intrigued by how you go about it also.

If it would help I can put a VSS on my lathe and figure out what the pulse rate per revolution is. And even take a pic of the waveform.

[nic55kel]

If it would help I can put a VSS on my lathe and figure out what the pulse rate per revolution is. And even take a pic of the waveform.

I am pretty sure that the vss signal will be close to a sine wave, basically it is just a little ac generator.

I would be more interested in the waveform of the tach signal.

I got this off the internet for a points and coil system which should be fairly similar:

If one just took the coil current waveform it would be easy to get that into a square wave.

Regarding frequency of the signal - it makes sense to me that the engineers designing cruise controls back in the day would have used a readily available signal as a speed reference, the obvious source being the ignition system. This tends to make me think that 8000 ppm is correct and online research confirms that.

Yes it would be using the cruise control to directly control the engine speed. I think if one tried it in say neutral the rpm would hunt badly as I am sure the units response is relatively slow and it would overshoot the corrections badly. As a vehicle speed control on a vehicle with manual transmission it should behave exactly the same as if monitoring the vss signal.

It is going to be a little while before I get to try it out but it looks promising.

Bob

[Gary Lewis]

I am pretty sure that the vss signal will be close to a sine wave, basically it is just a little ac generator.

I would be more interested in the waveform of the tach signal.

I got this off the internet for a points and coil system which should be fairly similar:

If one just took the coil current waveform it would be easy to get that into a square wave.

Regarding frequency of the signal - it makes sense to me that the engineers designing cruise controls back in the day would have used a readily available signal as a speed reference, the obvious source being the ignition system. This tends to make me think that 8000 ppm is correct and online research confirms that.

Yes it would be using the cruise control to directly control the engine speed. I think if one tried it in say neutral the rpm would hunt badly as I am sure the units response is relatively slow and it would overshoot the corrections badly. As a vehicle speed control on a vehicle with manual transmission it should behave exactly the same as if monitoring the vss signal.

It is going to be a little while before I get to try it out but it looks promising.

Bob

Check out my post back on FTE which has a tach signal on my scope. Perhaps that is what you need?

As I think about it, I could put in a toggle switch in to determine whether the speed control gets a feed from the VSS or tach.

[nic55kel]

Check out my post back on FTE which has a tach signal on my scope. Perhaps that is what you need?

As I think about it, I could put in a toggle switch in to determine whether the speed control gets a feed from the VSS or tach. http://www.garysgaragemahal.com/uploads/6/5/8/7/65879365/thinking-26_orig.jpg

Gary thanks for that information, I see that your scope trace agrees pretty well with the waveform I had found.

I would not connect a raw tach signal to the cruise module - too much chance of the smoke escaping.

I would be interested in the wave form at the coil +ve terminal as I think it would be a much cleaner approximation of a square wave.

Now that makes me think of a really simple possible solution to getting the signal:

Even better it would be an isolated signal.

I would start with a 10t primary and 50 t secondary with maybe a small capacitor across it to bleed off any ringing and take it from there.

Just getting this on file now for when I get to play with it in summer.

Bob