Any Electronic Gurus Out There?

[Steve83]

I hope this makes sense...I'm wondering if there's a way to spin the mechanical tachometer using an electric motor, with its speed controlled by pulses from magnetic pickups on the crankshaft??? Either a variable-voltage controlling a simple DC motor, or an electronic driver running a stepper motor.

I want to keep the mechanical tachometer, but I'm working on a fuel injection system which eliminates the drive gear and cable on the right head.

Another thought is using the electronic-driven tach from a newer car. I installed a GT instrument panel in a non-GT Grand Am several years ago, and it had an analog tach that was driven off the coil signal. Hmmm... I would need to disassemble an 1100 tach without destroying it, then substitute the innards. Time for a junkyard run to find a 4 cylinder car, with a wasted-spark system, and with an electrically-driven analog tach. Any excuse for a trip to Pick-Your-Part!

As always, any ideas, suggestions, jokes, etc. are welcome and appreciated!

 

[Riding a Relic]

Sure there is a way to do it. You need a small analog generator, like the inductive type already on the goldwings. This will produce a sine wave. (not digital) In turn, it needs to be turned into DC voltage. This is what electronic modules do. Depending on the circuits, and the layout of the circuits, it does vary, on some car lines like the european cars, they vary wildly, that is the reason you see specialty auto shops doing only them.

I would stay away from mounting a car speedo. That would be more electronic guru stuff I wouldn't want to deal with, even. If you want a tach that will fit, go to a heavy truck parts website, motorola made many round tachs, and very easy to understand, just a little generator running another little motor (tach head) VERY simple and no bells or whistles.

Hope this helps!

 

[Riding a Relic]

GM and Dodge had inline "sensors" in speedometer cables to sense for transmission shift points on automatic transmissions and overspeed lights in the dash in manual transmissions. (to keep from mechanics having to remove valves from pistons )

 

[Riding a Relic]

Steve83, what kind of voltmeter or test meters do you have?

 

[Ansimp]

I would try to use an electronic tacho using your ignition pulse or one phase of the stator. I think an aftermarket one would be the easiest to use especially if you can transplant the mechanism into the Honda housing.

 

[Steve83]

Riding a Relic » Sun Oct 27, 2013 5:26 am[/url]":2gempypa]
Steve83, what kind of voltmeter or test meters do you have?

I have 2 meters, one digital and one analog. Both fairly basic. Someday, I'll repair or replace my old oscilloscope - it would come in handy.

 

[Steve83]

Ansimp » Sun Oct 27, 2013 5:42 am[/url]":1c0oqgss]
I would try to use an electronic tacho using your ignition pulse or one phase of the stator. I think an aftermarket one would be the easiest to use especially if you can transplant the mechanism into the Honda housing.

Yup, that might be the route I'll take. It would need to use an ignition pulse because the stator turns slightly faster than the crankshaft, I think about a 1.2:1 ratio.

 

[Ansimp]

Steve83 » Sun Oct 27, 2013 8:01 am[/url]":3i53h0mt]
Yup, that might be the route I'll take. It would need to use an ignition pulse because the stator turns slightly faster than the crankshaft, I think about a 1.2:1 ratio.

That is interesting about the ratio. With the correct aftermarket tacho the user sets the frequency and corresponding range to give a reasonable indication of the actual revs. I mainly use this style on Diesel engines using the alternator for the signal. I was telling Paul (C5) about an optical tacho that I use to calibrate these style tachos and also to check the accuracy of any tacho.

 

[Riding a Relic]

Steve83, there are plenty of old snap on vantage multimeter graphing meters on e-bay for reasonable cost. They are not true RMS scopes, but I use mine on circuits as needed. The shop owns a vantage pro but they are a lot more expensive, but do a lot more.