Spark plug wire inductive pickup for RPM
Spark plug wire inductive pickup for RPM
(OP)
So recently I've seen several devices that have a pretty neat way of interfacing with most modern day combustion engines. Instead of complicating the installation of a device with having to find an RPM pickup to splice into(coil trigger, engine position sensor, etc) several manufacturers are suppling their devices with a one wire inductive pickup. They instruct the user to wrap the end of the wire around the spark plug wire several times (7 I think). Specifically, many hour meters use this style. This is very neat if you can actually determine RPM from it (some do some don't). I technically don't need to read RPM (which is a lot easier) but I would like to have the capability in the future.
I could wrap some wire around a spark plug wire myself and do the test to capture the waveforms but I figured I'd stop by here first. Has anyone successfully built the analog circuitry to condition this signal into something TTL compatible?
Here is an example:
http ://www.tin ytach.com/ tinytach/i nstallatio n_gas.html
Thanks guys
I could wrap some wire around a spark plug wire myself and do the test to capture the waveforms but I figured I'd stop by here first. Has anyone successfully built the analog circuitry to condition this signal into something TTL compatible?
Here is an example:
http
Thanks guys





RE: Spark plug wire inductive pickup for RPM
Be careful not to put your signal wire close to other ignition cables - it will easily pick up enough signal to confuse your counter if you do.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Spark plug wire inductive pickup for RPM
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Spark plug wire inductive pickup for RPM
Not sure if large trucks have OBD, but most of them are diesel and wouldn't have spark plugs wires either.
Some modern cars have the coils right on the spark plugs, so no distributor and no spark plug wires.
RE: Spark plug wire inductive pickup for RPM
I used LMC550s. The first was setup as a unity buffer. The input was DC biased to the center. The input was capacitive just like the above examples.
The buffer was followed by a comparator that just squarewaves what the buffer puts out. Then you just look at the squarewaves.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Spark plug wire inductive pickup for RPM
LOL
Bill
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"Why not the best?"
Jimmy Carter
RE: Spark plug wire inductive pickup for RPM
Hopefully someone axed it for me.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Spark plug wire inductive pickup for RPM
Keith Cress
kcress - http://www.flaminsystems.com