TI used to make a dedicated speedo/tacho chip (SN76810) for driving moving coil meters, the input pulses were conditioned by a monostable whose output drives a simple constant current circuit.Yes the circuit board needs an earth to the engine. Yes assembled the kit yesterday, it has been siting around un assembled for quite some years. Over the years ive used a lot of the LM2917 chip in analogue tachos for diesel engines using a Hall pickup.
LM prefixes are usually National Semiconductor - and they look like audio amp chips IIRC.It seems Texas has free samples. Sweeeeeeeet!
I am getting some 14 dip and 14 Soics, 3 each. Should be enough to test.
Just yesterday they sent me
LM3886T & TF
LM4766T & TF
LM4780
Each 3 pcs total of 15 pcs.
Most motorcycles use the wasted spark ignition so the plugs fire both on the intake and exhaust stroke (the latter spark doing nothing, hence the name wasted spark).This is not by any chance auto motive modification even though you dunno what I had in mind.
Having said tht, I was wondering about this idea last night.
I wanted to read the engine RPM without taping into the harness.
I believe I can take the pulse by placing a coil on the spark plug wire.
The high voltage can induce enough voltage in the coil to make a pulse each time the coil generates a pulse, right ?
Question is what is the pulse count for a 4 stroke engine.
How many pulses would be produced by one engine rotation?
correct. The low voltage side (primary) winding on the coil was used for driving the tach.Why not use the connection to the primary side of the coil and be done with it? This is how most original equipment and aftermarket tachs were driven
National Semiconductor was purchased by Texas Instruments, and TI didn't change the LM prefixes after the purchase.LM prefixes are usually National Semiconductor - and they look like audio amp chips IIRC.
Those are audio amps ICs.It seems Texas has free samples. Sweeeeeeeet!
I am getting some 14 dip and 14 Soics, 3 each. Should be enough to test.
Just yesterday they sent me
LM3886T & TF
LM4766T & TF
LM4780
Each 3 pcs total of 15 pcs.
by Jake Hertz
by Duane Benson