OK then lemme buy some LM2917

 

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.

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.

These days its hard to even find the datasheet for that device!

 

Most of the early tachos and auto tune up meters used a two transistor monostable, and a zener diode as the "voltage regulated" supply. That is all you need to turn a frequency into a DC voltage to run the moving coil meter.

 

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.

 

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.

LM prefixes are usually National Semiconductor - and they look like audio amp chips IIRC.

 

It appears Texas inst are using these part numbers & yes they are all Audio amp chips.

 

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?

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).

On a two cylinder bike engine, you het a spark on each RPM because the pistons run together. On a four cylinder, I think you get two sparks per revolution since the piston sets are 180 out of phase..

 

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

correct. The low voltage side (primary) winding on the coil was used for driving the tach.

 

LM prefixes are usually National Semiconductor - and they look like audio amp chips IIRC.

National Semiconductor was purchased by Texas Instruments, and TI didn't change the LM prefixes after the purchase.

 

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.

Those are audio amps ICs.

 

You did not read my post. I said I requested for the LM2917 Dip and soics.

And I said I got a previous order and I got em yesterday.
Yes the order I got was for Audio chips. They are for the speakers I have in mind.
Remember the LM3886 thread. I bought something I can get for free.

 

And guess what ?

I requested for LM2917N and I thought why not make my cart full . so I requested some more LM3886 just to see what happens, and today I got the fedex tracking mail. They sent it again. Now me got more than I bought for free.

These ti guys are great.
I bought 5 LM3886TF for like 15 bucks.
Now I got 6 pc LM3886T and 6 pc LM3886TF for free. Who can beat tht ?

 

Guess what.
Me got the above package

Time to proto the converter.