I know everyone wants to remove noise and spikes from square waves but I want to add one!
12v square wave input, say 60ms period (will vary) assume ramp up is quite fast and I guess that speed will have an impact on the spike peak. I want a up to a 30v peak spike on the leading edge. I've only got 12v (14.5v at times) to play with.
Any suggestions?
Thanks
I've tried simulating with and inductor and diodes and can create a spikey wave but always <12v

 

Maybe you ought to tell us why you need to do this.

 

I want to drive a rev counter with the square wave. Some versions of the rev counter work on a clean sq wave. Others don't work on a clean wave. The coil normally give a spike higher than 12v which I can reproduce on a bench setup.

 

I think you might be confusing cause and effect.
Have you tried increasing the voltage of the driving signal?

 

I can't as the driving signal is 12v already or 14.5v when engine running.

That's why I was considering a spike to get a higher voltage

 

Specs of the counter, please.

Edited to add: If this is an electromechanical counter, 60 msec might be too fast for it.

 

Maybe whatever is generating the signal has a high output impedance. Try using a MOSFET to drive the counter.

 

What specifically do you want to know?

 

Specs of the counter, please.

Edited to add: If this is an electromechanical counter, 60 msec might be too fast for it.

At 1000 rpm there's 2 periods per rev = 30ms period - higher revs 600rpm 5ms period

 

Can you post the make and model of the counter and perhaps a photo?

 

Motometer or VDO brands

 

Ok. This is an RPM tachometer. Does it have odometer readout?
I am going to assume that this is not a mechanical counter. My first guess is that it is a 555-timer circuit that integrates pulses to drive an analog display meter. But I could be wrong.

Next question is, what device is sending a signal to the tachometer?

Here are examples of 555-timer tachometer circuits.

 

Signal is coming from a CAN to 12v square wave converter.

tacho only, no odometer

 

Is there any chance of seeing the reverse side of that printed circuit board?

 

The chip on there is a SAK215 -https://www.tekkna.it/index.php%3Fdispatch%3Dattachments.getfile%26attachment_id%3D2308&ved=2ahUKEwi3vI_jpMKHAxWuUkEAHddiOuUQFnoECCkQAQ&usg=AOvVaw3xKEM0EgGSQMCiTp7Wd2m8

 

Here is a slightly different version that I can do a pic of the back

 

the image shows something quite ancient. so if it was working before, something must be wrong with the unit itself. i can see that the trimmer is oxidized and electrolytic caps must be out of spec by now. i would be replacing them rather than trying to modify how the circuit is supposed to operate.

 

the image shows something quite ancient. so if it was working before, something must be wrong with the unit itself. i can see that the trimmer is oxidized and electrolytic caps must be out of spec by now. i would be replacing them rather than trying to modify how the circuit is supposed to operate.

They do work with the standard setup, no problem - circa 1984. But they don't work with a 12v square wave. I have other versions that do work with both however.

 

 

That looks perfect - thanks very much - I'll need to build a prototype. Any specific specs on the components I need to know?