Tach signal from EDIS Pin 2

[jsmcortina]

The 64us pulses are so infrequent that your tacho won't show them. In the OEM install it was directly connected as far as I'm aware.

James

[scirturbo]

There's no need to filter them. My tacho responds to them but all you hear is a sound like a ticking clock. You can just see the needle move a bit.
Be aware that this signal is a 12v square wave so it could be that your tacho won't work. I simply bypassed the  limiting resistor at the input to make it work.
 
SFC 

----- Original Message -----
From: midnightblue (midnightblue@durys.co.uk)
To: megasquirt-msedis@msefi.com (megasquirt-msedis@msefi.com)
Sent: Friday, October 28, 2005 7:34 PM
Subject: Tach signal from EDIS Pin 2



I'm looking at using pin 2 from the EDIS module to provide a tach pulse to drive my stock tachometer.

I have been reading http://www.dainst.com/info/edis/edis.html particular;y the bit that says "The EMF flyback from the coil then triggers the IDM of the EDIS module and causes it to emit a tach pulse on the IDM pin."

It goes on to say further down: "The IDM signal is triggered by the flyback voltage of the coil being fired. The EDIS module processes this into a 512us pulse on the IDM line during operation. When the engine is stopped, but the Key is turned on (KOEOff), the EDIS module emits a 64us pulse every 262.144ms to indicate proper operation. Because of this, any tachometer operation from this line must filter out the 64us pulses."

This looks like it will do the job nicely, do any of you electronics gurus have a simple idea for filtering out those 64us pulses, and leaving the useful 512us to trigger the tach?

Many thanks, Matt



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