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Smiths Telemetrix tacho + megasquirt
Bizarro - 7/8/12 at 10:28 AM

Im using a Megasquirt that has a tacho output connected to a Smiths Telemetrix tacho.

I have successfully started the car and have it ticking over but do not get anything on the tacho. Using the search facility on the forum I have found a post saying tacho out from a Megajolt does work with a Smiths gauge without modification.

Before I look into modifying with resistors/relay or driving the tacho from the coil pack has anybody successfully used the 'tacho out' from a megasquirt with smiths telemetrix gauge? Dont want to spend time messing around if there is a simple solution!

Cheers

MikeRJ - 7/8/12 at 11:14 AM

What ignition system are you using, built in drivers or an EDIS unit?

Bizarro - 7/8/12 at 11:29 AM

quote:
Originally posted by MikeRJ
What ignition system are you using, built in drivers or an EDIS unit?


Ford zetec coil pack driven directly from Megasquirt, not using EDIS.

big-vee-twin - 7/8/12 at 12:13 PM

Have you built the amplifier circuit, as the MS board does not have the correct output to drive a tacho direct, you have to build a transistor circuit inbetween the MS and guage.

Personally I have not heard many have success driving a tacho from MS so I chose to drive mine direct from the coils using the below circuit, the guage worked immediately the engine started.

I'm using Smiths Classic guages


[img] tachometer diodes
tachometer diodes [/img]

Bizarro - 7/8/12 at 02:36 PM

quote:
Originally posted by big-vee-twin
Have you built the amplifier circuit, as the MS board does not have the correct output to drive a tacho direct, you have to build a transistor circuit inbetween the MS and guage.

Personally I have not heard many have success driving a tacho from MS so I chose to drive mine direct from the coils using the below circuit, the guage worked immediately the engine started.

I'm using Smiths Classic guages


[img] tachometer diodes
tachometer diodes [/img]


OK thanks, just ordered some diodes and Ill give it a go.

Silly me thinking it would be as easy as connecting the wire marked 'tacho out' to the tacho and it would work!!

big-vee-twin - 7/8/12 at 04:44 PM

The output of the circuit is the same as if you took the pulses from a single coil so set your tacho to 4 cylinder single coil