The rev counter issue

EDIS and Megajolt installation related topics. Be sure to review the <a href="http://www.autosportlabs.net/MJLJ_V4_vehicle_installation_guide">Vehicle installation guide</a>

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jano
Posts: 5
Joined: Tue Dec 26, 2006 3:57 pm

The rev counter issue

Post by jano »

I have a SMITH RVC rev counter that I'm trying to get working with megajolt.
I have built the suggested circut with the zeners and even purchased the prebuild thingy from triggerwheels, but I can't get it to work.

When the engine is at idle, the rev counter shows about 1500 rpm, but when increesing the revs the needle drops to zero like a hammer and stays there.

The homemade version goes to about 2500 rpm before the needle is pulled to zero, the one one from triggerwheels drops instantly when accelerating.

What am I doing wrong?

/jano

[email protected]
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Joined: Tue May 05, 2009 8:06 pm
Location: East Yorskire
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Post by [email protected] »

Don't start me on rev counter woes.... I just found out mines current driven not pulse !

Anyway this is about your problem rather than mine - Have you tried the circuit with the Zener removed (just the two diodes)
If at first you don't succeed use a bigger hammer
*************************************
'89 TVR 400SE V8 "Wedge", now Jolted see Powered By !

NITROPIXIE
Posts: 704
Joined: Sun Sep 07, 2008 1:54 pm
Location: Fareham, GB

Post by NITROPIXIE »

Try Pin 11 of the EDIS module. This is the CTO or Clear Tacho Output. Sometimes there is not a pin 11, in this case you can also try pin 2 which is the IDM. This is a diaognostic output which emits a 500rpm signal when the EDIS module has power applied and then an a signal representing rpm when the engine is started. This could be used to confirm the EDIS has 12v when the ignition is switched on.
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Gilesy998
Posts: 144
Joined: Tue May 16, 2006 4:35 pm
Location: Liverpoool, UK

Post by Gilesy998 »

Have you tried the simplified tach diode circuit? Basically touch your tach trigger wire on the INPUT of the Zener diode, eliminating it from the circuit. I know of people that have had good success with this after getting exactly the problem you describe regarding the needle hitting a wall and dropping to 0.

jano
Posts: 5
Joined: Tue Dec 26, 2006 3:57 pm

Post by jano »

I'll try to kill the Zener.

also I found this one http://www.autosportlabs.org/viewtopic. ... r&start=30 looks very much like my scenario and suggests to wire the rev counter directly to the PIP signal.

/jano

alhbln
Posts: 29
Joined: Sat May 31, 2008 3:40 pm
Location: Germany
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Post by alhbln »

[email protected] wrote:Don't start me on rev counter woes.... I just found out mines current driven not pulse !
This might help:
www.dinoplex.org/tachoconversion/

[email protected]
Posts: 28
Joined: Tue May 05, 2009 8:06 pm
Location: East Yorskire
Contact:

Post by [email protected] »

alhbln wrote:
[email protected] wrote:Don't start me on rev counter woes.... I just found out mines current driven not pulse !
This might help:
www.dinoplex.org/tachoconversion/
Thanks I found that,

I took it apart and found that it was a Stewart Warner instrument that had a proper iron cored transformer on the coil feed to convert current pules to voltage pulses. So I cut the track after the transformer and added a zener + 1K resistor and injected the pulses into the tach and it works perfectly, just tested it at work with a square wave generator !

Saved £75 !
If at first you don't succeed use a bigger hammer
*************************************
'89 TVR 400SE V8 "Wedge", now Jolted see Powered By !

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