For all you electronic tinkerers, I’m posting a circuit diagram for an adjustable rpm switch. It’s something you can use to activate solenoids for auxiliary ports, VDI, shift light, or anything else you can think of. The circuit is adapted from a rev-limiter circuit for rotaries.In particular, I’d like to thank Rob Weinstock from the fc3s.org list for his help tweaking it. I built and installed two of these switches in June when I did a VDI swap, and so far they’ve been working fine. Parts cost per switch is only about $10 CAD! Note my installed photo, I’ve mounted them away from heat, as I don’t know how that might affect the components. Also, not shown in the circuit layout, I added LED indicators for power, and the ‘switched on’ state.
One other note – I had been looking at the S5 FSM, and noted that the aux. ports and VDI only operate under load. I have a GXL, which came with auto-adjusting suspension. Part of that system is a switch on the accelerator pedal, which sends a 12V signal to the AAS computer above about half throttle. To approximate the ‘under load’ effect, I took the 12V power for the rpm switches from this switch, so they only operate when I ‘floor it’. Just something you might want to try if you’re doing the VDI swap or changing your aux. ports to electronic activation.

 

circuit schematic:

 

installed switches:

 

Great Work! I wish this would've came along a while ago when I was looking around for them... $50-70 a pop my ***!

 

Archive! Archive! Archive!

 

Nice work

 

So which LM2917 are you using???

Your diagram/Circuit design calls for just a LM2917, but it looks like a LM2917N in your pictures.
and if so, is there any reason that you are not using the LM2917N-8 instead of the 14 pin

 

its the lm2917m or n

 

I used the 14 pin as per the diagram, left the unused pins 'n/c' (not connected). I can't say if substituting the 8 pin is acceptable, but the 14 pin is only a couple bucks anyway. I'm not presenting myself as an EE, I adapted an existing circuit design into a workable alternate design. Refinements welcomed!!!

Curtis
'86 GXL autox'r

 

The pics aren't there.

 

The pictures fade after a couple of years after the initial posting.

 

Why do these things dissapear as you need them

anyone got links to the old diagrams or know where they have dissapeared too?

 

Chopmasta to teh rescue!

 

and just for backup...

 

I wish I knew how to build things off of those cool little diagrams. Time to learn, eh?