immobilizer control of VRS signal

[hcp474]

i'm trying to put to gether an immobilizer using an iButton and 08M picaxe (12digit serial key, with 8pin pic logic programmed with the relevent serial numbers). My plan is to place a solid-state switch of some sort at the junction where i'm attaching the additional cable to the VRS line. with a simple 1/0 from the logic to allow the signal to pass or block it.

i've a couple of analogue switches (solid state) MAX320CPA's so two divises to create redundancy. however testing these shows that the when inactive they still conduct a AC signal.

does anyone have any other sugestions for solid state switches that will conduct the AC VRS signal and allow 0/5V switching voltage?

i'll see if this chip works but i have my doubts (i've already tried one other variant...)

Thanks,
David

[Alexander_Monday]

An opto isolated triac comes to mind.

But if you have the hard rev limiter, why not "OR" with its input?

[hcp474]

The hard rev-limiter is a good idea, they were not in production when i bought my unit, should have waited and the new one would have come out; as its still awaiting installation.