voltage sensing relay (0-5 volt)?

Moby · 10-19-09, 09:45 AM

Not sure if this is the right forum for this but I'm going to take a shot...

I'm looking into replacing the (AFM) air flow meter on my FJ-62 with a programmable MAF unit. The main problem that I've got is that the OEM AFM unit has a fuel pump relay integrated into it. If the meter is not actually flowing air the fuel pump turns off to prevent dumping gas into the engine bay in the event of an accident. I realize that I could hack this with an ignition hot relay but that kind of defeats the intended safety feature.

What I need is the ability to trigger a relay based on any voltage > 0 (the AFM scale is 5-0 volts where 5 is low flow and ~0 is high). I've seen voltage sensing relays that go down to 3 volts but I need more resolution than that.

Any suggestions?

rusty_tlc · 10-19-09, 01:38 PM

Quote:

Originally Posted by Moby

Not sure if this is the right forum for this but I'm going to take a shot...

I'm looking into replacing the (AFM) air flow meter on my FJ-62 with a programmable MAF unit. The main problem that I've got is that the OEM AFM unit has a fuel pump relay integrated into it. If the meter is not actually flowing air the fuel pump turns off to prevent dumping gas into the engine bay in the event of an accident. I realize that I could hack this with an ignition hot relay but that kind of defeats the intended safety feature.

What I need is the ability to trigger a relay based on any voltage > 0 (the AFM scale is 5-0 volts where 5 is low flow and ~0 is high). I've seen voltage sensing relays that go down to 3 volts but I need more resolution than that.

Any suggestions?

Build an OP amp comparator circuit to drive the relay.

Moby · 10-20-09, 08:57 AM

Excellent, thanks! A quick search indicates that I have some studying to do