i wonder if you could achieve the same thing but using solid state components?

 

a chunky transistor instead of the relay?

i wonder if you could achieve the same thing but using solid state components?

 

a chunky transistor instead of the relay?

 

that little relay board runs on that concept, but uses the relay to switch a 30 amp load. So you could use a small transistor and a big one, in an Amplification type circuit to switch earth to the coil.

yep thats what I'm thinking.

 

solid state= it will run forever...

 

Assuming that there isnt any crazy EMF business coming out of that coil which will blow up the "big" transistor.

 

though i reckon that the relay will go for a pretty long period of time as well. not like you are going to be on the limiter all the time? think about how many times the indicator relay clicks!

 

i also wonder about the possibility of desigining the circuit so that it doesnt do what taz explains (the chattering of the relay, constant off and on). put a small capacitor in there somewhere, so when the relay activates it stays on for say 1/4 second minimum. maybe? i dunno...

I've had a look at one of my unfinished projects, a programmable ignition system. It comes with an Ignition coil driver which allows you to use a very small trigger current to earth out the coil, it has built in zener diodes to stop massive spike voltages from damaging the main transistor. To make the signal last a little longer, you could use a capacitor charge and discharge circuit, unfortunately it's been some years since i studied this type of circuit. Am doing it at uni in a couple of weeks so i will be refreshed. Might look into that, have info on it somewhere

Thanks heaps guys, i like the tacho idea a lot

Since your just sending an earth to the coil there would be very little current flow through the relay, relays endure millions of cycles and normally die of age (age as in time) or when brand new from incorrect manufacturing.

 

Its not so much the load that it has on it, its the speed of the cycles. Yeah I realise relays can go through millions of cycles in the life time, but they normally don't have to switch on and off so many time in a short space of time.

 

An ignitor could deffinately handy the load and quick switching (as thats what they do) but the problem is they don't have an "87a" equivalent to let current flow through a secondary circuit when the ignitor is not triggered.

 

doecke55 - RE PM, click on the link trev posted and there's diagrams on pages 3 & 5.

Thanks, umm is that the one where there is no risk of misfiring and catastrophe