Hi,
I'm trying to steal another switch position by using the middle of a ON-OFF-ON switch.. so I'm looking to flick a relay when the switch is disconnected in the middle position.
Not sure the best way to do this.. I've been thinking something with a 2N7002 maybe would work.. My FET knowledge is a bit rusty ... I've attached a circuit I drew up which I think would work but unsure of any potential pitfalls. Would I need some protection on the gate or is the 16V (regulated DC supply) small enough, it'll be ok?
Hi,
I'm trying to steal another switch position by using the middle of a ON-OFF-ON switch.. so I'm looking to flick a relay when the switch is disconnected in the middle position.
Not sure the best way to do this.. I've been thinking something with a 2N7002 maybe would work.. My FET knowledge is a bit rusty ... I've attached a circuit I drew up which I think would work but unsure of any potential pitfalls. Would I need some protection on the gate or is the 16V (regulated DC supply) small enough, it'll be ok?
where is the relay in your diagram? If it is the "1000 load" then 2 points.
1/ you have drawn the symbol for a resistor not a relay coil.
2/ more important, the 1N4148 diode will not be suitable for this circuit, you need a diode which can handle much more current.
I would suggest a 1N4002 or even a schottky diode with at least a 1 amp rating.
Norman
I see what you are saying so maybe I have misunderstood this. I thought that the back emf could be quite high and so no matter what the current through the relay coil, when it is interrupted, the voltage could be quite high and so the initial current could possibly be much higher than the steady state current. In which case, if I am correct, it could easily exceed the rated current for a 1N4148.
I see what you are saying so maybe I have misunderstood this. I thought that the back emf could be quite high and so no matter what the current through the relay coil, when it is interrupted, the voltage could be quite high and so the initial current could possibly be much higher than the steady state current. In which case, if I am correct, it could easily exceed the rated current for a 1N4148.