[SOLVED] need a circuit idea that flips an off to an on and on to an off type idea.

[sdowney717]

looking for a circuit that when goes open circuit from a ground, it conducts.
So imagine, if a grounded switch is turned off (grounded state breaks to an open circuit, it closes a complementary circuit. like a transistor conducts from E to C

Not a relay, if needs to be a semiconductor switch. It will be low voltage 10 to 15 vdc, and low milliamps, maybe a couple hundred at most milliamps are on the switch connected to ground.

So if on, it turns off something, and if off it turns on something.

 

[barry]

Is this a trick question? Am I missing something? If you have a common-emitter PNP transistor, pulling the base to ground through a resistor will turn it on. Or use a P-channel MOSFET.

 

[Vbase]

looking for a circuit that when goes open circuit from a ground, it conducts.
So imagine, if a grounded switch is turned off (grounded state breaks to an open circuit, it closes a complementary circuit. like a transistor conducts from E to C

Not a relay, if needs to be a semiconductor switch. It will be low voltage 10 to 15 vdc, and low milliamps, maybe a couple hundred at most milliamps are on the switch connected to ground.

So if on, it turns off something, and if off it turns on something.

This circuit could be what you want. When the sw is open that allows current to the base of TIP31 to switch it on and enable current through the load. The transistors can be replaced by equivalents. TIP31 can drive 200mA without getting hot.

 

[barry]

Vbase is right. I had it backwards.

 

[sdowney717]

Thanks, dont try to out think me, not a trick question, I fool myself too.

I worded this way to try to approach the problem circuit another way as I was getting no where with my thinking.
I eventually did get it to work using an NPN transistor.

This is an ignition point saver circuit using a GM ignition module. the modules all fire on points closing, and it needed to fire on points opening.
And now it does.
I started here, but the circuit had a major error, terminal W is shown as BAT+, when it should be grounded.
**broken link removed**


This circuit solved the module firing on points close


And adding in the NPN trans circuit from the first site, then makes it fire on points open.
So it works fine now.
Here is my completed ignition circuit for the Onan generator two cylinder.


This will save grief and trouble as the points with very low current loading will last very long time.