NC 9V LED circuit 2

[banderas]

I tried to build a simple LED circuit that is going to operate from 9V battery. When NC switch is closed I wouldn't want to draw any current, but this NC switch opens turns on red LED. Circuit I build was heating up the battery. My only requirements are low power consumption (so battery can last long time), fewer components-better.

Any suggestions?

Thanks in advance.

Banderas

 

[Skogsgurra]

Excuse me banderas. Are you serious? Or is this a fun thing?

You have identified yourself as banderas(Electrical) and that has to have some ground. One is that you have learned to connect a battery and a switch and a load in series - not parallel. Have a look at your circuit. And, BTW, do not forget a current limiting resistor in series with the LED.

 

[banderas]

skogsgurra,

Sorry if my question irritated you,but I tried to build something really simple to indicate when NC switch opens.And I got stuck.I tried pasting my circuit to forum the but it didn't work.I know how to to this with the logic gates but I don't have power available.Thanks for your reply.

Banderas

 

[Skogsgurra]

banderas,

I did not mean to be mean ;-)

But sometimes people try to be funny. I thought that you were. Sorry if that made you feel bad. Does it work now?

 

[OperaHouse]

You could add a npn transistor. Put the base and emitter accross the NC switch. Collector goes to 1500 ohm resistor, LED and then +9V bat. Negative goes to transistor emitter. This will give you 5 ma which won't be real bright. If the transistor has a gain of 100, you will need base current of 0.05 ma or 180K from base to bat positive. This will waste some current but not much. Get a transistor with twice as much gain and you can reduce the collector resistor to 750 ohms and 10 ma through the lamp.

 

[banderas]

Thanks for your help OperaHouse. This worked. I'll play with resistor values to get brighter LED.

Banderas

 

[BrianR]

I would have thought a 2 position switch would work pretty well here, the load to one position and the LED to the other....