Please excuse what may be a simple question, I am very rusty when it comes to electronics having not looked at them at all for about 25 years! I hope someone can resolve my query.
I have a circuit design that takes a switch connected to ground. When closed the LED is on, when open the LED is off.
In this diagram the shaded switch and LED are part of a larger existing circuit which cannot be changed. The LED is just an example of my load.
What I want to achieve is to swap the action of the switch around. I want the LED on when the switch is open.
I could do this easily with a relay but I haven't got the physical space for a relay, I'm sure it can be achieved with transistors but I'm not sure how!
Best Answer
The easiest method is to remove the transistor and both resistors connected to the base of the transistor (10k, 47k). Then connect the free end of the switch to where the collector used to be.
If this is an existing circuit board, remove the above components. Then install a jumper where the 47k resistor used to be and another jumper between where transistor leads B & C used to be.
The circuit function remains similar with similar power consumption.