Fixed 2N2222 Highside Switch

132

03:04:30

Using a 2N2222 as a 12 volt switch on the highside with a 5 volt trigger.

published 5 years ago

Robert_Kidd

5 years ago

There are serious problems you need to address here. The most serious is the 2A flowing from the 5V supply into the transistor base. The transistor would fry in an instant. To overcome this add a resistor from the transistor base to the 5V supply. Also, note that while the switch is open (i.e. most of the time) the transistor base is floating - it needs a pull down resistor so it is held low when the switch is open. Make the base resistor 47k and pull down 1M.

TacoSleaze

5 years ago

Thanks for the heads up. I appreciate your input. I am running some math to figure out how to switch my 12v circuit with a 5v trigger. I keep trying different math and when I get something close, I try it on my breadboard. The 5v is actually the output from an RX480 board. I am using a remote to switch my circuit, but the RX output is only 5 volts. I don't want to add another relay.

Robert_Kidd

5 years ago

Did you understand my point about the resistor from base to ground?

TacoSleaze

5 years ago

I did. I threw it in there. Since these are sample switches and you are giving me excellent help, could you maybe help me with the final product? I know about voltage, resistors and caps, transistors are for me.

Robert_Kidd

5 years ago

You have pull down on emitter instead of base :-)

Robert_Kidd

5 years ago

Not sure exactly what you want me to do?

TacoSleaze

5 years ago

I think it works! I will let you know. Between you and a local engineer.....you pointed out a few mis-routed tie points. Saturday......back to the breadboard. Thanks you so much.

TacoSleaze

5 years ago

I also have a circuit called "Passive Tone Control", I need to know what I need as a test source and a meter. Do you have any ideas. Not sure if you know audio.

Robert_Kidd

5 years ago

Commented on that circuit.

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