Noob here. I've read "electronics for dummies" and that's about it
Anyway, what I want to do is close a +12V circuit for one device using only a +2V signal from another. Basically, I'm hacking an Audio/Video 4-input switch box and I want to close the +12V circuit if a specific input is selected. The switch box has 4 led's and one of them lights up corresponding to which input is the currently switched input.
I get +2V off the + and - leads of the LED.
So, I've taken a 2N3904 NPN transistor and wired it as so:
Emitter: +12V and +2V
Base: -2V
Collector: -12V
Now, this is my best guess from reading books and online articles such as this one on this site:
http://www.allaboutcircuits.com/vol_3/chpt_4/1.html
However, it's not behaving as I would expect. When the LED is turned ON, I get about +8V flowing out the collector. When the LED is turned OFF, I get +12V from the collector.
I was expecting: with the LED ON, +12V, LED OFF 0V.
UPDATE: Also tried swaping the Emitter and Collector to no avail (same results).
Where have horribly gone wrong?
I am fully expecting that I've done this completely wrong, so am now looking for some assistance.
Thanks!
David
Anyway, what I want to do is close a +12V circuit for one device using only a +2V signal from another. Basically, I'm hacking an Audio/Video 4-input switch box and I want to close the +12V circuit if a specific input is selected. The switch box has 4 led's and one of them lights up corresponding to which input is the currently switched input.
I get +2V off the + and - leads of the LED.
So, I've taken a 2N3904 NPN transistor and wired it as so:
Emitter: +12V and +2V
Base: -2V
Collector: -12V
Now, this is my best guess from reading books and online articles such as this one on this site:
http://www.allaboutcircuits.com/vol_3/chpt_4/1.html
However, it's not behaving as I would expect. When the LED is turned ON, I get about +8V flowing out the collector. When the LED is turned OFF, I get +12V from the collector.
I was expecting: with the LED ON, +12V, LED OFF 0V.
UPDATE: Also tried swaping the Emitter and Collector to no avail (same results).
Where have horribly gone wrong?
I am fully expecting that I've done this completely wrong, so am now looking for some assistance.
Thanks!
David