Hi!
I have one transistor (NPN, I think, C945).
Also I have a battery that I yesterday filled with new electrolyte (the battery was dry). The battery is very similar to a car battery (12V), but I took it from an old UPS.
What I want to make is make a LED light on when 1V is added.
What I tried is add the +12V to Collector, -12V to Emitter and a lightbulb right after the transistors Emitter, but it didn't light on when I gave +1V or +12V to Base.
Maybe someone can explain bit how it is supposed to be done?
I found a nice app called Multisim, I used it to get the result, but not sure if this is also true in the real life... **broken link removed**
What I don't have is a ground (a armature in the ground) and nice looking wires, also not the 5V bulb, it is only for testing if there are some volts in the Base.
But I have a problem by the start.
If I put Collector to + and Emitter to - the I also get the 12V, even without Base.
Is this OK?
And how do you mean the ground side of bulb?
Place the +12 to the bulb, the bulb to the collector, then the emitter to the negative side of the battery.
This way you are making a "low-side" switch, which will do what you are looking for. The way you have it is called a "high-side" switch, which requires more voltage at the base before it turns on.
Ahh, I didn't check the max current. It is now dead... I guess, but the multimeter still shows some value, so not dead yet?
I have a battery with 12V, like I said, and max current of the battery is... well I don't know exactly, but is is said 12V8.2AH/20HR so it can do 8.2A for 20 hours?
What would you recommend me to do? The power of the bulb is unknown, but I will get a new one anyway, so you can choose... 1W, 5W...
The 5V/1W light bulb in series with the base of the transistor will draw about 200mA in the base of the transistor that will blow up the transistor.
The 12V/25W light bulb will draw 2.1A which will also blow up the transistor.
Actually, the light bulbs draw about 10 times the current when they are cool.
Your battery is 8.2Ah at a 20 hour rate so it supplies 0.41A for 20 hours.
It might supply 8.2A for a minute or two.
"Just before the transistor" means nothing.
Where is the resistor and what is its value?
Is it in series with the base of the transistor?
Are you still trying to use a puny little transistor when you need a power transistor?