basictransistors
I'm trying to learn about how transistors work. As a simple test I created the following circuit:
My idea is that when the second transistor will keep the first one active after I click the button for the first time, but it isn't. What am I doing wrong?
I might be totally wrong here but my excuse is the question is very confusing. The circuit shown above is trying to pull the 2.52 V line down to ground through the 10R resistor and an NPN transistor. The original (pre-hacked circuit) you describe was it this? Forward and Reverse are mutually exclusive as are left and right. On the vehicles I've hacked into they usually have a spring loaded centre off action (joystick). Are you absolutely certain the pole of the switch went to ground (0v)?
You say when you touched R2 (140k) the remote worked sending a signal to the car. This sounds like you were acting as an input signal. By touching the input your body as an aerial picking up the local EM field, the 140K resistor being large enough to prevent the weak signal from being shorted out. That suggests to me that the control input needs to go HIGH rather than LOW and that the switch was actually connected to the positive rail. To test this hypothesis connect up the circuit below and let us know what happened.
Any hints on how to fix that?
A circuit would help instead of text diagrams but to answer your question, try putting the 10k resistor in the collector of the transistor not the emitter; emitter to ground like the reset pin circuit, base as per reset pin circuit.
You may be able to confirm my suspicions if you can tell what your base drive circuit looks like.
EDIT following disclosure of circuit
If you swapped the positions of R1 and SW1 in your second diagram, the pushbutton circuit would still operate as normal BUT, significantly for the BJT this is a different ball-park; the BJT will switch on and drag the 10k down to ground.
Previously, when you tried the BJT in the original switch position you'd apply 3.3V to the base and approximately 2.7 volts would appear across the 10k resistor - this is because the base and emitter region act like a forward biased diode - even without collector current, the emitter voltage would be raised to 2.7V or thereabouts.
Best Answer
What you are trying to create is a thyristor and it is slightly different.
simulate this circuit – Schematic created using CircuitLab
To sustain a transistor on you need current through the gate, in this design the two transistors are feeding output through each other.