convert negative pulse into positive using a transistor?

hello... ive built an scr using transistors to turn on leds in my car with my remote.. my remote uses negative pulse.. now the scr(latching transistor) that ive built turns on with a positive pulse and off with negative.. so turning it off is not a problem.. I need to change the negative turn on pulse to positive to turn it on though. I know theres a simple way using a transistor to do this, but im still learning and my knowledge of transistors is still limited.. here is the schematic I used.. figure 75 b. I followed the schematic and it works just fine..http://www.talkingelectronics.com/projects/TheTransistorAmplifier/TheTransistorAmplifier-P2.html#Latch  ... thanks for helping me out here

sort by: active | newest | oldest
iceng3 years ago
I invert a pulse with a transistor this way
aclark32 (author) 3 years ago
ok,, so I figured it out.. all I needed was a pnp transistor (2n3906),, im not quite sure yet how it works, if somebody would care to explain whats happening here I would love to hear the official explanation...but heres the connections I made.. the emitter goes directly to +12v, the negative side of the led(cathode) goes to - ground, the collector connects to the +(anode) through a 330 ohm resistor, and the base is the input through a 10k resistor.. im going to make an instructable for this as soon as I figure out how to do that.. thanks guys for seeing me through this..
What do you mean by "negative pulse" negative in time or voltage ? Can you draw it ?
aclark32 (author)  steveastrouk3 years ago
im not sure what you mean..lol.. im still in the learning stage.. heres what I need done.. My remote starter on my car uses negative pulses from the lock and unlock wires to lock/unlock the doors.. I built the transistor scr that I referred to above and it works,but it needs a positive pulse to turn on(without the switches in it of course), but it turns off when ground is applied to the off switch. I am trying to turn on leds in my car with these wires.. so when I press the unlock button it send a ground pulse to the scr which turns it off just fine,, but the problem is to turn on the scr it needs a positive pulse from the lock wire..what I need to do is make the negative(ground pulse) from the lock wire positive.. I could use an automotive relay to this easily, but the whole reason I built the transistor scr is to avoid using all the relays and make it a small package...Im pretty sure this could be achieved by using a transistor but I haven't been able to do it.. I hope ive made what I need clear.. I just cant think of a better way to explain it.. ill try to draw something up to show what I need to do.. thanks again
So the line is 12volts, drops to 0 volts, then goes back to 12 volts? Not actually negative.
aclark32 (author)  steveastrouk3 years ago
no the line rests at 0 then goes to ground and back to 0... I need to use a transistor to make it go to +12 then back to 0.. heres a quick picture I drew up to help explain...it also has a diagram of the way I would wire a relay to do it if that helps....
aclark32 (author)  aclark323 years ago
heres the picture
my circuit.png