circuit help, push button--> light turns/stays on

[itshayhaysturn]

NOW THAT WORKS!

i was under the impression that i was supposed to add a resistor on a pre-existing wire, which was a really stupid thought, but now i understand, and the best part is it WORKS! thanks a bunch for helping me!

i have recently been trying to make a project myself and i need part of the project to work as a push button stays on just like the circuit u were working on, I DONT UNDERSTAND really anything!!! i have tried for weeks to make what u have accomplished, dont understand why 5 ma is m for million when it is in the thousandths place .005 10,100,1000 ths place u know what forget it i am getting off what i want to ask you. why does the circuit need the r4 resistor, i am currently using the circuit to drive a relay i removed the r1 and led and put a relay in place. i read everywhere where it says to put a diode in parralel and when i do that the diode burns up do u know why? i saw somewhere where they put a capacitor in parallel what does that do when i do that the circuit seems to work just fine. also is their anyway to get more current and voltage to my relay, what i mean is i have a 12v supply when relay hook up direct i loose 2v and it uses 144ma when in the circuit i loose 5v and it uses 122ma and the relay seems to run hot maybe it is supposed to be that way i dunno. i am really lost and i am having a hard time with understanding the math. if .005 is 5ma then what is .0005 when .000005 is 5 ua blah if u just answer the r4 question that little bit would be much appreciated and u dont have to answer anything else if u dont want i will just probably keep asking more questions thank you

 

[ccurtis]

i have recently been trying to make a project myself and i need part of the project to work as a push button stays on just like the circuit u were working on, I DONT UNDERSTAND really anything!!! i have tried for weeks to make what u have accomplished, dont understand why 5 ma is m for million when it is in the thousandths place .005 10,100,1000 ths place u know what forget it i am getting off what i want to ask you. why does the circuit need the r4 resistor, i am currently using the circuit to drive a relay i removed the r1 and led and put a relay in place. i read everywhere where it says to put a diode in parralel and when i do that the diode burns up do u know why? i saw somewhere where they put a capacitor in parallel what does that do when i do that the circuit seems to work just fine. also is their anyway to get more current and voltage to my relay, what i mean is i have a 12v supply when relay hook up direct i loose 2v and it uses 144ma when in the circuit i loose 5v and it uses 122ma and the relay seems to run hot maybe it is supposed to be that way i dunno. i am really lost and i am having a hard time with understanding the math. if .005 is 5ma then what is .0005 when .000005 is 5 ua blah if u just answer the r4 question that little bit would be much appreciated and u dont have to answer anything else if u dont want i will just probably keep asking more questions thank you

R4 is there to develop a voltage drop when the circuit is latched to ensure that Q1 stays on when the pushbutton is released. The more puzzling question is what R3 is for? It can be replaced, and typically is replaced, with a short circuit. The resistor added later (indicated by a red arrow) is not necessary if the emitter of Q2 is connected to the top of R1, rather than to ground, and R2 should be replaced with a short circuit and instead connected between the base and the emitter of Q2 to develop a holding voltage drop for Q2 the same way that R4 does for Q1. Make those changes and you should not lose 2V, more like 0.7V.

The parallel diode you installed accross the relay (coil?), I suppose, was installed backwards. That would cause it to burn up. A capacitor is sometimes placed across R4 and/or R2 of the circuit described above to prevent false triggering when power is turned on.

Relays can run "hot". As long as you are applying the correct voltage and provide room around the relay for it to dissipate heat, you should be okay.

ma means milliamp, or 1/1000 of one amp, thus 0.001 amp. Capital "M" means million, mega. small m means 1/1000, milli.