Finding contact points

[bustinthejustin]

Hey how would I find points with a multimeter, for example, ground, positives, etc. I want to know this for future reference just in case. Also, if a positive point only gives out about 2v, but I'm using a blue led that runs on about 3v, Would it be too dim or would it work okay?

[802Chives]

In order trace out contacts and what not you need to start with a known point in the system, that would be ground or battery negative.  With the ground point you will be able to test other points for voltages and signals using the ground as ur reference(negative lead) Also a continuity checker will be usefull to see what points are common to eachother.

2v trying to run a 3V led probably won't work. sometimes they will work if you operate close to there forward voltage like 2.9v on a 3.0v diode might work, but there is no garuntees.  When leds are super dim, they are still being run at there full forward voltage, the only thing that is less is the current through the led. typically LEDs have a working current of 20-30mA and if you run them with say 1mA, that is will make em dim.

[bustinthejustin]

Is there a good way of finding a ground?

[802Chives]

the internets is a good place to look, or battery negative is sometimes ground (but not always, sometimes its switched).

[bustinthejustin]

Okay, thanks. One more thing. If I'm not getting enough voltage from a point, how would I increase the voltage?

[802Chives]

increasing voltage is not a task that many people will be able to accomplish. For starters there isn't really a good clean solution available for a modder since it is usually a DC situation, however there are many thousands of possible ways to get it done.  Most simply, you could add an extra powersource, like coin cell batteries to get you desired voltage.  There are two other very general ways to go about producing the additional voltage, a Switched Capacitor Boost style circuit which tends to only be able to supply low current, and there is a standard Switched Step-up Regulator circuit which utilizes an iductor instead of a capacitor as an energy storage medium.  Both ways require numberous components that are usually surface mount, which means they require a PCB to install them.

In a AC situation, things get a little simpler with the use of a step-up transformer and rectifier circuit, however this is bulky and impractical with most designs.

If you have a specific design task in mind I can put the thinkin cap on and see what we cant do.  If it is the 2V for a 3V led we may be able to figure a simple capacitive boost circuit to do the job, but it will use several diodes and capacitors so if space is an issue it may not work.  Let me know what the details are and what you are working on and will see where to go from there.

[bustinthejustin]

Thanks a lot. Well currently I'm not really working on anything, I'm just getting some knowledge for future reference, but I was just thinking that a lot of things use red leds for indicator lights and that only runs on about 2v. I was just wondering how I would swap that to a blue led.

[Alien_X]

Usually there is a resistor between the voltage source and the led - like the psp power switch board.

[bustinthejustin]

So I'd have to do some continuity testing between all resistors near my voltage point, and the voltage point, and when I do find continuity, bridge it and hope for the best?

[Alien_X]

Measure the voltage without the resistor and the led drawing/increasing resistance - (basically short it through your multimeter around the two components)
Then you work out the correct resistance needed, and replace the resistor.

[bustinthejustin]

So use the multimeter to short the resistor by using one on both contacts of the resistor and the other to measure the voltage without the led, then replace the resistor with my own?

[Alien_X]

Not really.
I think someone better at explaining things needs to help here.
Also, I suggest you read an electronics textbook and search for how to use a multimeter.

[bustinthejustin]

*shrug* I know how to use a multimeter. Perhaps not as well as I could, but I get by. Oh well thanks for trying. Retarded people don't learn well