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LED's

When using an LED formation, with a picaxe and added sensors, servos, and motors that is powered by four AA batteries, does that change what the source voltage for the LED formation would be? And would it be possible to add this LED formation to the start here bot at one of the output pins so you could control the blinking of several LEDS instead of one at a time. Or if there is a better way to accomplish this could you please enlighten me?

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Chris the Carpenter's picture

http://letsmakerobots.com/node/4948

The above link should give you all you need --series, parallel etc (and all the math). However, you will eventually get to a point where your picaxe output can not handle the current... Gotta start looking at a n2222 transistor or a darlington chip.

Ian_K's picture
Thank you much. I wasn't wanting to get fancy by any means, I just wanted to control ten LED's on a pin instead of only one,,,
jklug80's picture
Itis possible but the chip wont supply enough current. You need a transistor or relay and a seperate power source.
Ian_K's picture

Could i have my strip of LED's powered by whatever needed source separately from the board alltogether and stil be able to control it from the board

 

jklug80's picture
Yes a transistor or relay would allow a seperate supply to supply the LEDs and the picaxe, etc would tell the transistor when to turn on the power and when to turn it off
Ian_K's picture
Forigive me Jklug for the questions, and thanks for all of the help so far, but where exactly would i solder/place the legs of the transistor? Would the progam just consist of high to turn and low to turn off?
jklug80's picture
Im not a transistor expert but one pin goes to voltage, the other goes to the + on the LEDs, the third goes to a pin on your PIC. Make sure to read a datasheet for how to wire it up. Also look at any paperwork that came with the LEDs to determine how many batteries you need to light all 10 LEDs at once. It will likely be close to 20 volts!
Ian_K's picture

Thank you much jklug, this whole thing makes a ton more sense to me now! I'm going to experiment with it now. I know you said you're not a transistor expert and probably won't know the answer but would just like a npn transistor work or how would I find out which particular transistor I need?

Ian_K's picture
Well never mind, maybe, assuming Chris the Carpenter is right, I guess I just need a n2222 transsitor
Ian_K's picture

I was merely wanting to have maybe ten (give or take a few, for intensity) standard 5mm red LED's with a voltage of 2, soldered together and soldered to the board, so I could control/program for the entire strip of LED's instead of controlling a single LED from the board. Would something along these lines work:

 http://www.instructables.com/id/SZYBTDHF7DWO46V/

Many comments stated that you need to add resistors but no one quite knew exactly if you should add one big one at the first LED or a small one on every LED. Thank you for the quick response and answering the first part of my question!