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Author Topic: 12 volts controlled by 5v (arduino)  (Read 1888 times)
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I am very very new to transistors and im having trouble with them. I have a 12v led module. I want to make a flash pattern from the arduino which ive done with no problem. I have all of the wiring setup. But I cant seem to find a transistor that will get the 12 volts to pass through it. I have it setup so that the 12 volt negative is on the collector, the arduino is on the base, and the negative side of the led is on the emitter. The positive side of the led is hooked up to the positive side of my 12 volt source. Now the led lights up and does the pattern but it is 1/100th of the brightness that it is when its just straight 12 volt. Now ive been running back and forth to radioshack trying to find a resistor that will allow me to get all of the 12 volts though yet be control by a 5 volt source. I bought a 3055t and I wasn't able to get 5 volts to drive it (it wouldnt even light up). I'm using a 2n2222 now but not even close to 12 volts are making its way though it. Any ideas? What should I be looking for in buying a transistor or is my wiring screwed up or something? I'm pretty certain I am just not using the right transistor.
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It's not 100% clear to me from the description how you have that hooked up... pictures are worth 1000s of words, hint hint  smiley-cool

But have a look at this which is for a similar NPN transistor to the 2222... Maybe you don't have it all hooked up this way?
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Hi.
Welcome to the arduino forum.
A simple circuit of the arduino to the transistor and battery connections would help us to help you.
The 3055 is A good choice.
Regards Antony.
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How much current does the 12v LED module take? If it takes 500mA or less, then I would switch it using an NPN transistor, e.g. BC337 or 2N2222. See reply #1 for how to connect it, but reduce the resistor from 1K to 220 ohms. If the module takes more than 500mA, then a logic level mosfet is a better solution (the mosfet will work fine at lower currents too, but costs more than an NPN transistor).
« Last Edit: July 09, 2012, 12:47:32 pm by dc42 » Logged

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More pics, it wont let me put them all in one post.  smiley-cry


* TIP3055.jpg (1928.17 KB, 3264x1840 - viewed 93 times.)
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Heres the power supply


* 12v Power Supply.jpg (2357.49 KB, 3264x1840 - viewed 50 times.)
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heres another shot of the breadboard


* Breadboard.jpg (1963.92 KB, 3264x1840 - viewed 68 times.)
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heres how bright the led is just hooked up straight to the 12v source. as you can see the other configurations dont get anywhere close to powering the led up


* Direct to 12V full brightness.jpg (1764.79 KB, 3264x1840 - viewed 38 times.)
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last post (promise).

here is the info about the resistors


* 2012-07-10_20-19-06_466.jpg (1835.03 KB, 3264x1840 - viewed 44 times.)
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Im dumb. I didnt ground the arduino board to the power source ground. Problem solved  (FACEPALM)
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