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Topic: powering led strip through arduino (Read 355 times) previous topic - next topic

cpelech

OK! I've been using capsense to turn on LEDs. Based on the capacitance reading the LEDs are giving an increased voltage. So its basically a proximity sensor that has LEDs brighten as you get closer and then brightest when touching the sensor. It works well and I've been using a 12V DC 800mA adaptor to power it. I bought LED strips thinking I could put them in the bread board and they would work like the regular LEDs I've been using in parallel. This is not the case. I bought these http://www.amazon.com/gp/aw/d/B002QQ1YOM when I plug the adaptor into the female plug it came with the lights turn on but when I plug them (I tried all then just 3) nothing happens. What am I missing? Thanks

DVDdoug

#1
Aug 21, 2013, 01:08 am Last Edit: Aug 21, 2013, 01:10 am by DVDdoug Reason: 1
It would REALLY HELP to have the specs on that thing...  Voltage & current (milliamps) rating, or the per-foot ratings, etc.   When you buy something like that and the seller doesn't provide the specs, it's a good idea to look elsewhere, or get the manufacturer's part number so you can find the data sheet.

An Arduino puts-out 5V at a maximum of 40mA.   That's only enough to power a few LEDs, depending on how they are wired and how much current per LED you "allow" (depending on the series resistor).  A "typical" LED is rated for 2V and 20mA.    It's not enough to directly power many LEDs.   (Of course, with the right electronics you can control anything...  I've got an Arduino-controlled lighting effect that runs 800W of colored floodlights.)

To power an LED strip, you'll need a MOSFET (or transistor) to boost the current.  I found somethng that says your LED strip requires 12V.    Since you have a 12V power supply, your MOSFET/transistor (driven by the Arduino's 5V output) can control the 12V at higher current into an LED strip.

If your LED strip requires more than 800mA (which it might), you'll need a bigger power supply.

CrossRoads

Strips like that are typically 3 LEDs in series with a current limit resistor drawing 20mA from a 12-14V source. All the 3 LED sections are wired in parallel, the 12V/Gnd is passed along from strip to strip.
So you need an N-channel MOSFET or an NPN transistor, connect the + of the strip to +12V, the - to the NPN collecter, the NPN emitter to Gnd, and an arduino pin to 250 ohm resistor to NPN base (the N-channel equivalent pins).
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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