I would be grateful of some help with an Arduino/5 metre LED strip that I have setup in my kitchen. I have setup the project so that when I walk within 1 metre of my kitchen surface LEDs are triggered. After 2/3 days of having it running it stopped working so I used a multimeter to test the power output from a 12V 1000mA power cable that I'd soldered in to my project and it read no voltage. Presume the fuse has blown.
Tip120 to control power to lights from the Arduino
This is my first foray into electronics and Arduino and I have wired it up with prototype board using the attached wiring diagram. The diagram doesn't account for the sensor but I'm presuming that it is not the root of my problems. I should also note that I'm powering the Arduino via the VIN pin and drawing current directly from the 12V power output; sharing this with the power that goes to the LEDs.
After some reading I am presuming that my issue is with the fact that I am only supplying 1000mA and this has blown the fuse. Should I be supplying nearer 2000mA to 3000mA? I was not fully aware of the impact of amps on this when I planned this project - I only considered voltage so if this seems like a 'schoolboy error' than I accept that. I would be grateful if someone could validate my thoughts or shed any light as to my wrongdoings! Thanks in advance.
There should be a (~2K) resistor between the Arduino and the base of the transistor. Without it you have no limit to the current flowing from the Arduino pin (its max limit is 40ma) and this will destroy the pin or the entire chip. You'll want to test that pin to see if it's still functional.
The gain (hFE) of a TIP120 resistor is 1000, so you only need 1ma to the gate to get 1000ma of current.
I don't know what fuse you're describing. If it's the polyfuse on the Uno, that fuse should automatically reset after power is removed.
Thanks for the reply. I'll be sure to add the resistor in.
I was referring to the fuse in the power plug. The Uno is fine but when I put my multimeter on the red and black cables from the power supply it was showing no voltage.
Usually, the only fuse you will find in a modern Switch-mode power supply is the one in the primary (120-230V input) and that only blows if some of the parts in the power supply fail in a catastrophic way e.g. - replacing the fuse will only blow the new one too, and maybe set fire to your house.
You can probably safely short a modern power supply, and it just shuts down to protect itself, recovering when the short is removed again. But overloading one, will result in some of the parts overheating, and dying shortly.
Replace the power supply with one powerfull enough to power your LED-strip + 20% extra - you'll never want to run a power supply at it's 100% limit.
1: Replace transistor, you've probably damaged the one you're using right now.
2: Put a 2K2 resistor between the Base of the transistor and the Arduino-pin.
3: Use a power supply capable of delivering 2 Amps or more (more is always better) - A power supply loaded up to it's max will have a shorter life time, than using, say a 3 Amp-model to supply 2 Amps all the time.
Zapro:
1: Replace transistor, you've probably damaged the one you're using right now.
That's unlikely. Without the series resistor, the Arduino will have put excess current into the transistor base, but less than 100mA - which is not enough to damage the transistor, but possibly enough to damage the Arduino pin.
