Hello everyone im fairly new to the Arduino, i made a post in which i want to use the Arduino to light up a few set of leds. But like i sayd im fairly new and dont understand too much but im willing to learn, i know the basic but if someone could post in the simplested way a solution to this project that i have in mind.
These LED are fairly powerfull and bright so they require a lot of amps,im talking about 1amp each at 3.5v, i have about 6 of them that i want to make into a strobe light system with patterns.
Now i had asked a few memebers they way i wanted to install the LED's with the Arduino,but they tell me that it will cause the Arduino to burnout because of the high voltage.
My question is there a way that i can use the Arduino to run a sequence or pattern in a safe way that wont destroy the Arduino in the process ? liike relays? or maybe something a lot better like almost stright from arduino.
Driving relays also requires additional transistors and protective diodes, as the arduino can only source about 40mA per pin. For high current applications you can use a darlington transistor like TIP120 (60V/5A). It cost about 40c each. It's current gain is about 1000, so if you feed it with 5mA base current, you'll get about 5A of collector/emitter current. So just add a 1k resistor at the base and connect that to a digital output pin.
To get the right voltage for your high power leds, it would be best to get a switching voltage regulator to reduce the 12V to say 5V or so. You can of course use only resistors like for normal leds, but they will get H O T (10W power rating should work at 1A/7V voltage drop).
Thank you for the information I will try and but the information that you gave into use but there is 1 problem,I didn't understand much of it, could you explain in a much simple way,
I understand the I need transistors for the output but is there a another way that I this could be explained, I'm sorry I am just starting with the arduino and very excited to learn so if its possible to bare with me thanks again.
hey madworm and wierdo i think i got it, i read the site that you listed and just reading the first couple of pharagraphs i think i got it
right now im at work and am texting from my phone but when i get home 2night i will draw out a diagram and could you guys tell me if i got it or not? well again thanks for the huge help and i hope i got this
I would use 2 but have a separate 1K from the base of each transistor to the Arduino pin.
Also you can't use a 550R resistor as that would only give you 0.02A through each LED, to get 1A you have to use 12R.
Check that you LED does actually need a current limiting resistor because some of the high power ones have one already included.
im a little confused when you sayd you would use 2
You gave two schematics 1 and 2.
I would use the second (number 2) the one with a transistor for each LED. Trying to get a transistor to switch many amps is not funny and you would be better off using a FET.
Hey I have yet another problem, I don't know how to power up these cree led's but I asked in another forum hidplanet.com and they told me you can't just add resistors like a normal led that I need a certin ship and a lot of stuff that I didn't understand,
but do any of u guys know how to power up these cree, if possible could you explain in the simplest way, I'm kinda embiresed to ask in the other forum since they explained to me a couple of times and I yet don't get it : ( if you guys want I can post what they had sayd
basically the highlights where im confused is that azdave says i cant just use a resistor to power up the led,and that i need a drive and current regulating, and a switching circuit
and thats just to light the led properly, i wanted to use the arduino but by what he's saying it doesnt seem like i can,
also another_person (at the bottom) sayd that i could use a sho-me flasher, thats where i got all confuced because i think its the opposite of that azdave says.
If you could take a look at the forum and maybe break down the steps to me in the simplest of ways (kinda new at this), iv included the sites to the chip and the forum so you dont have to be running around, but like i sayd thanks alot for your help
I couldn't get on that forum because I needed to register, but I have done some digging about and I think I know what they are talking about.
Basically you can use resistors to limit the current but this burns off the excess power in heat. Normally with a few mA of current this is not a problem but here there are several watts of power to get rid of.
Also the actual value of the resister needs to be finely adjusted to get the right current. Again because you are playing with large currents and so low resistor values this is tricky. They just don't make say a 12.5 ohm resistor at ten watts, and you would need a large heat sink or forced air cooling.
So to get round this you can use a constant current regulator, this gets round the resistor value but still has the problem that the excess power is burned off meaning the regulating device will get hot and need a large heat sink and possibly a fan.
Therefore the most power efficient solution is to use a switching regulator. This turns the power on for long enough to build up to the correct value then turns it off. As the current drops it turns it on again, and so on.
In that way little waste power is burned off because the device switching is either on (high current low voltage drop) or off (no current high voltage drop). Therefore the power dissipated by the switching device (power = current times voltage drop) is small.
One popular device is the LM3402. I assume that a "sho-me flasher" is just a built up one of these.
What ever the solution you can still control it with an Arduino, using the LM3402 you can switch it or dim it using a digital pot.
thanks again.
