Hi everyone, I am very new to not only Arduino, but electronics too.
I have a large project I want to build but am struggling to find someone to help me design the circuitry needed, and am hoping someone can point me in the right direction.
I would like to run, among other things, 6 sets of 5, 3w Luxeon LEDs. I want to run them through pwm pins so that their output can be controlled. The 6 sets will need to be controlled independently of each other. Can anyone tell me what I will need in terms of resistors, transistors etc. Will they need drivers? Where could I get them from? Does anyone know of someone in Sussex, England that could help me, if I paid them, with my whole project?
Looking forward to my first response!!!
Will they need drivers?
Yes, they will need drivers of some kind. The "resistors, transistors, etc" that you mention would make up one kind of driver, while a pre-packaged module would be a different kind of driver. What kind of driver you need will depend rather strongly on what kind of power supply you have available, what your space constraints are, and how efficient you need it to be.
Some possibilities with the 3W luxeons are running a set in series, or in parallel. If in series you need enough voltage for the chain (which depends on what colour they are, reds are about 2V and white about 4V for instance). 5 white LEDs for instance would need 20V plus a margin (so 24V would do) and an appropriate series resistance to set the current.
In parallel the standard 5V is going to be fine, but the current requirements are going to be substantial - you have a total of 30 LEDs each taking about an amp...
Driving high current and or high voltage clearly needs a driver, which can be as simple as a single transistor, darlington or MOSFET for each PWM channel - check out the Arduino tutorials for more.
Great, thank you both for your responses. I have been researching homemade LED setups for Marine tanks. Although not exactly what I want to do the principals the same for the lighting part, to a lesser degree. I came across "Buckpucks" for current stabilizers. Would I be better using 1 large DC transformer, or several smaller ones? Could I run the Buckpucks in parallel on 1 transformer?
Also with the Buckpucks I was thinking about splitting the signal. I want to power 4 LEDs from 1 buckpuck say, but distribute the signal into 2 sets of 2. On the Arduino, set the buckpuck to come on in the morning and at night, but somewhere in the middle send a signal to a relay to switch between the 2 sets of LEDs. It sounds easy in my head but just wanted to check before I start looking down this route!
Thanks again, having this forum here is going to be a lifesaver!
Would I be better using 1 large DC transformer, or several smaller ones?
Yes.
Could I run the Buckpucks in parallel on 1 transformer?
Yes.
I want to power 4 LEDs from 1 buckpuck say,
Check if the buckpuck will handle the current. Yes you could use a relay but why not just switch in the extra LEDs with a transistor.
My lack of understanding could be the problem. I wanted to control the pairs independently, ie, not to be on at the same time, can I use a transistor for this? I assumed it could turn 2 or all 4, but not the pairs seperately. Am I wrong?
Thanks for your response
I wanted to control the pairs independently
If they are to be truly independent you need a buckpuck for each circuit.
If however you want to control a pair, and then switch on another pair to be on at the same time, you could do this through a transistor. This means the secondary pair would be separately controlled but not totally independently controlled.
I want them to be controlled seperately, but at different times of day. I was hoping I could use a relay, midday to switch the control over to the other 2 LEDs and at say midnight, switch it back again. This way I could use 1 buckpuck for 2 sunrise and 2 sunset LEDs. Would this setup be ok, and if not could yo explain why, as I can't see why it wouldn't at the moment. hopefully I wasn't explaining myself properly!?
Yes you can use a relay to alternate what physical set of LEDs you are controlling.
You can also use a transistor in the ground path of each set to enable the set you want on. In that way there are no moving parts and it takes less current.
Great, so I need to read up on transistors. Can you recommend any for this purpose? Am I understanding this right? I can use 2 transistors, 1 on each pair of LEDs. Each transistor will need its own digital pin to control it and then a pwm to control the buckpuck! Sorry for my ignorance!
That's right. There are lots of transistors just make sure they can handle the current you plan for them. Most of the time it boils down to what you can obtain cheaply. You could also use logic level FETs, they would run a bit cooler.
Great, I'll look them up now. Not too fussed about cost at the moment, just want it to work at the best I can get it too! Thanks again Grumpy Mike, BIG help!!!