I want to control several (undecided) cut strips of these led lights:here.
I want to be able to turn the LEDs on and off from the arduino, but I know that the voltage is too high to work with with the arduino and I don't want to fry my arduino. I've looked into relay modules, but I'm a software guy and I don't understand even the difference between voltage and amperage (I think I have the idea down, but I get the two mixed up sometimes). I also don't know how much voltage or amperage I should be giving each strip or how to control that. I have all my code set up to control my arduino with my simple C# form I've made, but I'm dumbfounded when it comes to hardware, can anyone help?
Also, I'm not well into money so I'd like to avoid spending money on some relays if possible.
Do you want to be able to drive each LED individually? Because it's not possible with this strip.
If you search a little on google you will find that one meter of these LED strips, will use approximatively 5W.
You have a formula:
P (Watts) = U (Volts) * I (Amperes)
So I = P / U = 5W / 12V = 0.42 A for one meter. That strip is 5 meters, so for each strip that you want to buy, you need a 12V power supply that can deliver at least ((0.42 * 5) + safety margin) = 2.5A (2500 mA). For 2 strips, you need a 5A power supply, etc.
This is a lot of current and as you said, you will need relays. you can find relay modules for about 2$ on ebay
You can also use high power transistors instead of relays. For example, the TIP120 (one for each strip).
Hi, I would not reccomend relays for led strips. They are bulky, noisy, they wear out, cannot be driven by Arduino pins directly and cannot be used for fading or colour mixing (with rgb strips).
Power fets are a much better option. Examples are irl520 or stp36nf06l. Make sure the model you choose have logic-level gates. Use 10K resistors to pull the gates down to ground to prevent problems when the Arduino starts up.
Do you want to be able to drive each LED individually? Because it's not possible with this strip.
If you search a little on google you will find that one meter of these LED strips, will use approximatively 5W.
You have a formula:
P (Watts) = U (Volts) * I (Amperes)
So I = P / U = 5W / 12V = 0.42 A for one meter. That strip is 5 meters, so for each strip that you want to buy, you need a 12V power supply that can deliver at least ((0.42 * 5) + safety margin) = 2.5A (2500 mA). For 2 strips, you need a 5A power supply, etc.
This is a lot of current and as you said, you will need relays. you can find relay modules for about 2$ on ebay
You can also use high power transistors instead of relays. For example, the TIP120 (one for each strip).
@guix thank you so much for this helpful information! but I have one other question, you said I'd need 0.42 A for one meter, if I simply wanted to power three LEDs out of the strip, how would I calculate how much power to give it?
Well there are 300 LEDs on a 5m strip, so 60 LEDs per meter, so 3 LEDs will "pull" a current of approximatively (0.42/60)*3 = 0.021A = 21mA.
You don't "give power" to a device, instead you allow the device to "pull" current out of a power supply. That's why you need a power supply that can deliver at least enough current required by the device. If your power supply can't deliver enough current to the device, the power supply (or at least the fuse, if there is one) will fry
Like in your house, when you connect too much powerful devices on one line, the circuit breaker will be triggered to protect cables from overheating and burning your house..!
guix:
Well there are 300 LEDs on a 5m strip, so 60 LEDs per meter, so 3 LEDs will "pull" a current of approximatively (0.42/60)*3 = 0.021A = 21mA.
You don't "give power" to a device, instead you allow the device to "pull" current out of a power supply. That's why you need a power supply that can deliver at least enough current required by the device. If your power supply can't deliver enough current to the device, the power supply will fry
sorry, again with the questions but you've just been a lot of help as opposed to everyone else; I have a 12V 5A D/C adapter which obviously has a V+ and V- wire. would there be any consequence to wiring all my transistors to one adapter? and I have the standard breadboard that my arduino came with, could I place my transistors and use my 12V adapter for its live and ground?
You can connect all your transistors to one power supply of course, and yes you can use 12V on a breadboard, no problem.
If you want to connect only 3 LEDs per transitor, you don't even need high power transistors.
About your picture: I don't really know... because I don't know if the LEDs that are used in this strip, are common anode or common cathode. Also, you should put a resistor (1 KOhms is frequently used) between the arduino and the transistor base, and maybe a common ground with the arduino. To be honest, I don't know enough about transistors to really help you about that
guix:
You can connect all your transistors to one power supply of course, and yes you can use 12V on a breadboard, no problem.
If you want to connect only 3 LEDs per transitor, you don't even need high power transistors.
About your picture: I don't really know... because I don't know if the LEDs that are used in this strip, are common anode or common cathode. Also, you should put a resistor (1 KOhms is frequently used) between the arduino and the transistor base, and maybe a common ground with the arduino. To be honest, I don't know enough about transistors to really help you about that
Good luck!
thank you so much for your help, I'm now much more confident to start my build. thank you very much and have a great day!
PaulRB:
As the only other person who has responded to this thread, "everyone else" must refer to me:
I had only intended to be helpful. Perhaps you could explain to me how I failed so badly?
I am so sorry, I should have clarified, I posted this question on a few other boards in order to get a variety of answers. Your answer was helpful and informative and I wasn't directing that statement towards you in any way. I'm super sorry, please have a nice day!
I am a newbie too, trying to do a similar project ( motion detected accent lighting on stairs ). The following article was very useful for me, thought i'd share it.
