I had a quick question about the Arduino's output power pins. Is it possible to use the 5V logic power pin to power multiple devices? (such as two IR sensor arrays) If so, how would you do that, and it not, how would you get around it? Thanks for all the help
You don't want to run more than 40 mA through a pin. You can, briefly, before it burns out. It's more usual to keep the load down to 20 mA per pin, less being fine.
Usually the way is to have the pin run something else like a transistor connected to external power (that has a common ground to the Arduino power) to handle more than a led.
I think chimpfunkz refers to the current from the "5V" pin, as opposed to the current from the I/O pins.
You can definitely get two IR sensors (or receivers) going from the "5V" pin.
I was thrown by the word "logic" thrown in. All my "outputs" are 5V.
I think that if you have external power and more than 500 mA total that it's better to not to channel all the power through the Arduino unless it's something liked a Ruggeduino and even then it's better to keep signal to signal, power to power and grounds common. That way the same circuit will do for everyone.
I was referring to the 5V pin. this is confusing me a little, but let me try to understand this by asking a question.
What does the 5V pin do that can't be done by any of the other pins? Is it just a dedicated pin that will only output current, or does it output something special? if it only outputs current, does that mean that I can take another pin, say a digital I/O pin, and use that digital pin as a power source for a second IR sensor? I ask this because I am building a robot that needs to have a motor controller, an IR sensor, and a ultrasonic sensor, and each of those needs a 5V logic power pin.
Another way of asking this would be Can a digital I/O pin complete the same function as the 5V pin?
"5V" is the output of the Arduino on-board 5V regulator.
It is "system power" and has additional capability of powering other ICs, transistors, and so on.
The I/O pins are part of the microcontroller itself.
So if I wanted to use multiple sensors that all required a "5V" input, I'd have to get power from an external source?
Depends how much power, and if you are runnning from USB, or from power going thru the regulator.
USB is limited to 500mA.
Regulator can do more like 800mA, but will shut itself down if the source voltage is too high and it gets too hot.
Best bet is an external 5V wallwart, connect to the 5V pin /Gnd and to your sensors in parallel.
example:
http://www.dipmicro.com/store/DCA-0520
No, you don't. But it's good to remember that power routed -through- the board does go through some board components including traces. A few leds is no problem as a few leds won't pull 400 mA.
"Good Practice" is not the same as "Have To". But you get used to doing things some ways then you might find yourself later on coming up (or not) with tricks to save a flawed basic approach you might have trouble identifying.
As long as I run from USB I "Have To" get my power -through- the board even though the 5V regulator is not part of that path but if I want to work with anything that draws more than half an Amp of 5+V, I will use a plug in or good bit of battery (but battery only if I have no choice) as external power and include power and ground runs straight from external to the power-sucking parts of the circuit, with of course all grounds connected.
Okay, I'm jumping in here a bit late, but I noticed a few things, first of all you are asking if you can run "sensors" off the 5V on the Arduino. I think I got that right. Secondly, you said...
" I ask this because I am building a robot that needs to have a motor controller, an IR sensor, and a ultrasonic sensor, and each of those needs a 5V logic power pin. "
If you are adding all those sensors to your project eventually, you should design it properly, by having those devices have their own power feed. Furthermore, I'm not wanting to be negative, but with all the work ahead of you (with all those sensors), you might want to get a better handle on current loads in your project. Understand that an I/O pin can only 'fan-out' so many ICs.
Besides, what's supplying power to your Arduino? Just take the power directly from that supply. Again, depending on your final current loads for all your devices, this will tell you if you need power transistors in place to assist you.
But, regardless...with that many sensors(devices) keep to good housekeepping practices and do not take the power for the Arduino...it's meant to power other ICs, not devices (okay, maybe a few LEDs).
Hopes this helps...and good luck with you robot. You may want to look at this site.