since i've apparently already fried one board i thought it might be prudent to pose a couple of questions before i do it again... the basic setup is fairly straightforward - a stand-alone board with an IR receiver and a servo (cont. rotational hitec 4.8-6v)... easy-peasy...
can i power the entire thing with a single battery pack or do i need separate power for the servo?.. obviously i prefer to have a single source (9v?.. 4aa?.. 8aa?..) and i'm trying to wrap my head around this stuff as i learn... baby steps...
i already learned that i'll need common ground between the board and the servo... but what else?.. please let me know if i left out any critical details... and if one of you experts can walk me through the hook up as if i were a slightly slow 10 year old, i wouldn't get offended... just please don't condescend - as i said, it's a learning processes for a lot of us here
again, i’m in uncharted waters here so please constructive criticism only
my goal is to operate the entire project with a battery pack… i’d like to use a single 4aa pack or 9v (i’m reading a lot about 9v draining super fast so maybe not the best solution)… if not those, then 8aa?.. although that’s way too many for my taste… my “understanding” of electrical circuits in general and arduino in particular is rudimentary at best… but i’m learning… so, anyway, can this be accomplished?.. i mean, i’m sure it can but am i on the right path?.. thanks for all the input, comments, corrections, etc!..
You could use 8 rechargeable AA batteries (1.2v each) for a `9.6v power supply. Connect this to the arduino vin thru a small diode, and put a large capacitor between the arduino 5v pin and the arduino ground pin. The capacitor and diode will help protect the arduino from low voltage conditions when the servo moves. For the servo power, you can use a 7805 voltage regulator chip and diode like below to supply the servo with 5.7v from the 9.6v battery pack.
You will want a 5V regulator if you are indeed building your own Arduino clone. You'll need a 5V or 6V regulator for the servos. You could run the whole thing off a single 5V regulator, but you'll need to make sure you have one that will handle the amps for both the Arduino and the servos. If you have big, beefy servos, and lots of em, a single 7805 might not cut it.
I have done a circuit where I had an Arduino controlling the servos but had separate power going to the servos. It wasn't battery powered, but it worked fine.
My custom RC ship transmitter has 8 AA batteries (12V) which is well within the UNO's regulator range.
I have a robot that is powered by an UNO and a 11.1V 3S LiPo battery and has 2 on-board servo motors. The servos are powered directly from the Arduino's 5V regulator. It worked fine until I added 5 IR sensors. Now the current load causes the polyfuse to constantly reset the Arduino... Because I'm pulling way too much currrent. I plan to move the servo power off the Arduino and supply it instead from a UBEC I have lying around. The UBEC is essentially a voltage regulator. Of course I could also just wire up a 7805 with 2 caps and get 5V to the servos that way.
Don't attempt to power the servos with more than 6V or you will likely smoke them -- unless the servo is specifically rated to take that kind of voltage. Most are not.
If you do decide to run the project from 4 AA cells then there is no reason not to just power the servo directly from the battery pack. R/C servos were designed to work from standard 4 AA cells. That is why the most standard voltage range quoted for R/C servos is 4.8 to 6vdc, the normal value of most 4 AA battery packs used in R/C flight packs. Regulating servo power gains little value and usually just wastes battery duration unless a switching regulator is used.
guys, you all rock!.. seriously... thank you for all the awesome and thoughtful advice!..
i wish i could say that i understand it all... or even most of it... alas, i'm way too green in this area to "get it"... now i really need to roll up my sleeves and decipher the different suggestions (how many way can one skin a cat?)... and then figure out what makes sense for my project... maybe it'll help if i describe it:
a very simple drawer with a doggie dish that slides out of its cabinet (approximately 6-7 inch travel) when i click my remote... and then slides back into closed position the same distance when i click another button... so that's what needs to be powered - ir receiver, servo, arduino...
for this setup i genuinely suspect that my needs are so lightweight that i can get away with simple 4aa pack through vin pin... agai, please be patient if it sounds like i'm ignoring a suggestion already provided - i probably just didn't understand it in its entirety... thank you all again!..
What's that transistor doing? It almost looks as if you have connected it between the positive and negative rails.
There are a couple of resistors that I don't understand. One of them appears to be connected as a pull-up for the switch. Any reason against using the internal pullup instead? The other appears to be connected to nothing - but maybe I'm just misreading the picture.
