I read now that i should not power up multiple servos at a time from the 5v pin. i did allready while testing animation cycles. but for longer terms i need an alternative, i wont ruin my board
now i'm unsure how i can power the board and the servos, at worst all at the same time... or at least 2 at the same time for a longer time.
i thought about 9v block battery or 4xAAA for the board and another one for the servos, but i'm not sure if i burn the servos with directly 9 or 6v directly connected if the quadruped runs for several minutes.
i heard some rumors (some say yes some say no..) that i shouldn't connect the 9v directly to the VIN and GND for long time, and that i have to reduce the 6/9 V down to 5V for the servos...
it would be great if i can power board and servos with only one 4xAAA pack or one 9V Block battery on the VIN/GND and the Servos directly. But something tells me this wont work...
sry if this question is stupid, but i was allways bad at electronics and more in programming, but thats what i wanna improve
You need something more than 4 AAA batteries. You need to plan for 1 Amp per servo, at the voltage that the servos are designed for. For 12 to 18 servos, that's a very beefy power supply.
cybeaer:
I read now that i should not power up multiple servos at a time from the 5v pin.
You shouldn't even power onetiple servos that way
1A is as PaulS said a useful rule of thumb, since very few sites quote any figures for servo current. That said, this site quotes 650±80mA for yours at stall, so 730mA, and that's actually a mere micro servo.
I think that the best choice would be using a 7,4V lipo battery for your project, around 2000 mah. If you have never used one, search about this type of battery before, they can be dangerous but is the most common type of battery to projects like yours.
jremington:
Many servos are destroyed by using a 7.4 V power supply.
I meant to say that too in my post above yours ;). Surely the best supply for a whole lot of servos is whatever they use in RC models, since those are presumably designed for servo operation?
The Arduino has a linear regulator so when you're connecting 9V and regulating it down to 5V it's spewing out 4V (multiplied by the current being used) as heat. So depending on what you have connected to the Arduino's 5V power it could be a lot of heat being generated or not a problem at all, but if you go over ~250ma of current then that's (4V * 250ma) 1W of heat and that starts to be a problem.
By comparison, a switching regulator is always around 90% efficient no matter what the input voltage is. Not only do you waste a lot less power but you don't have to worry about your regulator getting too hot.
In the RC world you will find switching regulators sold as an "SBEC" or "UBEC".
So this would be the part that gets hot if i pull 12A from 4xAA through this?
-- edit --
i've just seen this have a max output of 3A, if i understand some datasheets the usage is from 16mA (idle) over 270mA (no load) to 730mA (full load). And the batteries should deliver some about 1000 to 2500mA.
If i move only one leg (3 servos) active and 9 servos at idle at a time (2334mA) i should slightly below the limit with fresh loaded batteries.
the question is now what happens if the batteries deliever to less ampere to the servos? heating up the step-down? slowing down the servos or with less strenght?
The LM2596 is a switching regulator, and it will get hot but not hot like a linear regulator when used in similar circumstances. If you think you're going to need more current the easy solution is to use more than one and split them up between the servos.
If the batteries cannot supply enough current then you'll find your robot starts to get twitchy. The Arduino might brownout and reset, stuff like that.
Lastly, battery capacity is typically rated for a 10-hour timespan. A 2200mAh alkaline battery will only provide that total 2200mAh if you draw less than 220ma from it. So you get less total capacity if you draw too much current. Lithium batteries handle high current draw much better by comparison.
the arduiono and all parts beside the servos have an own battery, like on some other projects with a 9v block battery.
could the arduino brownout and reset if only to less current for the servos?
btw what to you mean with brownout?
but a 2nd battery pack for the servos with own step down is a idea, i just have to look for the weight, because its allready near 300g, and i dont know exactly how to calculate how much the servos can lift, but with arms about 5cm it should a whole weight about 350g i think... maybe complete wrong
Or if i use 3xAA with about 2500mA (thats written on my accu batteries) and 4,5V without step down...
the batteries i use are recharchables anyway, so the bot dont have to run 10h with one charge, maybe one or two hours would be great ^^
i'm working on the gait for my quadruped and it seems the 2500mA from the akku's really wont be enough
isn't there a safer method for getting more mA? Beside LiPo's?
Something that wont explode or catch fire easily...
I heard 18650 akkus are not really safe too, and have a "huge" urge for controlling circuits.
So basically same as the LiPo's.. And getting more AA in row and paralell would be a too heavy package...
The Bot have to run without watching, even no one is at home for example..
Fear of 18650 cells is unnecessary. Every modern cordless power tool contains them, for example. They're quite likely the most common form of Lithium cell there is.
If you're looking for extra safety you can look for "protected" cells; they contain a small circuit board that will prevent overcharge/overcurrent/overdischarge/etc.
i got my wiring for my bot done with normal battieries (for first try)
i deliver the power vrom 4xAA through an LM2596 DC-DC... The Servos connect each a +, - and a D2-13 port of my wiring.
Problem is now, the check led lights up when nothing is connected to the LM2596, but as soon as i connect the cables to my board it wont lit and getting way to hot in less than 10sec.
i checked the wires without power with an voltmeter and it tells me there is a shortcut betwenn + and - of the servo pins... the servos work if powered single by an arduino directly. do the servos connect the ports directly? and can this shortcut the step down module?
even if i connect the out wires of the LM2596 to an servo and the data pin to an arduino, the servo wont move, if i power it directly from the 5V port of the arduino it moves...
Can someone point me to my error?
if this is fixed i wanna change the power source to a lipo or an 16850 battery, so can someone point me site where i can get information how to handle and use this things, what i need for such batteries...
And does someone maybe have a tip for a good lipo/16850 battery/set?