I am making a project with 8 servo motors sg90 with an arduino uno. The spec sheet shows they are 4.6 - 6v. I have read that for these type of servos I should budget approx. 800 mA to 1A. S I have been looking for an external power supply of 6v with (900 x 8 = 7,200) 7,200 mA. I only seem to find NiMH batteries that go up to around 2,000 (link for similar ones below). It seems like an awful lot of power if I have to use 4 of these in parallel (or 1 of the below batteries for every 2 servos)
Am I working it out all wrong? These batteries are for remote control cars and it would seems strange that my little servos use 4 times more power than those cars that go zipping around.
Check your sources on information, I think you are way over budget, viz:
"The servo runs on 5V with a current draw about 10mA at idle and 100mA to 250mA when being commanded to move depending on how it is being operated. Current draw can get up to a maximum of 360mA under a stall condition."
Thanks alto777, I did research before posting (would bad manners not to) and found comments stating that this servo can draw up to 1A. I think I will go with the manufacturers specs (not that I don't trust forum posts ) .
Another thing to watch out for is startup with multi servos, I always put a 200ms delay between attaches so they don't all pull stall current at the same time.
servo1.attach(pin9);
delay(200);
servo2.attach(pin10);
delay(200);
// etc.
I am making a project with 8 servo motors sg90 with an arduino uno. The spec sheet shows they are 4.6 - 6v. I have read that for these type of servos I should budget approx. 800 mA to 1A. S I have been looking for an external power supply of 6v with (900 x 8 = 7,200) 7,200 mA. I only seem to find NiMH batteries that go up to around 2,000 (link for similar ones below). It seems like an awful lot of power if I have to use 4 of these in parallel (or 1 of the below batteries for every 2 servos)
Am I working it out all wrong? These batteries are for remote control cars and it would seems strange that my little servos use 4 times more power than those cars that go zipping around.
The question that first comes to mind is, are all the servos working at the same time?
i.e. are some stationary while maybe one or two are moving..?
Use the 1A demand previously stated and work out battery charge life from there.
Also as previously pointed out, 2000mAh is the battery capacity.
So roughly 200mA for 10 hours although in real life this has to be derated perhaps 50% as the mAh rating is at a low rate of perhaps 100mA or so.
Battery university web site will show you a graph of this.
) .