So I have a project in which I am using 4 Towerpro MG996R servos under fairly High Load (only one at a time for a few seconds)....
I first tested the servos with 4 AA batteries in series which works fine (an example of the circuit I used is attached although the voltage says 4V which is obviously wrong)! The project needs to be run off mains power so i brought a 5 Volt, 3 Amp mains adapter thinking that it would have plenty of power however when i wired it up to just 1 servo it couldn't handle it (let alone 4).... the servo rotates ok (under no load) but when it gets to its destination it twitches and sometimes it starts its movement is a bit weird as well (the led on the plug also switches off when the servo is moving).... I assume this is because it cant draw enough current/voltage from the plug? What can I do to fix this?
I have looked at adding a capacitor... Would this help? Where should I add it? What value should it be?
I have researched it online and all the posts I have found suggested that replacing the batteries with the adapter should work fine... but it doesn't
Did you try measuring the stall current when powered from batteries?
One approach is to use batteries that are trickle-charged from the mains,
however its tricky to get right (avoiding over-charge yet providing enough
power).
Capacitor would have to be large. Capable of supplying several joules, probably
over 10,000uF, but the only way to be sure is try it, start at 1,000uF and see if
that helps? If you are lucky the supply is only objecting to current spikes and
a smaller capacitor will do a lot to help with that.
MarkT:
Did you try measuring the stall current when powered from batteries?
...
Capacitor would have to be large. Capable of supplying several joules, probably
over 10,000uF, but the only way to be sure is try it, start at 1,000uF and see if
that helps? If you are lucky the supply is only objecting to current spikes and
a smaller capacitor will do a lot to help with that.
No I am picking up my multimeter tomorrow so will have a test then!
If i was to connect a Capacitor where abouts should it be connected?
You might also want to use an inductor in a Pi circuit like the last one on this page. Use as big an inductor in terms of inductance not size as you can get that will handel the current. http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
I have built a hexapod with 18 MG996R servos. These servos can pull +1A under heavy load. I powered them from a big 3S LIPO battery and several big UBEC's to drop the voltage to 6V. The MG996R servos have a bit more torque @ 6V then @ 5V. If you feed them less then 5V they will lose a lot of torque.
