Hello,
I am pulling parts together and looking for some help, i have a ssc-32 and 24 mg996r to power now i have read that the mg996r have a runnig current of 500 to 900 mA so potential 12 servos = 3 legs thats 10 to 12 amps pulling?
Now that said i have a 4s lipo so 14.8v 4500mah 45c can i run this to the ssc-32 or do i need a dc to dc regulator and if so what one would i need to get?
Also for test periods whats the best mains supply?
@RickyBurton Like you said, according to the manufacturer, the mg996r is power hungry, with 170mA no load operation and up to 1.4A at stall. Since TowerPro doesn’t have a current vs. Torque curve, you can “guesstimate” that 0.9A will provide 0.9/1.4 = 64% of the stall torque. If you have all servos operating simultaneously at that current, yes, your power supply will need to be able to provide 24x 0.9A = 21.6A . You didn’t say anything about the project, but you did indicate “walking”, so we’ll assume it’s a legged robot? You talked about a 4DoF hexapod in another post, so if we assume that’s the case here, then no, most walking gaits will not have all servos requiring high current.
As an example, the Lynxmotion T-Hex 24 uses the SSC-32U: https://www.robotshop.com/en/lynxmotion-t-hex-4dof-hexapod-robot-kit-no-electronics.html
When walking, the six servos in the base don’t draw much current since there’s minimal resistance. The resistance would increase if the robot was walking up an incline though. The power needed to lift a leg is significantly less than what’s needed to lift the body, so less current draw from all of those servos as well. If you use a tripod gait, that means 18 out of 24 servos are not consuming “much” current, while the others are under stress to keep the body raised. This having been said, the mg996r consume more current than the Hitec 645MG which are used in the T-Hex.
So to your questions:
It will depend on the weight of your hexapod, the walking gait etc. If in doubt, the SSC-32 and 32U servo power can be split between two batteries (one battery per side) which reduces the current draw from each battery pack. Be sure to remove the jumpers.
The mg995r operates at 4.8V to 6.6V, so a 14.8V pack is really far from optimal and you should really consider either a 6V NiMh pack (check discharge current though), or a 7.4V LiPo and a high current regulator with 6V output. Is there any reason why you would want to use a 14.8V pack or is it just something you have already (so don’t need to spend on a new pack)? The main pack should ideally be selected for what’s drawing the most current, which in the case of a legged robot, is the actuators, and as such, should be 6V.
You’d need a 6V wall adapter (or two) which can provide pretty high current. If you’re not sure, two of these might help:
