Questions regarding Servos and a LiPo.

Other Hardware Motors, Mechanics, Power and CNC
1

Hi there,

I'm currently working on a 6DOF robotic arm, powered by an Arduino (of course!) Uno R3. I built the entire thing a few weeks ago, off a kit I found locally and I realised that the servos that were provided were rubbish and so was the controller (which i was going to replace with the Arduino anyway).

I recently picked up 4 BMS 860D-Max Champion Servos to replace all the crucial joints in the robotic arm, so that they can support the weight with ease.
This is what i got:

Torque At 4.8V: 18.8kg/cm , 258 oz/in
Torque At 6.0V: 23.2kg/cm , 322 oz/in
MOS-FET driver (spirited driver able to push over 7A power)

I've also got to LiPos to choose from:
11.1V 3800mAh Hacker LiPo (3S) and a 7.4 5000mAh Hacker Lipo (2S)

I'm going to be running either of those power sources through this 12A UBEC and then powering the servos with the 6V option on the UBEC.

My questions:
1.My knowledge regarding UBECs is very limited, so I wanted to know if i've chosen the right one, or is 12A too much current to power 6 servos?

2.Which would be a better battery source for this project? The 3S 3800mAh or the 2S 5000mAh?

3.I'm finding it impossible to get hold of EC3 connecters here in India, so I've decided to cut out the banana plugs from one these (that came with the battery/charger) and solder it to the input leads of the UBEC. The input wires to the UBEC seem to be of a much smaller gauge than what the LiPos are generally connected with. Would this be a problem? I've read mixed opinions regarding this so I just wanted to make sure before hooking everything up.

PS: I'm terribly sorry if these questions come off as amateur. I don't have much exposure to electronics in my field of computing. This is one of my first projects that involves a bunch of hardware.

Thank you in advance for your help. Also, if you have any tips for working with this setup feel free to post them here. I'm here to learn!

Cheers,
Shreyas

2

  1. The servos only pull as much amperage as they need, so having a UBEC that is capable of providing more than enough amperage is not an issue. Actually, it's a benefit because you always want to be sure your power supply can provide more current than you expect to need, and these things tend to get rated too optimistically anyway.

  2. Both are about the same. The UBEC is a switching regulator so the input voltage doesn't matter much.

  3. LiPo batteries of the size you have are probably capable of 100A peak output so the battery manufacturer uses heavy wires when building it. The UBEC consumes much less amperage so its manufacturer uses thinner wires. From a safety aspect it wouldn't hurt to put a fuse between the two but that's about it.

3

Chagrin:

  1. The servos only pull as much amperage as they need, so having a UBEC that is capable of providing more than enough amperage is not an issue. Actually, it's a benefit because you always want to be sure your power supply can provide more current than you expect to need, and these things tend to get rated too optimistically anyway.

  2. Both are about the same. The UBEC is a switching regulator so the input voltage doesn't matter much.

  3. LiPo batteries of the size you have are probably capable of 100A peak output so the battery manufacturer uses heavy wires when building it. The UBEC consumes much less amperage so its manufacturer uses thinner wires. From a safety aspect it wouldn't hurt to put a fuse between the two but that's about it.

Thanks a bunch man, I just wanted to make sure everything was good to go before actually wiring it all up. The fuse between the UBEC and LiPo sounds like a great idea. I'm going to go ahead and try that.

Cheers