Let's Make Robots!

how do I determine power requirements for an 18 towerpro mg955 servo hexapod?

I recently bought a Chinese made hexapod and 32 servo Torobot controller.  Hooking up the bluetooth module to the controller was easy, and so was connecting all 18 hexapod servos, and the programming looks straightforward.

the servos are towerpro mg955.  I have found various info on these (including comments re their quality) but was not able to find out anything about how much current they can use/need under load

I am not worried about the power supply for the servo controller (which works fine), but the 6v 2a supply (wall wart) I am using for the servos seems to be inadequate (servos become spastic/disfunctional when I try to connect and move more than 6 or 7 servos).  that tells me I need more power for the servos.

does anyone know how much current one of these servos uses under load?

also, what battery would I use once I want the hexapod to run without connecting to a wall power supply?

any help appreciated (and sorry if this should be in the newbie forum)

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

thats a heck of a lot of amps.  maybe I should wait for the Mr Fusion reactor from BTTF to power it.  wow.  thx

Until they invent Mr. Fusion I suggest using a 7.2V NiMh or 7.4V LiPo with a storage capacity of at least 4500mAh. You will also need 20A automotive wire to handle the power and a switch that can handle the same DC current. Remember that 20A will be your approximate peak current. The average current draw might only be 5A depending on the robots action. You must allow for peak currents otherwise your robot can suffer from "brown outs" which can cause your MCU to reset unexpectedly.

here is a pic of the robot on ebay.  shows you details on the legs etc.    http://www.ebay.com/itm/160797464275

What voltage would the nimh battery pack be? If its 5-6V you can power the servos without a voltage regulator (UBEC). If it's higher you will need a very powerful vreg like an UBEC. I'm not even sure if my 8A UBEC will handle all the servos.

If I may ask, could you take some sharp detailed pics of one of the legs of your hexapod? I'm going to design my own in Solidworks but could use a reference :)

    

Ah, I assume you have bought this hexapod? http://www.goodluckbuy.com/arduino-alumin-hexapod-spider-six-3dof-legs-robot-with-18-servos-32-channel-servo-controller-board.html

I'm planning to built my own hexapod and have bought 30 MG996R servos (which are similar to the 995) and the same Torobot controller. I will be using an 8A UBEC and a big Lipo battery (4-5000mAh) to power the servos. I'm not 100% sure but I think those MG995 servos draw about 0,5A under load. A 2A power supply is certainly to weak for those servos.

same robot, different supplier.  I got mine for $299 (US) including shipping, but it didnt include the servo controller.  it was hard to pass that deal up (even tho I had seen some concerns re the servos) since I am just starting to get back into electronics/etc and didnt want to spend too much

thx for info re 0.5a under load.  I definitely need lots more power. I was going to avoid the lipo batteries for now; sounds like they need to be treated with kids gloves re discharging/charging etc, and was going to look at some nimh cells.

if I go for nimh batteries, do I need something to protect the servos and controller? something similar to the UBEC?