Servo Power

[DrEvil]

I'm new to electronics, my background is in programming. I'm purchasing 12 HS-485HB servos for a quadraped robotics project, and I have no idea how to power them. The servo specs are:

HS-485HB servo:
Size = Standard
Servo Erector Set = ASB-xx Standard Scale line
Range = 180°
Voltage = 4.8 - 6.0vdc
Torque = 83 oz.-in.
Weight = 1.59 oz.
Speed = 0.18s / 60 degrees

From what I understand, I can use a 6 volt battery pack for power. However, I assume that one battery pack will not power 12 servos for very long.

So, do I purchase multiple battery packs, and bog down my robot with weight? Or, is there a simpler way that I am overlooking?

Thank you for your help.

[Soeren]

Hi,

From what I understand, I can use a 6 volt battery pack for power. However, I assume that one battery pack will not power 12 servos for very long.

So, do I purchase multiple battery packs, and bog down my robot with weight? Or, is there a simpler way that I am overlooking?

Batteries come ind different capacity ratings (mAh) and if you choose the right one, only one should be needed (and this will give the lowest weight per mAh).
You have to select it after the run time you want and buying 2 (or 3) you can just swap in a fresh one when needed, provided you have a fast charger.

Find the average current drain per servo (it depends on how much of the time each of them is run) and decide on a runtime - add 20..30%, as capacity goes down over time.

[DrEvil]

Thank you for the help.

The Running Current of the servo is:
200mA/60* at no load, ~6v

The stall current is:
1200mA, at 6v.

The battery I'm looking into purchasing is a 6.0vdc Ni-MH 2800mAh battery pack.
I plan to purchase two of them, with a recharger.

I also have decided to switch to 8 servos instead of 12, as I am quickly running out of money.

For runtime, I'm hoping for at least 5 mins, 10 is better.

[Soeren]

Hi,

The Running Current of the servo is:
200mA/60* at no load, ~6v

Not sure what you mean by "200mA/60*"?
ServoCity claim 8.8mA/idle and 180mA no load operating
But that's not the entire story. They're gonna be working under load using more current, but OTOH they aren't gonna operate 100'% of the time.

The stall current is:
1200mA, at 6v.

This isn't very important for calculating battery run time, as they shouldn't be continually run when stalled (which is when the rotor is blocked, either by external stuff or bu the internal end stops.

The battery I'm looking into purchasing is a 6.0vdc Ni-MH 2800mAh battery pack.
I plan to purchase two of them, with a recharger.

2800mAh will be less than 2800mAh in your situation. Battery capacity is based on a 5 hour discharge (20h for lead-acid) and the faster the discharge, the lower the capacity.

Shooting for 10 minutes of runtime, calculating with around 1500mAh (depends a lot on the quality of the battery cell), will enable a current draw of ~9A if the cells are up for it. This means that the 8 servos can each use around 1.1A with 200mA left for other stuff (controller etc.) and I'd think your average consumption would more likely be around 500..700mA a piece on average - so I'd assume 15..20mins should be attainable, even if you're the only one who can find the current demand in your application.