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Topic: Powering 18 servos (Read 385 times) previous topic - next topic

iii2

Jun 03, 2016, 12:19 am Last Edit: Jun 03, 2016, 12:24 am by iii2
Hi,
Im comeptitng in the robocup competition.
My robot has an arduino mega with 18 servos (power HD 1501 mg) currently connected using a simple 3pins card (not arduino/servo designed)

edit - of course the battery is connected fine, with the + -, this is just a simple sketch.

All of the servos has worked fine simultinasly using a wired PSU , but recently my teacher connected the card to a 8v battery instead and 5 of the servos got fried. the others servo has worked, but I don't want to get this risk again. (I must use battery in this competition)

Could you suggest me how to connect all of this servos to a 8v lithium battery, and to the arduino? (I don't have time to buy a servo sheild, and besides, except of the power issue, the servos works fine).
In addition, will a capacitor or a resistor in the servo circuit would help?
I want the servos to work without jitters, and make sure they get to their desire positions.

Just for you to understand what kind of servos usage I have - https://youtu.be/I3efRcslXBw?t=190
(this is not my robot, but it's very simillar, they both usu arduino and has a battery to control the servos).

SurferTim

Get a Battery Eliminator Circuit (BEC). You can Google it.

MarkT

You'll need a substantial DC-DC converter for that, you might be peaking anywhere upto
20 or 30A.

Your teacher needs to go back to school !!

For servos I'd have chosen LiFePO4 2S battery pack, which at 6.6V would be much less likely to
blow up servos.  Or have looked for higher voltage servos, but that would perhaps get expensive.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

iii2

Get a Battery Eliminator Circuit (BEC). You can Google it.
Hi, I googled it buy I didn't understand very much. Isn't there any simple circuit to make?
I don't have a lot of knowlage in electronics.

You'll need a substantial DC-DC converter for that, you might be peaking anywhere upto
20 or 30A.

Your teacher needs to go back to school !!

For servos I'd have chosen LiFePO4 2S battery pack, which at 6.6V would be much less likely to
blow up servos.  Or have looked for higher voltage servos, but that would perhaps get expensive.
Unfortunately I can't buy this item, its not available in my country and I don't have time for shipping.
If it's possible I would like to use a 8v battery, I have this voltage regaultor
https://www.amazon.co.uk/Pololu-2-5A-Step-Down-Voltage-Regulator-D24V22F6/dp/B018KQVHUW
 to transfer it into 6v.

In addition, is there any simplier solution?
The whole system don't use more than 4A, defintally not 30. All of the servos never work at the same time, and in full range of motion. and usually a servo works for 2 seconds and than he "rest".

I really would like to prefer buying any additional items. In my robotics lab that's a lot of equipment to use, resistors, capacitors, regulators, batteris and many more. If there's is somthing I must have I would buy it, but in the US you have amazon and many others site, and I don't have the option to buy ant items I want. usually I can buy items, but not spesific models or companies.

SurferTim

You can do that. Use a few regulators. Power a few servos with each. Not a problem.

iii2

You can do that. Use a few regulators. Power a few servos with each. Not a problem.
You mean use 2-3 regulators, all set up to 6v?
And connect the regualtors output to the servo card, without pull up resistors or capacitors?

SurferTim

You might need to do a little redesigning of the circuits.

This is what I would use:
HobbyKing 20A BEC

iii2

You might need to do a little redesigning of the circuits.

This is what I would use:
HobbyKing 20A BEC

Won't be able to buy this in my country.
The voltage regulator I posted wouldn't do the job?
Its the only thing I would be abke to buy in the short time I have

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