Recommendation of batteries for 20 Servo motor...

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Recommendation of batteries for 20 Servo motor...

Postby lecture86 » Tue May 19, 2009 2:41 am

My project is using 6 TowerPro SG90 RC servo, 12 TowerPro SG 5010 RC servo,2 Cytron C60S Servo motors, 2 PIC 16F877A, 1 PIC16F84.Any suggestion which type and how many batteries/power supply shud i use? I totally dunno how to calculate whether how to select power supply/batteries. I afraid normal battery will dry up easily.

Hope someone can teach me!Thx
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Re: Recommendation of batteries for 20 Servo motor...

Postby ober » Tue May 19, 2009 8:43 am

lecture86, I would recommend you to use Li-Po, maybe 7.4 2200mAh or high capacity is good enough. Though we only have 7.4V 1500mAh, you can parallel it to get higher ampere of supply and longer usage.
However, I would like to remind you that voltage is the killer of servos. Some servo can stand up to 16V, but standard RC servo can only survive 6.0V max. So be careful.
Cytron only have C36S, C40S and C55S: we do not have C60S :roll:
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Re: Recommendation of batteries for 20 Servo motor...

Postby lecture86 » Tue May 19, 2009 9:00 pm

Sorry, I made a mistake. i am using C55S, not C60S.
By the way, will it be any harm to connect two batteries in parallel?
ANyway, Thanks for helping. ;)
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Re: Recommendation of batteries for 20 Servo motor...

Postby AMD » Wed May 20, 2009 4:29 am

lecture86 WROTE:My project is using 6 TowerPro SG90 RC servo, 12 TowerPro SG 5010 RC servo,2 Cytron C60S Servo motors, 2 PIC 16F877A, 1 PIC16F84.Any suggestion which type and how many batteries/power supply shud i use? I totally dunno how to calculate whether how to select power supply/batteries. I afraid normal battery will dry up easily.

Hope someone can teach me!Thx


are ur project is a mobility type project or rigid type project... :?:

sorry... my english vocabulary are bad...
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Re: Recommendation of batteries for 20 Servo motor...

Postby lecture86 » Wed May 20, 2009 12:56 pm

are ur project is a mobility type project or rigid type project... :?:

sorry... my english vocabulary are bad...


It is a mobility type project.I can show my tilte& requirements below:

A robot will move on 4 wheels on a smooth surface and automatically change into crawling mode (like insects) when it is trying to move on rocky area. This robot has to be activated by a voice command and will move towards its target (a sound recorder). It has to be programmed that it will only move towards the 1st sound source and not any others. On reaching target, this robot must announce the time taken from activation.

I am using:
2 x 360degree servo motors, 2 wheels, 2 castors for car function.
18 x 180degree RC servo motors for insect movement.


Problems:
I don't know how to trace the sound source.
Do batteries enough for the robot
Regarding time taken announcement, i am trying to use RF module to send data to VB on PC to announce time taken.
Regarding surface identification, i am trying to use Ultra Sonic module to sense the surface,any better suggestion?
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Re: Recommendation of batteries for 20 Servo motor...

Postby sich » Thu May 21, 2009 11:31 am

For the battery part, parallel two or more battery is okay but u have to make sure the voltage of the batteries are the same. Before i read ur current posts, i want to recommend u to use SLA (Sealed Lead-Acid) battery for it can supply for longer period. But since you are building a insect bio-inspired robot, it's not a good choice because of the size and weight. So Li-Po is still better for this case.

For providing power to RC servo with rating less than 6V, you can refer to PR18's circuit. It uses a power mosfet along with standard linear regulator to get higher amp for the RC servos.

The torque for the RC servo motors used is very critical since the robot needs to move on 'rocky area'. I don't know how 'rocky' it'll be but low cost servo might not be able to make it if the robot is heavy and the 'rocky area' is steep. Anyway, u can try with ur current settings first. It might work.
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Re: Recommendation of batteries for 20 Servo motor...

Postby aurora » Sun Jun 07, 2009 5:30 pm

Hobby servo can draw as much as 1A when stall. You definitely need high mAh rating battery, i.e. Lipo 3000mAh and above, which should last you 15-20mins. Common AA battery is out of the question. The current draw is too high for this type of battery, and cannot maintain decent voltage. Don't be surprise if your robot is jumpy, and reset frequently. Lipo may rated at 7.4v, but at 100% charge capacity (direct from charger), it is rated at 8.4v. Once it begin to discharge (the first 10% discharge), the voltage will drop to 7.4v and stabilize.

Hobby servos are rated from 4.5-6.0v, so you need to have good voltage regulator circuit to take care the 8.4v. Typical linear voltage regulator are rated up to 1A only, do not use that to regulate 20 servos, you will blow your regulator in no time. Either you use a higher rating VR (costly), passing transistors method, or simply get 1 regulator for each servo. ;)

Heat dissipation is another area which you want to look into. If power is not handle properly, your controller may reset frequently.

If you want to skip that, try 5x NiMH rechargable battery, 2500mAh. Fully charge 5x NiMH still deliver slightly more than 7.0v. A single silicon diode on each servo will do the trick. ;)
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Re: Recommendation of batteries for 20 Servo motor...

Postby ober » Sat Dec 26, 2009 9:33 pm

aurora, good solution you have there! :)
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