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Servos energy (Robotic Arm)

Update:

Well, now that I have time for this robot I've discovered that the SSC32 supports at maximum 9 volts and my PSU is 12 volts. The website for robotshop says 6v to 12 volts but the documentation says 7.2v. Help me please

Cheers

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Hi, I'm working on a robotic arm, but I don't know what power source purchase. My servos are the problem:

http://www.robotshop.com/hitec-hs-225bb-servo.html X2

http://www.robotshop.com/hitec-hs755mg-servo.html

http://www.robotshop.com/hitec-hs805BB-servo-motor.html X2

Servo Controller: http://www.robotshop.com/dfrobot-32-servo-controller.html


These guys drains like a/an (stereotypical joke here), so I've called to the store, and a technician gave me these options:

http://www.robotshop.com/lipo-battery.html ( Not sure about that)

http://www.robotshop.com/lynxmotion-12-volt-ni-mh-2800mah-battery-pack.html


http://www.robotshop.com/dimension-engineering-parkbec-2.html
( That's new to me)

I have this one but I'm not sure:

My arm sketch is attached.

Please any help is highly appreciated. If I need anything extra let me know.

AttachmentSize
roboticarm.png31.04 KB

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Looking at the manual, it seems like the controller accepts two sources.

One power input (VS1) is to run logical voltage, and accepts from 5.5V to 9.0V and outputs a regulated 5V. So the board already has an on-board power regulator for your logic chips. No need for a separate one.

The second power input (VS2) is for running servos. This will run directly off the unregulated batteries you connect to VS2. You can supply VS2 from a separate battery. If your servos can run as high as 7.2V (some can, most only go to 6V), then you can use a battery up to 7.2V. Otherwise, keep it from 4.8V to 6.0V

You have to set the jumpers appropriately depending on whether you are using one or two supplies.

A 12V supply is no good for this application. The post I linked earlier can give you some ideas on supplying multiple voltages, dropping voltage across a pair of high power diodes to get ~ 6.0V from a 7.2V battery, and other useful ideas.

So, just as an example, you could power everything from a single 7.2V NiMh high capacity racing battery pack. A lower capacity pack of the same style would work too, but won't run for as long. You should calculate the maximum current draw you expect and buy a pack that will run your arm for a decent amount of time.

Anyway, take the 7.2V pack and connect it to VS1. The on-board 5V regulator will supply a clean 5V to your electronics.

Now get some high current diodes. Each diode drops about 0.6V, so by placing two of them in series with the 7.2V battery, you can get 6.0V for the servo power input (VS2). If your diodes are rated at 3A each, and you think you need more than that to supply your servos, you can double them up for greater current handling capabilities. Just take a second pair of diodes and place them in parallel to the first pair. Each pair of two diodes in series drops 1.2V and can handle up to 3A, and you connect both to the + input of VS2.

This is not the only way to do it. I'm just providing an example for you to get some ideas.

I've collected a couple of links on selecting batteries on the LMR Primer page.

These may help you pick the right size/capacity for your batteries, based on the current requirements of your servos and other components.

 

Thanks. Very helpful.

The lynxmotion 12v nimh 2800mAh.

But with that the arm will move properly?

How safe will be the servo controller?

The one I suggested is the highest current option, which will give the longest run time for the arm. As long as there is a regulator built into the controller, it should be fine. Beyond what I have said, I can't really help as I have not studied that area very well.

Thanks for the help : )