Problems with TowerPro SG90 servos and Pololu Mini Maestro 24

Community General Discussions
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20160130_143742.jpg (1996556Bytes)

Hi all,

I am in the process of connecting up 18 Tower Pro SG90 servos to a Pololu Mini Maestro 24 controller to complete my build of a Plen 2 (Custom redesigned to fit the above servos and allow space to carry the controller).

I am using an adjustable power supply that has voltages of 3, 4.5, 6, 7.5, 9 and 12vdc.  The label says that the output is 300mA 3.6 VA max.  I am suspicious this could be my problem detailed below.

If I add the servos one at a time (I do this whilst the board is connected to USB and PSU) they all initialise to the correct position as detailed in the Pololu controller software.  I have successfully got up to 7 or 8 servos connected and done a restart to reset positions.  If I add any more the legs just cave in and go into a kind of spasm with one leg going straight and the other curling up and the servos buzzing.  At that point I disconnect power and USB and move the servos manually to the correct position then try power again but still get same result. PICTURE ATTACHED.

I suspect that this may be a PSU issue.  Possibly not enough milliamps.  Can anyone advise what power supply rating I would need if indeed this is the problem?

 

Forgot to add that the voltage I have set the PSU to is 6vdc.

A link to the Plen robot is below

https://plen.jp/

 

A link to the servos is below

http://www.micropik.com/PDF/SG90Servo.pdf

 

A link to the controller is below

https://www.pololu.com/product/1356

 

All advice is greatfully accepted.

 

Thanks.

 

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Additional Info

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SG90 Current

I do not have specific numbers but would expect SG90 servos to individually draw 300am easily while working. It would depend on the load. Power is computed a the product of Voltage and Current. For my hexapod (heavy) I allocate 3.0A per leg.

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Thanks

Thanks for that info.  I guess I will need a PSU delivering 4.5-5v at 5.4amps (4500ma).

I guess eBay is my next stop.

 

Cheers!

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Power Supplies

You want to get switching power supplies. I would suggest you consider multiple modules, 3 or 4. Determine which motors are doing the heavy work and allocate the power appropriately. Chinese specs on EBay etc are typically overinflated. If it says 3A @ 6V for $3US it is probably not real (I have some and they die at 1.5A). Please consider posting a circuit diagram with part numbers for LMR members to view. You may get some useful tips.

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Power Supplies

I am not sure I would have enough room on board the roboat as it is about 2 feet tall.  The chest body cavity has a volume of 55x65x15mm,  The back body cavity is 55x65x35 although two thirds of the 35mm depth will be needed to contain the controller and wiring.

I suppose I could redesign the body quite easily if you can suggest a suitable power supply.

Many thanks for your help.