12 hobby servo power requiremens

Hi all,

First post on this great community. I have read around and understand the need for an external power supply to run muliple servos, however I cannot work out the rating that supply would need to be in order to safely run 12 turnigy TG9E hobby servos. They are being used to run a model of an animated building facade and will be unlikely to be under very much load.

Any help or suggesions with this would be really appreciated.

Thanks

Paul

Just realised this is in the wrong forum… sorry.

Hi Paul, I run 18 servos that are bigger than the ones you are using. At least 6 and more likely 12 of mine run into significant load. Here is a link to a thread showing how I have them hooked up. http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1265626147/6#6

I got the shield from NKC http://www.nkcelectronics.com/arduino-megashield-pcb.html I soldered in the headers to plug in the servos and ran wires to the digital pins.

Now for power supply - with your 12 smaller servos under little load, you could start by trying any 5v power source and see if the voltage sags in use (do you have a multi-meter to check?). Just tie the ground to the board and everything should work fine.

I used a regulator from Dimension Engineering. Here is a smaller one that might do what you want. It is rated for less servos that you will be using, but with your low load, you might be able to get away with it http://www.dimensionengineering.com/ParkBEC.htm Here is the one I use: http://www.dimensionengineering.com/DE-SWADJ3.htm Or you could use any battery pack in the 4.8 voltage range.

Hi Vinceherman,

Thanks for such a quick response, your examples look great. I think I am some way off having that level of skill. I was hoping to just buy a 5v dc adapter to run the servos off the mains. Is this not a good idea and would I still need the regulator because I am really not sure what that does. I am very new to this electronics malarky.

Thanks again.

Paul

If you go the adaptor route, measure the voltage coming out of it; some aren't regulated at all, and will show more (sometimes MUCH more) than their output states. Ideally, you would also want to measure how much (if any) ripple is on the output; cheap ones can have a lot (you will need an o-scope for this measurement).

What a regulator does is keep the voltage at a certain level, for a given range of input voltage - so if the input voltage goes over or under the regulator voltage (within a certain range), the output voltage will stay the same (also, if the device being powered draws more current and such, it will keep the regulated voltage the same as well).

Servos are designed to operate from 4.8 volts to 6 volts max usually, so a 5V supply is at the low end of that scale (and you don't get the rated torque of the servo, either). I would actually look into an adjustable regulator instead of a fixed one, with proper feedback resistors to set it to six volts.

Also note that if you want to get the spec'ed current rating out of your regulator, you will need to attach a heatsink to it. If you need more current than it can handle, you can usually parallel regulators to give you more current (or, you can group your servos and power each set from its own regulator).

You can probably get by with a 1 amp regulator per 2-4 servos (depending on servo size, load, and distance from power supply).

You might get something like an inexpensive 12v 2a power supply and use a 5v regulating chip for every 3-4 servos for their power supply (your servos are small, so probably don’t use a lot of power). For better servo performance, you can increase the output voltage of a 5v regulating chip to 5.7v using a small diode on the chip ground (see pix below).

Thanks for all this help, I am really appreciative of how helpful everyone is being. I'll have to do a little background reading on the suggestions you are all making, so as I can understand them a little better. As I said I am very new to all this.

Hopefully I can post some pics/video when is all working.

cheers again.

Paul

Hey, zoomkat; thanks for posting that schematic - didn't know you could "abuse" a 7805 that way! I might have to incorporate that trick for the servo power rail in the UGV (Unmanned Ground Vehicle) I am slowly building...

:)

With a servo, you can see a very noticable performance difference between 5v and 5.7v.