Mains Power for Servo... without fire?

Hi All,

Noob here... I have two related questions..

I am working on a project with 10 MG996R servos. The servos specs include:

Operating Voltage: 4.8~6.6v (upper range preferable as they seem to perform better at or above 6v)
No Load Operating Current: 170mA
Stall Current Draw 1400mA

I am trying to work out how to power my servos using external power supplies that can be plugged into a wall and am worried if I get it wrong, I'll cause a fire.. I really don't want to start a fire.

The servos will be spread out around a room (i.e. I'm not building a single robot or object).

  1. How can I power the servos from just one or two power points (i.e. rather than each servo having its own power source), so I can run each servo's cables back to the power point (likely runs of about 10-15ft)?

  2. Alternatively, how do I power each individual servo using mains power? Could I use these USB Voltage Regulators (i.e. Mains > USB adapter (standard 5v) >> USB Voltage Regulator >> Servo)

Thanks for all of your help. It's much appreciated.

Get a 5V 20A power supply (or 6V if you can find one), connect it to the mains and connect the servos to it. But with 15ft long cable runs make sure you use reasonable size wire not the very thin stuff typically used for servo connections.

Steve

Hi Steve,

Thanks for this. When it comes to attaching the servos, do I attach a jack socket like this (link below) to a perfboard, solder a power rail and attach each servo to the power rail? If so, the jack socket I’m linking to has a rating of 30v but only 1A, do I need to find a socket with a rating of 20A?

Really appreciate your help, thank you.

Nick

How many servos might operate at the same time (except at startup when they ALL will)? At startup you should put a delay (200 millis?) between each attach. Those barrel jacks are only 2 conductor, you also need a signal wire.

I normally use perfboard with simple 0.1" header pins like https://uk.farnell.com/amp-te-connectivity/5-826629-0/header-1row-50way/dp/3418388

Available all over the place they snap into 3s very easily and are good for around 3A (plenty for each servo). You can use these with standard connectors that come with the servos or there are plenty of mating connectors available.

Steve

Hi All,

Thanks for the responses. I’ve had a go using Fritzing to mock up what I have in mind… I can’t find any power adapters/supplies in Fritzing so please presume there is a 5v 20A adapter plugged into the breadboard socket and the Arduino is powered by a 5v USB plugged into the mains.

Would this work?

(p.s. I will ensure there is a delay between each of the servos at startup to ensure they don’t all draw at once.)

Thanks again for your help.

Nick

You forgot the common ground with the Arduino.

EDIT: IGNORE THIS COMMENT... I"M HAVING TROUBLE LINKING TO THE CORRECT IMAGE

Ah, I tried to update my original image but it didn't work so here's the circuit WITH the common ground:

Will it work without setting anything on fire?

Right.. HERE is the image with the newly added common ground... will it work??

I can't find any power adapters/supplies in Fritzing so please presume there is a 5v 20A adapter plugged into the breadboard socket and the Arduino is powered by a 5v USB plugged into the mains.

You have used 'breadboard' and 'perfboard' in your descriptions of the power distribution for the servos.
Just to head off the chance that you are trying to use a breadboard for this, don't.
The breadboard is great for low current signals.
It is NOT great for larger current demands like multiple servos.

Hi Vinceherman,

Noted, I foolishly used the breadboard in Fritzing out of habit. I'm intending on using a Perfboard and soldering it all together. Will it work if I do this?

Many thanks,

Nick

Yes, that should do. The length of your wires to the servos may require heavier wire as noted above.

That's great. Thank you.

Nick

I need a little more advice..

I found this 5V 20A power supply. If it is the correct one to use then I need some specific advice on how to connect it all to my circuit...

  1. Is that an ok power unit to use to provide 5V 1400ma to 10 individual servos that are 10-15ft away from the power source?

  2. In order to connect the power supply to the mains, do I use any old kettle lead, cut the kettle-end off and connect the Live, Netural, Earth to the Power Supply inputs?

  3. Also, to run power across a 10-15ft distance, what specific thicker wire could I actually use? Is this 1mmsq considered thick?

Thank you all for your time.

njwheelbarrow:
I need a little more advice..

I found this 5V 20A power supply. If it is the correct one to use then I need some specific advice on how to connect it all to my circuit...

From the negative (and informative) reviews (see below), that's likely a piece of unbranded junk, I'd advise you
not to ever risk an unbranded cheap mains power supply, many of them are dangerous.

These days anyone can sell anything on eBay and Amazon without any comeback it seems.

Reputable branded power supplies are found from reputable electronics suppliers, not eBay/Amazon.

Multiple dry Joints and some not soldered at all. Earth is insulated from the metal chassis with a bit of what looks like masking tape. Chassis was not connected to earth at all so not properly earthed as it should be. Will not be using this in my project as i am concerned about the safety and design.

Hi All,

I'm planning on powering a Adafruit Servo Shield with an enclosed 5v 20A power supply.

I am attaching 10 servos to the shield, each drawing a max of 1.4A (hence the 20A power supply). My question is, does the rating of the 2core cable from the power supply to the shield need to be 20A? It's really expensive and I'm wondering if it is overkill?

The Cable run from the power supply to the servo shield will be approximately 20ft.

Thanks for all of your help.

“ each drawing a max of 1.4A”

Please double check this.

Hi Larryd, specs say "Stall Current of 1400ma", isn't that 1.4A?

Specs here

Yes

What will these motors be driving ?

Each servo will be turning a bell to ring it.

N