Noob question: Increase voltage? High-torque servo worth it?

Hardware
1

I’d like to use this servo:

but I’m afraid the Particle won’t power it to get the torque I’d like out of it. My current servo is rated at 3kg.cm @ 4.8V, but that’s probably half or a third of what I’d like. The linked servo is rated at 19.3kg.cm @ 7.4V, which would do the trick great if I could get that voltage.

I know almost nothing about electronics–this is kind of an introductory project for me. I know there are other servos out there at <5V that can get ~12-14kg.cm of torque. But is there any way that I can get the full performance of the one I linked? Increase voltage somehow? Again, I don’t quite understand the electrical science part of this at all. Any help would be appreciated.

2

You will need a separate power supply that can provide up to 3A of current for the servo.

3

@kennethlimcp

New to all of this. Do you know of a single cord that could power both the servo and the Photon? Trying to only use one wall outlet plug

4

You can find a USB 5V 2A adapter easily i think. Something like: http://www.samsung.com/uk/consumer/mobile-devices/accessories/connectivity/ETA-U90UBEGSTD

Try looking around for a higher amperage model with a USB port and it should be easily achievable :smiley:

5

@kennethlimcp

Oh gosh I have a lot to learn. How do you envision this being used? Would I just plug this directly into the Photon and keep the servo plugged into the Photon on the VIN pin? Wouldn’t that still be 4.8V?

Or would I splice the USB cable and pigtail part into the Photon and part into the servo?

Info: I currently have a less-torque servo drawing power off the VIN pin.

6

Something like a Y-splitter would work well - http://www.usbfirewire.com/parts/rr-usb2-splitter.html

I would personally prefer the splicing option but using two separate cables allow for USB-related features without affecting power to the servo.

7

@syndac, I would not recommend powering the servo via the Vin pin of the Photon. The Photon’s onboard protection diode can only handle 3A peak (not sustained) and may overheat and get damaged. Instead, I suggest an approach I used for the Message Torch I built, which uses a large number of Neopixels. However, it will require some wiring and soldering.

Get a good quality 5V power supply with a current rating exceeding the max servo current which, in this case, is 3A. This Adafruit one can supply 4A.

Then get an adapter with screw terminals like this one. Using some hookup wire (18-22AWG), you would connect power and ground from the screw terminal to both the Photon’s Vin/GND pins and the Servo’s power/GND pins. There are other ways to do this including a dedicated servo control board (adafruit) but it all comes down to the need to power the servo(s) separately from the Photon and not through the Photon’s Vin pin when using high-current servos.

8

@peekay123

Thanks for the input. Instead of the adapter with screw terminals, could I use something like this:

with this:

And do you know if the wires in the Photon Maker Kit are the appropriate gauge? I can’t seem to find anything in the documentation.

9

@syndac, the 2.1mm connector is fine but I’m not sure how much current solderless protoboards are rated for. Nonetheless, keeping wires short should be ok. As for the wires in the maker kit, they would need to match the size of the wires on the servo. I believe they should be able to handle the current.

10

@peekay123

Good thinking on the breadboard. After some research, it looks like there’s a ton of folks that use 12V @ 5+ amps. Breadboard models probably vary, but I’ll try it out.

Thanks again for all your help!

1 Like
11

@syndac, one thing you might want to add is a 100uF to 470uF electrolytic capacitor between the power lines on the protoboard. This will smooth power while the servo is moving. :wink:

12

@peekay123

Will do. Thankfully the Maker Kit comes with a 100uF capacitor so I can stop ordering things :smile:

For the sake of clarity, by “between the power lines,” do you mean:

DC adapter -> DC jack -> Breadboard -> Capacitor -> Servo ?

Or:

DC adapter -> DC jack -> Breadboard -> Capacitor -> Photon ?

Or both or something different?

13

@syndac, the capacitor is to reduce noise going to the Photon power so should sit near the Vin pin (between that and GND).

14

So something like this?

Dispenser_bb.jpg1221×651 265 KB

15

@syndac, I would put the capacitor across the power on the power strip. That’s close enough. Otherwise, it looks good!

16

@peekay123

Awesome. Thanks again for all the help!!

1 Like