Servo Wiring

[Red Sand Robot]

So, from reading the documentation I understand that with my v1.03 board I will need to wire a 220μf capacitor between the +5 and GND of the servo.

Would that mean the capacitor would be wired in series with the GND wire before it connects to the board, since there would be still be +5 on one side of the capacitor?
i.e. -----GND Wire------><220μf><---------<GND Pin, Duet

[A Former User]

You're probably looking for an electrolytic capacitor, those are polarized. Connect the negative leg (which is marked on the case) to GND and other leg to 5v.

You can put the capacitor on the motor, on the connector or on the board.

[Red Sand Robot]

@bearer Would wiring it like this work? Sorry, I'm very visual when it comes to thinking about wiring and circuits, just wanting to double check.

[A Former User]

Now its in series with ground. Scrap the ground symbol and move that side to 5v. So that is is in parallel with the servo.

And observe the markings on the capacitor when connecting it.

[Red Sand Robot]

@bearer So like this, correct? The capacitor would be wired in parallel between the +5 and GND of the servo.

[A Former User]

That looks better

[Red Sand Robot]

Awesome, thank you!

[dc42]

Whether you need the capacitor at all depends on the size of the servo. What servo is it?

[Red Sand Robot]

@dc42 Something like either of these, can't remember the exact listing off of Amazon I got them from.

https://www.adafruit.com/product/169?gclid=Cj0KCQjwrJ7nBRD5ARIsAATMxstzXQM3ltsIyAbbzZGCbQgzmdHpIgmKx94lhGbRou-AgeJf_Sjn49EaAveCEALw_wcB

https://www.amazon.com/FPVKing-Helicopter-Airplane-Remote-Controller/dp/B07N2B99B6/ref=asc_df_B07N2B99B6/?tag=hyprod-20&linkCode=df0&hvadid=343191214486&hvpos=1o5&hvnetw=g&hvrand=14170196726056022913&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033692&hvtargid=pla-744356057742&psc=1&tag=&ref=&adgrpid=64450094290&hvpone=&hvptwo=&hvadid=343191214486&hvpos=1o5&hvnetw=g&hvrand=14170196726056022913&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033692&hvtargid=pla-744356057742

[Red Sand Robot]

@dc42 It is a micro servo, 9g weight, 1.5-1.7kg/cm (4.8V-6V) stall torque. Commonly referred to as a 9G servo.

[Red Sand Robot]

@dc42 So if I took two 100μF and two 10μF capacitors and soldered them together in parallel, and then connected that in parallel with the +5V and GND wires for the servo that should work correct? From what I understand, to find the equivalent capacitance when connecting connecting capacitors in parallel you sum of all the individual capacitances.

[A Former User]

Tollerances are usually quite loose on capacitors so I wouldn't bother with the 10uF caps. Given the small size of the servo I'd probably just add a single 100uF cap and if the board is stable and doesn't reset when the servo is under load call it done, and add the 2nd cap if its unstable.

edit: but, yes, your theory for equivalent capacitance is theoretically correct

[dc42]

@red-sand-robot said in Servo Wiring:

@dc42 It is a micro servo, 9g weight, 1.5-1.7kg/cm (4.8V-6V) stall torque. Commonly referred to as a 9G servo.

I haven't conducted any tests with a micro servo. It's quite likely that it doesn't need any extra capacitance at all; but if it does, 100uF should be more than adequate.

The recommendation of 220uF was based on tests I did using a MG996R servo, weight about 58g. I have some 12.5g servos now (HS-70MG) so I'll test a pre-1.04 board with one of those too.

[PhoenixSimon]

@bearer
Hi
I have seen you have mentioned you can put the capacitor on the motor, on the connector and on the board.
What is the proper and safest way to do this?
I have connected the capacitor to the connector just to try the servo but it doesn't look very professional and safe.
How could I connect the capacitor to the board?
What else would you suggest?

thanks

[A Former User]

@PhoenixSimon In decreasing order of likelyness:

• simply crimp both the servo wire and the capacitor leads into the terminal and maybe add some sleeving on the exposed part of the leads
• solder capacitor to the bottom of the board, onto the solder joints of the servo header.
• remove the plastic "shroud" for the servo header then wire wrap + solder the capacitor leads onto the bottom of the header pins
• solder capacitor to pcb inside servo, 3d print new cover.

[PhoenixSimon]

@bearer
thank you very much. I highly appreciate your help.