Why the large electrolytic capacitor on the Myxa?


(Keenan Johnson) #1

I couldn’t help but notice that the Myxa motor controller has a large electrolytic capacitor instead of the much smaller board mount capacitor on the Orel 20.

I was wondering why the change? In my experience the easiest part to damage is the large capacitor.


(Pavel Kirienko) #2

The pictures we have on the website are of a late prototype. The actual production version is a bit different, see the following pictures:

You can see that the capacitor is much smaller here, and it is glued to the PCB to withstand vibrations.

We’re offering Myxa in three variants, by the way:

  • In a transparent heat shrink tube, pictured below.
  • In a 3D-printed SBS/ABS enclosure.
  • In an aluminum milled enclosure with a heat sink. This type of enclosure allows Myxa to dissipate more heat, so the maximum power output can be increased up to 600 W.


(Roger Smith) #3

Pavel,

Have you considered Currawong’s approach on their ESC,

They claim to use a unique low impedance ceramic capacitor array because it outperforms electrolytic capacitors, which typically suffer from performance issues at altitude and can degrade over time.


(Pavel Kirienko) #4

Yes, we have. The downside of that design is that it increases the price of the device approximately twofold, which makes it impractical for many applications. We have designed a customized version of Myxa for one of our clients though which leverages ceramic caps at the cost of being considerably more expensive.

What you said about the downsides of electrolytic capacitors is true; however, I would like to point out that the capacitor used in Myxa is a high-reliability high-MTBF model United Chemi-Con EKZN800ELL391MK25S rated for -40+105 ºC, 10000 hours at +105 ºC. Myxa is designed for 3 years of service life with the projected MTBF of 70000-100000 hours, and this particular capacitor fits the service time requirement well.