Matronics Email Lists :: View topic - Capacitors for trim servos?

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Capacitors for trim servos?

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

rgf(at)dcn.davis.ca.us
Guest

Posted: Tue Jul 29, 2008 1:45 pm Post subject: Capacitors for trim servos?

Hey...not trying to start an argument but as an electronic nobody, these two

advices about caps seem to recommend very different cap sizes (uF). How to

resolve?



Ralph Finch



--

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Tue Jul 29, 2008 3:55 pm Post subject: Re: Capacitors for trim servos?

In motors of this size, 0.1uF ceramic caps will do. If caps get below 0.005uF they may not be so effective, above 0.2 they are getting physically big. But the critical thing is to keep the leads short, and use ceramic caps for their stability, lifetime and voltage withstand.



Often schematics differ since they indicate how the prototype was built. In wideband noise filtering (as opposed to ripple filtering or timing applications) more is usually better. Sometimes the exact values are critical, sometimes not so much. In this case, not so much.



Just use 0.1 uFs 50V ceramic disk caps. Even Radio Shack has them.....

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)cox.net
Guest

Posted: Tue Jul 29, 2008 5:21 pm Post subject: Capacitors for trim servos?

At 02:39 PM 7/29/2008 -0700, you wrote:

 	  Quote: 	
		  



Hey...not trying to start an argument but as an electronic nobody, these two

advices about caps seem to recommend very different cap sizes (uF). How to

resolve?



Ralph Finch


	


   We have a first-hand report that the pair of 272-1436 capacitors

   back to back "did the job". Would something else work as well?

   Probably. My selection of "try it" parts was based on availability

   of parts for a quick look-see. Given that the motor is at the end

   of long, small gage wires, inrush at the switches due to "too large"

   capacity is mitigated. But if you'd like to conduct a science experiment

   an test other sizes, we'd be interested in the results.



   This is always a bit of a crap-shoot. Noise issues are a

   unsatisfactory combination of noise intensity, attenuation

   in the conduction pathway, and noise susceptibility. When

   working qualification issues in the lab, we have benefit

   of calibrated equipment with which we can put numbers on

   all three variables.



   Once the combination finds it's way to your airplane, the

   most you can tell us is that the noise exists and you

   find it unacceptable. The first thing to try is reduce

   the signal at the source. The next thing to try is increase

   attenuation in the coupling mode. The last thing you can do

   is reduce the susceptibility in the victim.



   For the moment, our brute-force experiment to reduce it

   to acceptable levels at the source were successful. Is

   it the optimum solution? Got a few $thousand$ to spend,

   we can take it to the lab and find out.



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum