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Author Topic: Suppressor Capacitors.  (Read 2933 times)

thething84

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Suppressor Capacitors.
« on: April 06, 2016, 03:46:37 AM »

Hey guys.

I bought a bunch of caps off ebay a while back in order to suppress my Brushed motors. Problem I find is the leads are barely long enough to join between poles etc. Where do you guys get your caps from. Or do you buy the premade sets for doing the job?

Thanks

James
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microgyros

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Re: Suppressor Capacitors.
« Reply #1 on: April 06, 2016, 04:09:56 AM »

I buy a bag of one thousand 47nF 50 volt disc ceramic caps at a time from Rapid Electronics and give them away. The leads are 2cm long http://www.rapidonline.com/electronic-components/suntan-ts15001h473msbub0r-47nf-20-50v-5mm-y5u-ceramic-disc-capacitor-08-0237
Data sheet http://www.rapidonline.com/pdf/62494.pdf
Just extend with thin wire or rob some old piece of electronic junk when you have no caps at all.
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derekwarner

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Re: Suppressor Capacitors.
« Reply #2 on: April 06, 2016, 08:31:41 AM »

Guys.....I went back through our archives & found the following posts on the subject.......however all responses are a little different >:-o

18 August 2015
25 April 2014
01 June 2009
11 September 2008

I have two low current [50W] 12 volt geared motors that will require suppression %)
Just wondering if anyone [DM] would care to pen a few definitive lines.......

2 x 0.047 uf caps across the terminals?
2 x 0.047 uf caps across the terminals + a 3rd 0.047 uf cap wired in a triangular link to the motor case??

Derek
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malcolmfrary

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Re: Suppressor Capacitors.
« Reply #3 on: April 06, 2016, 09:24:11 AM »

Quote
2 x 0.047 uf caps across the terminals?
2 x 0.047 uf caps across the terminals + a 3rd 0.047 uf cap wired in a triangular link to the motor case??
Probably should read "1 cap across the 2 motor terminals or 1 across the terminals plus another 2 in series with the connection between them to the motor case."


I find that 1 across the terminals does the job.  Using the other two is basically just adding an extra and doubling the value but with the faint possibility of adding an extra fault liability.  Extra wires = more chance of a short.  If one of the extra capacitors disconnects there is a theoretical chance of an unbalanced circuit which can, theoretically, generate interference.  The theoretical chance of this is about the same as the theoretical chance of the extras doing any good in the first place.


If the capacitor leads are too short to reach, just solder a short (but long enough) length of tinned wire to each of the motor terminals (wrap and solder) then solder the capacitor leads to the tails.  Paint with nice thick varnish to keep it insulated.
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inertia

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Re: Suppressor Capacitors.
« Reply #4 on: April 06, 2016, 09:36:52 AM »

I'll go along with Malcolm ref the use of caps between the terminals and the motor case. I've always used either 0.1uF or 0.22uF ceramic capacitors across the terminals (and 0.01uF between terminals and case), but the value isn't that critical.
DM
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thething84

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Re: Suppressor Capacitors.
« Reply #5 on: April 08, 2016, 01:06:29 AM »

I understand reasoning behind doing it which isn't a problem. its just finding a supplier which doesn't have stupidly short leads.
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barriew

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Re: Suppressor Capacitors.
« Reply #6 on: April 08, 2016, 06:58:52 AM »

Here you go, although I have never had a problem with regular disc capacitors.


Barrie


http://www.componentshop.co.uk/motors/dc-motor-accessories/
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nivapilot

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Re: Suppressor Capacitors.
« Reply #7 on: April 08, 2016, 08:08:23 AM »

I can fully understand the suppression problem with 27Mhz and 40Mhz systems........is it necessary on 2.4Ghz???
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Captain fizz

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Re: Suppressor Capacitors.
« Reply #8 on: April 08, 2016, 08:50:34 AM »

Basically no, but it is considered "good manners" when sailing with other boats using 27/40m
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nivapilot

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Re: Suppressor Capacitors.
« Reply #9 on: April 08, 2016, 08:52:04 AM »

Ah! yes I can see that .... thanks, suppressed it shall be then.
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malcolmfrary

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Re: Suppressor Capacitors.
« Reply #10 on: April 08, 2016, 10:05:51 AM »

I can fully understand the suppression problem with 27Mhz and 40Mhz systems........is it necessary on 2.4Ghz???
In sales theory, it isn't.  But apart from the consideration of not interfering with others, there is the possibility that interference broadcast from the motor leads could be picked up by your servo leads or some other wiring and make its way back into the system.
I imagine that many components today are manufactured with PCB mounting in mind, hence the short legs.  Longer versions will be available, but the simple way is to solder wire to the motor tags then solder the capacitor legs to the tails thus formed and then varnish it.  If its a small capacitor and a big motor, this will probably need to be done anyway.   I find that with my box of capacitors and small motors, the easy way is to poke the wires through the motor tag holes and use the extra length as a bigger tag to solder the wiring to.
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thething84

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Re: Suppressor Capacitors.
« Reply #11 on: April 09, 2016, 02:13:34 AM »

Thanks guys. Well I will continue with what I got and just lengthen the legs then. Was just hoping for a less fidly solution. A new set of magic hands to aid soldering may be called for.

James
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microgyros

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Re: Suppressor Capacitors.
« Reply #12 on: April 09, 2016, 10:16:09 AM »

One capacitor connected between the two terminals will do. How about improvising with materials such as slotted card, epoxy & tape? All of these are insulators.
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