Toronto Electric Model Aviation Club Forum

Toronto Electric Model Aviation Club (TEMAC) => General Discussion => Topic started by: Bobmic on June 21, 2013, 07:58:41 AM

Title: Any reason not to use a capacitor on the Rx?
Post by: Bobmic on June 21, 2013, 07:58:41 AM
I was thinking to add a capacitor (or maybe more ) in parallel to my receiver's voltage input to add another layer of protection.
Even though I am using BEC's on most of my planes I was thinking of adding capacitors a while ago and have many reasons why it should be a good thing but can not think of why not... beside the fact that I haven't seen many who are using this method.
Almost all of my BECs are the Turnigy 5Amp not the CC 10Amp, although I have never had a problem with them I might guess that CC might have a tighter QC although I am not so sure.

Thank you
B.
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: piker on June 21, 2013, 09:43:41 AM
I haven't had to add any extra suppression to anything for years, but I did, at one point have to run the servo lead (with BEC) from a CC 60A controller, though a ferrite ring to eliminate some interference.  Solved the problem completely.

As you say, my understanding is that controllers have caps built in to suppress back EMF... at least that's my understanding.

Robert
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: bfeist on June 21, 2013, 09:46:21 AM
Are you expecting short bursts of high loads that the BEC won't be able to handle? Personally, I wouldn't add circuitry to existing circuitry, it adds variables. If you're not confident just spend the money on a 10A dedicated BEC. For my Revolver (arguably the highest BEC loads of any of my planes) the built in BEC in the ICE 100 works perfectly. Running it at 6V too.

Ben
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: Bobmic on June 21, 2013, 10:20:31 AM
Rob - I was referring to receiver input voltage, the capacitor will only dampen any current spikes that might cause a brownout. This will be more for models that have retracts and a higher number of servos or maybe high torque servos.

Title: Re: Any reason not to use a capacitor on the Rx?
Post by: MarcV on June 21, 2013, 10:43:27 AM
Well Spektrum sells a capacitor to prevent receiver brownouts.
http://www.spektrumrc.com/Products/Default.aspx?ProdID=SPM1600 (http://www.spektrumrc.com/Products/Default.aspx?ProdID=SPM1600)

But adds "This Voltage Protector is not intended for Aircraft use."

Anybody know why?

Marc
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: Ededge2002 on June 21, 2013, 11:16:31 AM
The spektrum brown out issue has been a short fall of the design since early on. The capacitor would give a LITTLE added power but any sustained load would diminish the voltage it provided very quickly.   
Spektrum has worked hard to minimize the low voltage troubles within its genuine receivers but I always wonder how much the clones have accomplished in this.
I have used the CC10 set to 6v with spektrum and never had a brown out or suspicious crash. Enough for me to trust it in my mind.
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: pmackenzie on June 21, 2013, 07:36:12 PM
Quote from: MarcV on June 21, 2013, 10:43:27 AM
Well Spektrum sells a capacitor to prevent receiver brownouts.
http://www.spektrumrc.com/Products/Default.aspx?ProdID=SPM1600 (http://www.spektrumrc.com/Products/Default.aspx?ProdID=SPM1600)

But adds "This Voltage Protector is not intended for Aircraft use."

Anybody know why?

Marc

Because the car guys are the only ones gullible enough to fall for this? ;D

As Ed pointed out, the cap is just too small to make much difference. (IMO)

If Spektrum truly thinks there should be a cap on the battery rails, they should build it into the receiver.

Pat MacKenzie
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: Tom on June 22, 2013, 09:41:34 PM
I'm not sure a capacitor alone will help much.  A large capacitor capable of helping with brownouts would draw such a large inrush current it may damage the BEC and a small one won't store enough energy to keep the voltage up. If you're having a problem with one of your planes I can help you set up a circuit with a big capacitor using a circuit to slow charge the cap to prevent overloading the BEC.  We can try a super capacitor!  I've been looking for an excuse to try one.
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: pmackenzie on June 23, 2013, 07:41:10 AM
Saw this yesterday - much better solution since it would actually work :)

http://www.innov8tivedesigns.com/product_info.php?cPath=22_24_146&products_id=1154 (http://www.innov8tivedesigns.com/product_info.php?cPath=22_24_146&products_id=1154)
Title: Re: Any reason not to use a capacitor on the Rx?
Post by: Ededge2002 on June 23, 2013, 10:46:26 AM
"Innovative" solution!  I would have thought it would be LiFe based but still a neat solution.
Thanks for posting Pat