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Capacitors and Receivers

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Capacitors and Receivers

Old 10-29-2016, 06:03 AM
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douglas racer
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Default Capacitors and Receivers

I've been doing a little research on adding a capacitor to one of the inputs on my 2.4 Spektrum receiver and I wanted to hear what people here thought. I'm not really worried about brown outs as I think all my airplanes have sufficient receiver power and I've never had an indication of a brown out.. The consensus is that the don't help with that anyway. However, I read somewhere that they can help smooth out the voltage, help with RF interference and servo twitching and since my next airplane I'm planning to fly is my first gasser that appealed to me. Any thoughts? I have one. Is it worth plugging it in?
Old 10-29-2016, 06:40 AM
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ByLoudDesign
 
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You have to have a very large capacitor to hold enough reserve power to make a difference. The people that design the equipment put those type of guards in place to provide good reliable service. If it is the receive, that go with a larger battery of a voltage above the receiver requirement and put in a regulator, then the receives a constant supply of rock solid power!
Old 10-30-2016, 07:20 AM
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jester_s1
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I think on airplanes there is no benefit, but on flybarless helicopters they make a lot of sense. It doesn't take much capacity to make a difference. The big amp draw spikes happen when servos are accelerating their motors and only last for a tiny fraction of a second. You'd never even notice it on a volt meter, but if 2 or 3 happen at the same time it is enough to reset a Spektrum receiver. Since flybarless heli swashplates are constantly adjusting, it is a real possibility that they could cause a brownout. But no airplane maneuver that I can think of would be able to do that, especially without a digital stability system in place.
As for preventing interference, the ignition circuit needs to be electrically separated from the radio circuit. You can do that with a BEC made for powering ignitions, an optical kill switch (needed anyway), or by using separate batteries. Keep the ignition and receiver physically away from each other and make sure your spark plug cap is in good shape and on tightly and you won't have a problem.
Old 10-30-2016, 08:19 AM
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I've got a separate battery with a BEC and opto kill powering the ignition. The ignition is far away from the receiver. I'm using a metal throttle rod but it has plastic ball joint connector on each end insulating it. Still I notice the throttle servo twitching. I have an aluminum servo arm on it. I wonder if going back to a nylon servo arm would help. I'm going to hose clamp the spark plug cap next. I guess I am drifting the thread.
Old 10-30-2016, 09:03 AM
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jrf
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Since Spectrum sells it as an accessory, it seems reasonable to assume that it might actually help. And since you already have one, what have you got to lose by plugging it in?
Old 10-30-2016, 02:25 PM
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Yes but Spektrum says it not for airplane use.
Old 10-30-2016, 04:19 PM
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JohnBuckner
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Is there a thing such as 'to much research' ? Well yes I think its not only possible but quite common. The fellows will often research something to death and invent problems that do not even exist.

You don,t need those things and if you use Nicd or Nimh battery packs for the receiver always make sure you use five cells not four.

Enjoy your new project is that glow or gas powered?

John
Old 10-31-2016, 06:57 PM
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douglas racer
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It's gas. I have dual 6.6v 2000mah Li-fe batteries powering the receiver so I'm not worried about power. I just read somewhere where someone said they help with RF interference.

Last edited by douglas racer; 10-31-2016 at 07:08 PM.
Old 10-31-2016, 07:20 PM
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jester_s1
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There's no such thing as too much research. There is a such thing as bad research with bad souces, and definitely such a thing as overthinking which gets you bogged down in the details to the point where you can't see the big picture. Then, of course, there is not knowing enough to ask the right questions to begin with. But in the end, if one reads quality information and does some solid critical thinking, true knowledge will follow.
Old 11-01-2016, 07:20 AM
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Originally Posted by douglas racer
It's gas. I have dual 6.6v 2000mah Li-fe batteries powering the receiver so I'm not worried about power. I just read somewhere where someone said they help with RF interference.
Folks somewhere say a lot of things that are about as accurate as Mars assuming the size of the full moon. This is about the same, they aren't for airplanes, they are for car racing, no benefit for airplane use and they certainly don't prevent interference.

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