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Power Capacitor ??

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Old 04-05-2004, 09:27 AM
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Default Power Capacitor ??

hello, rookie needs some answers.

what are power capacitor for? ( i had one came with my ESC)

and how do i wire it up ? ( where do i solder it to ? )

thank to the pros who can answer my questions.

PS: pics will be great help !!
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Old 04-05-2004, 09:44 AM
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ooops... sorry wrong board.
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Old 04-06-2004, 04:22 PM
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Capacitors help control, the voltage coming through the ESC. They actually work in conjunction with the ESC so that you limit the voltage spikes created. UIt gives teh ESC more control and keeps wear and tear down on the motor. Some ESCs have them built in. How you install is different for every ESC and the ESCs need different ones. Check with the manufacturer of your ESC for guidance.
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Old 04-12-2004, 11:43 AM
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Here is an article saying why a power cap is needed.
http://www.rczone.net/modules.php?na...rticle&sid=373

Check this out!!
I just got this power capacitor. 10,000uF!!!
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3181319214

I tracked down the specs for this capacitor:
http://www.luxon.com.tw/Products/twspec.htm
The ESR (Equivalent Series Resistance) is 0.053
That seems pretty low to allow it to work fast.

Fixed the links.

Last edited by BigBear; 04-12-2004 at 05:18 PM.
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Old 04-12-2004, 11:51 AM
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The RC Zone link didn't work.
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Old 04-12-2004, 12:03 PM
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Caps dont limit spikes, it help limitvoltage depression.

The only time the capacitor does anything is basicaly when you accelerate. The capacitor is charged (from the battery), then when there is a large enough demand for power, as in grunt from the motor, and the voltage across the battery drops below the charged voltage of the capacitor, it discharges. Basically adding current to the esc/motor circuit - increasing low end response. For top speed, it does basically nothing.
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Old 04-12-2004, 12:41 PM
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This text is a reprint of an internet posting. Its old but it goes into detail on whatthe deal is. Its from Novak explains why to use one and what they do. What type of speedo are you running maybe we can give
The Cyclone speed control uses extremely high-speed switching circuitry for the drive power MOSFETS, which are used to control the power to the motor. This method of control is called PWM (pulse width modulation). To deliver 50% power to the motor at a PWM frequency of 5000 Hz, power is applied for 200 micro-seconds (s) and then turned off for 200s, repeatedly. In between being turned on and off, the transistors go through a transition period where they are inefficient. To minimize this inefficient period, the transistors must be switched on and off at a fast rate. Therefore, the speed of switching, which determines the overall efficiency of the speed controller, is important to the design of the speed control. The cyclone's switching speeds are the fastest in the industry, with a Rise Time (off to fully on) of less than 1 s and a Fall Time (fully on to off) of less than 0.8s.

There are several side effects with high speed switching. The more dangerous of these effects are the creation of high voltage spikes and radio noise. The value of these voltage spikes is determined by the current draw, the internal impedance of the battery, and the length of the wire connecting the speed control to the battery. During PWM switching, the battery voltage fluctuates up and down several volts (sometimes decreasing down to just a few volts during heavy acceleration). This fluctuation is called "ripple voltage," and can damage or cause improper operation of the radio system.

To provide smooth power to the speed control and the rest of the radio system, a very low impedance high-frequency capacitor is placed across the battery wires. This capacitor also delivers a large surge current during the valley portion of the ripple. Our test results have shown that at 50% power level, the use of a power capacitor adds about a 7-10% increase in motor RPM, reduces radio noise and increases the radio range. When the power capacitor is properly performing, it gets hot and must dissipate this heat or it will fail. As you have observed, the power capacitor is round in shape. Therefore, placing it inside the speed control would waste a large amount of space and prevent the heat from being dissipated.

Our competition uses several low frequency small capacitors, lined in parallel, inside their speed control to perform a similar function. We felt that doing this would reduce the system's reliability, as heat builds up in these capacitors and they tend to overload and fail. Our design philosophy delivers by far the best solution to this problem and provides flexibility in the usage of available space.
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Old 04-12-2004, 12:49 PM
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My big cap, 10,000 uf at 10v.
Attached Thumbnails Power Capacitor ??-img_0339.jpg  
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Old 04-12-2004, 04:15 PM
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your thinking of using that Tony?Its huge and would do you no good especially since you race rctech.Its weight would be a penelty.

I have one that 1/5 thats size thats 23,000 uf @10volts
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Old 04-12-2004, 04:39 PM
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Of course not. I'm just showing people. Its not that heavy amazingly. You can see I have a different one on my car.
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Old 04-12-2004, 05:18 PM
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I FIXED THE LINKS.

Here is an article saying why a power cap is needed.
http://www.rczone.net/modules.php?na...rticle&sid=373

Check this out!!
I just got this power capacitor. 10,000uF!!!
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3181319214

I tracked down the specs for this capacitor:
http://www.luxon.com.tw/Products/twspec.htm
The ESR (Equivalent Series Resistance) is 0.053
That seems pretty low to allow it to work fast.
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Old 03-30-2018, 09:20 AM
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Default Power capacitor question

Hello!

I am writing regarding receiver power capacitor, I did not have any problem with glitching I was just curious what is actually the difference with or without it. I have Futaba 3PV transmitter with 314SB receiver, so I have the telemetry information about voltage of receiver on my transmitter. When I make fast steering moves with Savox servo motor I noticed that the voltage on receiver start droping from 6V to 4,8V in the worst case. So I decided to install the power capacitor on my receiver and I thought that with installation the voltage will be constant 6V, but there is actually no any difference?
How is work power capacitor and it is OK that is power capacitor connected into S.BUS2 port on receiver? Maybe any ideas or thoughts about topic? See attached electrical scheme.

Thank you.
Attached Thumbnails Power Capacitor ??-power-capacitor-30.3.2018.jpg  
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Old 03-30-2018, 10:35 AM
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Anyone ever heard of maxwell super caps ?
Onnthe full size lines they are amazing ! There 3000f caps (bank of 6 in series ) will start at 7L diesel engine with no battry and only drain it about a volt...
On the rc side there are small versions that could be used in a 3cell seriese configuration . there current capabilities are extreme .
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Old 03-30-2018, 05:18 PM
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Originally Posted by tamiya wrc View Post
Hello!

I am writing regarding receiver power capacitor, I did not have any problem with glitching I was just curious what is actually the difference with or without it. I have Futaba 3PV transmitter with 314SB receiver, so I have the telemetry information about voltage of receiver on my transmitter. When I make fast steering moves with Savox servo motor I noticed that the voltage on receiver start droping from 6V to 4,8V in the worst case. So I decided to install the power capacitor on my receiver and I thought that with installation the voltage will be constant 6V, but there is actually no any difference?
How is work power capacitor and it is OK that is power capacitor connected into S.BUS2 port on receiver? Maybe any ideas or thoughts about topic? See attached electrical scheme.

Thank you.
Try it in one of the normal channel ports like Ch3 or Ch4. I'm not sure if the S.Bus2 port is going to share power with the servo channels or not, perhaps they isolate it. The other ports should be sharing for sure.
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Old 04-02-2018, 02:55 AM
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Also bear in mind that the frequency the capacitor is operating at is much higher than the frequency that the telemetry will monitor at - the capacitor just fills momentary dips in the power supply. It won't maintain the voltage any higher than what the regular demands of the servo are causing.

Maybe if you have an oscilloscope you might see something more meaningful.

Also, since you don't have any issue with glitching, there is no need to fit a capacitor, and nothing to measure. The caps were only used on Spektrum receivers, fundamentally because they were not well designed.
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