This voltage protector offers 3,300,000 uF of energy storage in a small and lightweight package.
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more powerful multicopters bring us the opportunity to use bigger cameras, very big and complex gimbals, and of course big and powerful servos.
a servo, being a motor, needs a big available "immediate" energy, which means high current, when it starts moving.
capacitors are used to store energy for fast discharge application, and most of us know the "voltage protector" devices for RC, which are usually about 10,000uF capacitors that are plugging in the RC receiver and will give more stability and stored energy,
with the latest developments of EDLC (electric double layer capacitors) and high energy capacitor,
the ability to use them in the RC field is now possible.
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Comments
Anthony, that's not it at all.
The idea is to use the cap as a storage reservoir to keep up the voltage going to the servos during transients. When servos get a command to move fast, they take a lot of power, which can cause a dip in the voltage supply. The Cap helps supply power during the transient, holding up the voltage.
ultracapacitors or vanadium plating?
I am not sure how this discussion will grow. :-)
Placing 3.3 M uf is huge:-)
I would try 10 uf Tantalum Capacitors near a servo power source to help the pulse drains.
Tantalum capacitors weigh less and can do almost the same. http://www.engineersedge.com/instrumentation/tantalum_capacitors.htm
A large capacitor is generally known as an all round panacea for noise problems. If you are using a huge electrolytic capacitor, for example, just after a ubec, the power on time for the electronics can be considerably slowed. Voltage regulators can fail to reach their designed initial condition, and microprocessors in the autopilot and in digital servos can fail to initialise, seemingly randomly. Some of these super caps have a fairly high internal resistance, so the massive advertised capacitance is just not as effective in reducing noise spikes as the lable might lead you to believe. Now ARHEXA makes some pretty impressive claims, and I do not doubt that in this particular case they are quite genuine. If the reader tries this and does not have the same success, then I suggest he takes careful note of the particular capacitor chosen, and places it in the circuit in exactly the same way ARHEXA has. Otherwise he may be bighting off more than he can chew.
Remember; bigger is not always better.
Two of these in series would give you 10 Million uF of capacitance, at only $10 (plus a bit of heat shrink and an extra servo lead) for $10 USD. You should realize however that these will put a LARGE load on your BEC when it is trying to come up to voltage when you first turn it on. The energy to run your servos and such after you loose power has to come from somewhere, and it will flow from your BEC limited only by the resistance of the wire connecting it and the internal resistance of your caps, essentially shorting your BEC for a period of time (just like when you plug in your lipo you get the pop from the spark). This large load could cause booting problems its self. For the $21 USD the author wants I would install a small receiver pack as a redundancy measure. Also note that your equipment will continue to run after your plane is switched off.
yeahhhh i have a 1 farad, 500gr capacitor in my car stereo .
I will put on my drone hahahahaha
It is one of those "it is not really needed, but since it doesn't hurt let's use one to be sure" things. If you really need one it is more an indicator that you should get a bigger ESC.
I also see some possible problems with using a capacitor.
Firstly, a large cap will take a lot of current to charge when you power up the system. This could be bad for the ESC in the long run, being maxed out for a short time every start-up. So bigger is not necessarily better.
Secondly, if the spike is large enough to drain the cap you could end up getting an even worse after spike when the ESC have to recharge the cap and drive the servos at the same time.
@ John, that is exactly what I'm doing. Just ordered 4 2S rated servos, and I'll round-file the UBEC. It's the simplest solution.
@Gareth, I have the large "voltage protector" from Hobby King, and it can power the APM for 2 seconds, IIRC.
Now, one thing that needs to be said, is that I fear these large cap banks might actually introduce noise into the system. I think I've read that they can pick up EMF and convert it into voltage. I know that I have in the past left my big cap-bank unplugged for a month, then plugged it into my APM, and the power light turns on for a second then dims. It got that voltage from somewhere.
This large capacitor can probably power it for a long, long time.
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