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Home✈️Aircraft🚁HelicopterGasser Model RC HelicoptersOther › Powering electronics???
08-19-2008 09:13 PM  12 years ago
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jascamera

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san francisco, ca

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Powering electronics???
Guys,

One fellow RR member suggest me that the simplest way to have redundancy of power for electronics is to have two 4.8 battery plug into 2 separate plugs in receivers along with a battery power indicator. He mention he have 10 plus years of issue free with powering his electronics. Anyone who is doing this?? and What do you think?? I can only imagine that it's twice as safe as running one battery pack.

I also have an idea, if I plug one battery in the receiver and another bec with a lipo plug to a different plug. Is this good also??

Jason
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08-19-2008 09:47 PM  12 years ago
TooBizzy

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Georgetown, Ohio USA

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I also have an idea, if I plug one battery in the receiver and another bec with a lipo plug to a different plug. Is this good also??
I don't think this would be a good idea. You would have two different voltages going to the reciever rail.

Most people who wire their recievers with multiple feeds/switches, do it off one larger battery. That way you have the same voltage going to the same connection. One of the important things you will gain from doing this is have double the available amps going to the reciever. 23g wire is only good for about 5 amps, then it starts building resistance and dropping amps. 5 digital servos will pull more than that, especially when all the servos in a heli are being used at the same time. Having double reciever feeds gives you 10 amps available to the rail. A good thing!

I run a 2s2p A123 (4600ma) in my Predator with dual feeds going to the reciever. Works great...
P-Gasser Se, Raptor 50 Se Hyper, Raptor 30v2, Trex450se, 3dx450...
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08-19-2008 11:04 PM  12 years ago
pgkevet

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Wales

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I've just fitted the jewel to my Speckie (haven't flown it yet) but plugged the flight pack Ni-Hm and jewel into 2 rx sockets. The same theory could apply that you have 2 different voltages going in but equally you have 2 power sources. The flight pack goes through a switch with power indicator and the jewel goes direct with a receiver indicator.

That way I can switch on to check etc.. but if I forget (we would never do that would we?!!) and fire her up then the jewel will power up for me..

I plan on finding out tomorrow (weather permitting)

I've also located the switch down by the pull start with one indicator facing backwards and the voltmagic facing forwards..it's all about redundancy.

If worried about power into the receiver then Y- it and use one feed into the rx.. but comes out almost the same.. logic suggesting a single power rail in the rx..?
pgk
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08-20-2008 06:02 AM  12 years ago
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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I've just fitted the jewel to my Speckie (haven't flown it yet) but plugged the flight pack Ni-Hm and jewel into 2 rx sockets. The same theory could apply that you have 2 different voltages going in but equally you have 2 power sources. The flight pack goes through a switch with power indicator and the jewel goes direct with a receiver indicator.

That way I can switch on to check etc.. but if I forget (we would never do that would we?!!) and fire her up then the jewel will power up for me..
It gets better than that, too. If you don't forget to turn on your Rx battery , not only you will fly with redundant power, but the Rx pack will be charged from the Jewel as you fly.

I have stopped wall-recharging my Rx Ni-MH pack more than a year ago. I only do a very occasional discharge-charge cycle (at every second or third Tx charge) just to make sure it still actually delivers the promised mAh, to avoid inadvertently flying on generator alone.

...Bruno.
Spectra G on Avgas 100LL, Jewel generator
T-Rex450SE V2
DX7
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08-20-2008 06:31 AM  12 years ago
Excalibur

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Destination: Earth

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Most people who wire their recievers with multiple feeds/switches, do it off one larger battery. That way you have the same voltage going to the same connection.
Not to stir the pot, but I disagree.

The whole idea of a redundant power system is to have TWO separate batteries with TWO separate switches going into TWO separate slots on the receiver. This provides back up if one of the batteries or switches craps out, preventing a system failure and the inevitable crash. Since all of the power pins on the receiver are tied common as a bus, as well as the ground pins, you can plug a battery into any slot on the receiver since there is no "signal lead" coming from the pack. I have used this system flawlessly on large scale aircraft with ten servos and have had excellent results. It provides a good measure of insurance for safety, as-well-as crash prevention.
One of the important things you will gain from doing this is have double the available amps going to the reciever. 23g wire is only good for about 5 amps, then it starts building resistance and dropping amps. 5 digital servos will pull more than that, especially when all the servos in a heli are being used at the same time. Having double reciever feeds gives you 10 amps available to the rail.
HUH?!?!?!?

It's the batteries that provide current to the load, not the wires. The resistance in a given length and size of wire is a fixed value, it doesn't "build resistance". When a load draws excessive current through the wire, the resistance in the wire causes a VOLTAGE DROP proportional to the current, but does not DROP AMPS. The wire heats up as power is wasted from the battery and does not get completely transfered to the load. The 22-AWG and 24-AWG (gage) wire used on modern servos is MORE than enough to handle the load, even in a stall condition, otherwise, the manufacturers would account for this and use heavier wires.

Also, if you are drawing 10-amps continuously from your battery(s), you're in a lot more trouble than just wire size. Servo load (current) is transient, ie, it varies with the mechanical load the servo is working against. To draw 5-10 amps, you would need to stall all five servos simultaneously, which is obviously a fault condition. I severely doubt anyone is drawing this much current in a normal setup, even with all digital servos.

In the Gasser world, I have found that two redundant battery systems (as described above) work well if you are NOT using a generator. If you ARE using a generator, then a single battery/switch setup provides the needed back up (redundancy).

Xcal
Camper Fuel: It's Not Just for Breakfast Anymore
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08-20-2008 07:02 AM  12 years ago
jascamera

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san francisco, ca

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Good to hear someone confirms this setup.

jason
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08-20-2008 12:37 PM  12 years ago
TooBizzy

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Georgetown, Ohio USA

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I stand corrected on two points. I should have said “Some” instead of “Most” and I did mean “Volts” but typed amps. Sorry, it was a long post…. I’ve read a lot about recievers going into failsafe because of voltage drop. That was the point I was making about running a single 23 gage wire feed to the reciever. Two feeds is better than one regardless whether your running one or two batteries. I think we agree on that.

Also:
I was answering his question about using a battery of unknown capacity plugged into the reciever and then plugging a large lipoly into a bec then to the reciever. So you think this is a good idea?

If I was going to wire in two batteries, they would be the same size and capacities always charged to the same level.
P-Gasser Se, Raptor 50 Se Hyper, Raptor 30v2, Trex450se, 3dx450...
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08-20-2008 02:28 PM  12 years ago
pgkevet

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Wales

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If I was going to wire in two batteries, they would be the same size and capacities always charged to the same level.
I don't see why that should be an issue (if not using a generator).. just add a diode for flow control on each battery lead so one pack doesn't try and charge the other. A decent bec/regulator ought to have that included anyway.

I flew my jewel for the first time today (Thanks Raja!) with a direct Ni-Hm flight pack as described earlier. It works great although I'm going to have to track down an issue somewhere - nothing to do with the jewel I hasten to add - because the nihm through the switch system ends up with flickering indicators when I activate servos whereas a second pack plugged directly into the rx doesn't. At first i thought that might be lack of current available and tried Y-ing a second Nihm - still happens. So it's a fault/resistance somewhere in the cable/switch system <sigh - it's never easy>.

Once the jewel's running it all copes - kudos!

Foul weather and morning -only restrictions so only got a couple of tanks flown testing it all out....
pgk
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08-20-2008 02:43 PM  12 years ago
rbort

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Franklin, MA - USA

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LED Lights flickering
If your're using a voltwatch, it will flicker all the LEDs when you move the servos as it senses the voltage drop from the battery and lights all the LEDs. If you have a Jewel on-board once you throttle up there will be no voltage drop any more and the voltwatch will be pegged full green all the time in flight.

Its normal for the voltwatch. If you don't like that then the voltmagic (similar but more expensive unit) is the answer as it has some capacitor buffer in it to not flicker the LEDs. Instead if the power is low and its in mid green for example, when you power up with the Jewel you will see it move up 1 LED at a time every 5 seconds or so to reach full green possible on the voltage range setting you have it. If the motor is not running and you move the sticks around, it won't flicker all the LEDs - just a different design that's all.

Have fun!

-=>Raja.
MA 1005 Hanson 2703D, 4393 flts
Spectra 27 3DMax, 3455 flts
Whiplash V1-2 Hanson 300, 1982 flts
Whiplash V2 Hanson 300, 907 flts
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08-20-2008 03:34 PM  12 years ago
pgkevet

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Wales

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LED Lights flickering

It's the voltmagic at the front and a cheap towerpro job at the back by my switch (located by the pullstart so i don't forget). and the latter that flickers. But the flickering stopped when i plugged a seccnd pack into the rx. From what you say it was just bypassing the back power draw and is normal.. which would be nice because I was doubting my hand-made extension leads

I'll monitor anyway.. with pack recharge amounts.. because that's commonsense.

Cool, not to have to take the hood off to change flight packs!

Where's the best place to get a simple painted Spectra canopy from, anyone?
pgk
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08-20-2008 09:28 PM  12 years ago
AceBird

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Utica, NY USA

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The resistance in a given length and size of wire is a fixed value, it doesn't "build resistance". When a load draws excessive current through the wire, the resistance in the wire causes a VOLTAGE DROP proportional to the current, but does not DROP AMPS.
Yeah, HUH???

Resistance builds up in the wire and the battery pack as they heat up when you use more current. If this didn’t happen a normal light bulb would be a fuse. That is why you want to make sure your battery and wiring are large enough to carry the max current draw.

Anyway Jason the answer to your first question is yes it is perfectly fine. Batteries can act like huge capacitors. Old timers would sometimes use a battery in a DC power supply to kind of regulate it. Remember batteries will take on electrons and give up electrons and have there own internal resistance to boot. As long as you don’t mix different cell counts together the voltage difference will not be that great. Red Scholefield explains this in great detail on his site.
http://www.rcbatteryclinic.com/welcome.htm

Now the second question I would say maybe, because it depends on how the regulator is providing the lower voltage. Most that I know off are using very fast switching which is nothing more than turning on and off the higher voltage really fast in the form of pulses. With the normal resistance of your circuit (servos and such) and probably some smoothing capacitors it appears as a constant lower voltage. The jewel has to do this too. So I am saying maybe and the determining factor is the regulation. Raja has picked a regulator that works and has some history on it. Anyone could build their own generator. It is the regulator that will determine how successful it works. I chose to buy the jewel rather than build my own where I know just about enough to be dangerous.
Instead if the power is low and its in mid green for example, when you power up with the Jewel you will see it move up 1 LED at a time every 5 seconds or so to reach full green possible on the voltage range setting you have it. If the motor is not running and you move the sticks around, it won't flicker all the LEDs - just a different design that's all.
I prefer the flickering and instantaneous reading without a 5 second delay. An instant reading means you can analyze if you have a mechanical bind in your servo link. This would not be possible with a delay.
Ace
What could be more fun?
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