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Electric Motors, Gearing, Speed Controls, Gyros, Receivers, and Other Electronics Discussion Electric Motors, Gearing, Speed Controls, Gyros, Receivers and Other Electronics Discussion |
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08-14-2012, 07:37 PM | #1 (permalink) |
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HV Setup 12S Need To Understand...
Hey Guys....
well i'm flying now for about 2 years ... but i'm dealing with from 3 - 6s setup... i'm about to get a TREX 600 wich needs 12s setup.... please can anyone make me understand it and how it's done and whats the difference between regular servos and HV once...? and when i use and how.....? and everything about high voltage setup.....? if there was a thread saying all this please let me know cause i searched in helifreak and i couldnt find it..... thanx guys.....
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08-15-2012, 12:30 AM | #2 (permalink) |
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The HV vs. nonHV decision is usually made by deciding between:
- The lower price of non-HV servos and - A belief by many that HV setups have one less failure point (they don't need a BEC) HV also offer additional torque and speed, though many pilots will be unlikely to feel the difference on typical helis when doing typical flying. If you go non-HV, connect a BEC to one or two of the batteries (in your case, ~25V or 50V) and power your electronics off its lower output voltage (~ 6V). Wiring diagrams tend to look like this drawing at the bottom of the page. Do not skimp on the BEC - run too close to the mex specs. A brownout can ruin your whole day. If you go HV, it is likely you'll buy a small 2S Lipo or Life receiver pack (in addition to your two main batteries) with servo-style connections to plug in to the receiver and provide power to it and thru it to the other electronics. Remember not to fly with this too low in power... In this scenario, your receiver, all servos, and FBL controller also need to be able to handle the higher voltage from the receiver pack. IMHO, it comes down to a choice of finances, minor performance gain, and choice of failure point (a BEC or an extra battery). I will probably go HV when I buy my 700. Your mileage may vary. You roll the dice, you take your chances.
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Compass Atom 7HV. Align T-Rex 550. |
08-15-2012, 07:29 PM | #3 (permalink) | |
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Quote:
or u just more like connecting 2s lipo directly to the reciver than connecting through BEC ???
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08-16-2012, 04:02 AM | #4 (permalink) |
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Sorry but I am a bit confused (maybe a bit slow) about what you are asking ? You are talking about a 12s HV setup for the heli motor, and then start talking about HV servos.
No servo (that I am aware of) will run on a direct 12s HV voltage (mind you the same applies to a 6s setup), so you will always need a BEC / regulator etc. You can get HV servos that run on a 2s lipo without a BEC, but this issue is not related to a 12s HV setup for the motor. I run 2s A123 batteries for the standard 6V servos on both of my 12s helis, so not regulator or BEC is required. Are you asking for info about 12s power setups, or info about HV rated servos, or both ? Colin
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08-16-2012, 04:22 PM | #5 (permalink) | |
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Quote:
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08-17-2012, 04:25 AM | #6 (permalink) |
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I think it might come down to how much you want to spend on servos ? A 2s lipo might eliminate a component that might fail (ie. BEC), but you will have the added cost of 4 HV servos.
An alternative might be to get standard 6V servos, and use a 2s A123 or LiFe battery, which usually runs at about 6.3-6.6V, compared to a 2s lipo's 7.6-8.4V. Colin
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Vario Long Ranger 700e Seahawk 600 UH-1N 500 Baumann EC-145 800+ (coming soon ) |
08-17-2012, 04:33 AM | #7 (permalink) |
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How can you run HV servos on 2s lipos, if the voltage when battery is full is 8.4?
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08-17-2012, 10:11 AM | #8 (permalink) | |
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Quote:
and i must chose between geting NON Hv servos 5-6 V with a BEC or HV Servos 8V with 2S lipo directly to the reciver ?
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08-17-2012, 04:37 PM | #9 (permalink) |
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No, that is not what I mean. You can either;
1. Run HV servos directly off a 2s lipo or 2s A123/LiFe, or 2. Run 6V servos off (possibly not ALL 6V servos) off a 2s A123/LiFE, or 3. Run LV servos (4.8V or 6V) off a suitable BEC (may need to choose the right HV 12s BEC, or connect the BEC just to a single lipo of 2s, 3s, 4s, 5s or 6s), or 4. Run HV sevos off a suitable BEC (may need to choose the right HV 12s BEC, or connect the BEC just to a single lipo of 2s, 3s, 4s, 5s or 6s), And there may be a few other options as well. I use Option 2 and have never tried the other options on 12s. Many choose to avoid having more electronic devices than they need to (ie. eliminate the BEC) because it is one less thing to fail, which is why many choose to either option 1 or 2. If you want to have a BEC and find one that has decent reliability on HV, go for it. Remember that a 2s lipo drops down from 8.4V to probably around 7.8V fairly quickly (under load), and many many people here run servos a bit above their rated voltage (ie. run a 7.4V HV servo directly on a 2s lipo), so it is not exactly ground-breaking. I run my 6V rated Futaba BLS servos directly on a 2s A123 at about 6.5V, and have not had a problem. I know of people who have run the same servos directly on a 2s lipo without problems, bit IMO that may be stretching the friendship a little. Colin
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Vario Long Ranger 700e Seahawk 600 UH-1N 500 Baumann EC-145 800+ (coming soon ) |
08-17-2012, 10:30 PM | #10 (permalink) | |
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Is there A BEC that gives 8V constant ??? cause as ur saying that voltage is droping quickly when using a lipo directly that means that i'm risking having brounouts.....?
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08-18-2012, 01:51 AM | #11 (permalink) |
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I am not sure how going below 8V would cause a brownout ? Many of us run between 5V and 6.5V on a Rx without a brownout.
A lipo's voltage drops very quickly from a fully charged state of 4.2V / cell down to around 3.9V / cell, and then drops quite slowly down to perhaps 3.6V / cell (both under load voltages), and then usually drops off almost catastrophically below that (usually the last 10-15% of capacity or so). The idea is not to try to take it that low. I am sure that being a member here for a couple of years you would have seen a lipos initally sharp drop, then flat, then sharp drop discharge curve - if not, perhaps some reading in the lipo forum (there was a couple of threads that referred to the "battery university" I think from memory). Hence your 2s lipo is likely to operate in the 7.2V - 7.8V range most of the time. This sits squarely in a HV servos design range. As I have said above, I do not run HV servos, but I would suspect that all that will happen to them if they were running on 6V instead of 7.2V is that they would be slightly weaker and slightly slower (in the same way that a normal servo will behave on 4.8V instead of 6V) - check out the HV servos specs. Bear in mind that most Rxs can operate between about 4V and 10V (3.5-9.6V for a Spektrum AR7010), and it is the Rx that usually causes a brownout, not a low servo voltage. I think I have reached the limit of my ability to try to explain this, as I have neither HV servos, 2s lipos, or externals BECs. I will give someone else a chance if there is still a query after this. Colin
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08-19-2012, 08:48 PM | #12 (permalink) | |
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Quote:
it's just i dont want to take the risk to make the lipo drop too low so i can have a brownout.....maybe i'm scared to forget about it and not charging it.. so i was just thinking that if i can get a BEC that gives me 8 or 7.8 or even 7.2v and bare myself from forgetting to charge the 2s lipo ( i'm clumzy somehow ) cause thats what i'm concerned about ( forget to charge the batt. ) thats why i was saying getting a brownout dueto low voltage and u thought it's impossible ... belive me with me.... everything is possible things just slips from my mind...... so is there something like that???? ( BEC that gives me the voltage that i need ) and sorry for being such a pain it's just i dont want to lose my heli it's my bigest project till now......
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08-20-2012, 12:35 AM | #13 (permalink) |
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IMO its being stubborn staying with low voltage servos and sticking with a BEC. If you were worried about not losing your pride and joy you would go hv with a Rx lipo. You can put a lipo monitor to tell you the power level of your lipo. Also if you eject you packs somehow, the 2s lipo will still power you electronics. It's just a win win situation going with a hv setup. And like said before, your BEC is an item that will go out, especially if you go with a CC pro.
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08-20-2012, 04:14 AM | #14 (permalink) | |
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Quote:
I dont know if i made my q. clear or not so i'm gonna ask it again ..... is there a BEC that can give me the voltage that i need to work with HV servos?? ( 7-8 v )
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08-20-2012, 05:21 AM | #15 (permalink) |
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If your going HV then just use a 2S LiPo! Much simpler solution and generally cheaper. Also one less thing to worry about too.
With That said, a castle BEC pro can output 8V, I however would run 8.4v on HV servos. Sent from my iPhone using Tapatalk |
08-20-2012, 06:52 AM | #16 (permalink) | |
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Quote:
so here's what i found http://helidirect.com/gryphon-75v-20...mt-p-26363.hdx well one last thing ..... just telll me what do u think about this setup connecting this BEC directly to the 12s lipo putting into concedration that i'm worried about foirgetting to charge the 2s batt. so thats why i'm looking for such setup.... so plz tell me what do u think and whether if it was that bad or it's potentially gonna cuase me trubles....? and thanx again guys u've ben a real help....
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08-20-2012, 10:39 AM | #17 (permalink) |
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Most, if not all, BECs or regulators, same thing, have fully adjustable output voltages.
Set it to whatever you want and go fly. You are over thinking this. As mentioned earlier, a regulator has a harder time dropping 50+ volts of a flight pack rather than 8.4 volts from a smaller receiver pack.
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08-23-2012, 11:33 PM | #18 (permalink) |
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HV and BEC vs. Rx Pack
I think you should be happy with either choice of BEC or Rx pack, at least both are used at the field I go to with satisfied customers on both sides.
On the BEC side there are BECs that can put out both the voltage and amperage an Align / Saavox BL HV servo can consume (though I have heard this can get into the 30A range) and a few different ones that will handle lower power HV servos like the Futaba's. Logic for running HV servos and a BEC I don't know as I have come across some pretty nice 6V servos that are a lot cheaper than the HV servos. Have even seen BL 6V servos for less somewhere I am sure of it. One note is I thought I saw on the Futaba servos if you use a BEC with their HV servos, they said they would last longer on 7.4V than 8.4V continuous as Futaba's thinking was a LiPo would not stay at 8.4V for long. A friend of mine at the field runs the Futaba HV servos and a BEC, no issues so far. On the Rx pack side (this is what I do) there are a couple of things I would like to point out. One on my 600 class machine and the same Futaba cyclic servos as my friend, one 1,800mAH LiPo goes for the entire time I am at the field. Just remember to charge it up before plugging it in at the beginning of the day and I really don't have to think about it after that. As a backup I have telemetry on my radio so it will beep at me if the receiver pack gets too low. I have also seen alarms you can get like this: http://www.amainhobbies.com/product_...-Warning-Alarm If you consider you can either get telemetry or an alarm and you use it, even if some how you forget to charge you Rx pack at the beginning of the day, something like this will beep at you and you are bound to hear it sooner or later. As someone who does the BEC route on my smaller ships and an Rx pack on larger, here are the pros and cons I have seen so far: 1. Pro BEC - Easy to maintain. Light weight. Can use cheaper servos with them and reduce total system cost. 2. Pro Rx Pack - No worry about brown outs unlike BECs. No worries about power train / high voltage mishaps taking away your ability to auto back to earth in a controlled fashion. No worries about BECs burning up and putting 50V across your expensive electronics. (While I have never had a heli BEC do this, I have had several voltage converters for other apps do this frying thousands of dollars of electronic equipment between all of the various incidents.) No electrical noise being transmitted to your heli electronics, which can potentially cause them to glitch up. |
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