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General RC Boat Discussion Discuss RC Boats, submarines & hovercrafts in electric or nitro. |
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01-09-2021, 09:51 AM | #11 |
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Re: ESC and old Receiver
If you look at a 2S LiFE pack you really don't require a BEC at all. When first converting to LiFE flight packs I too was concerned with the 6.6V rated output feeding older tech with the 4.8-6V rating and ran 20A Castle BEC PROs to feed the system on the first, with a separate NiMH pack for receiver only on the second and another PRO for the flight dynamics.
That proved to be a waste of money, complexity and weight as the loaded voltage immediately drops to close to 6V and in all the time I have been running them direct only had one servo fail, a Hitec analog of unknown origin or history. The one concern with higher amp draws is to avoid feeding them directly through the receiver since the internal circuitry may not handle it all. This is why some add ons bypass and feed the servos and other systems directly from the battery and only power the receiver enough to run alone. To avoid interference and signal loss some use optical isolation on the signal leads and/or signal boosting. All this is to provide a clean and reliable flight system. True, some servos are capable of significant current draw, but to be honest, back at the beginning could not fathom the kind of output these are now capable of. I remember once getting my finger caught between the arm and body of a dedicated retract servo of approx 90 oz/inches back in the late 80's and thought that was incredible. Now 450 oz/inches or more are available, with brushless motors and titanium gearing, as well. Lightning quick sweep speeds are also available, although with my type of flying the only requirement for anything like that would be a heli tail setup. I find most scale flying does not need anything that fast or even strong. If you look at one of my vids you can see how little the control surfaces move for most of the regime: [YOUTUBE] [/YOUTUBE] Don't be surprised by channel matching. I often complained Futaba seems to have limited the number of receiver channels, even as the transmitter channels increased.... My other complaint was that BERG receivers, by far my favorite 72MHz rigs, were limited to only 7 channels.
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01-09-2021, 04:14 PM | #12 |
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Re: ESC and old Receiver
My concern is drawing too much amperage through the receiver. I wont have any problems with the batteries. As I mentioned earlier I will be using a pair of 12V glass mat deep cycle batteries. Weight is not a concern for me, I will actually need the extra weight.
So what I need is to take the load off the receiver.I am guessing BEC's are the best way to do this. I already have voltage regulators to change the voltage if required such as for the lighting. |
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01-09-2021, 05:25 PM | #13 |
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Re: ESC and old Receiver
There are several ways to isolate the Rx from the rest of the system. I have actually used an item called an "Isolator" that can be seen in the pic. That does nothing but bypass the internal power feed of the receiver and shunt them directly to each channels output. There is still a feed to the receiver, just no power output, just signal.
There are other similar setups such as the Powerbox series: https://www.powerbox-systems.com/pro...x-systeme.html I bought one of their older systems for $1 at an auction that has two independent LiPo inputs and along with regulating those down to 6V they do as described, isolating the power feeds to the servos and other flight systems independent of the receiver. These were originally to allow for higher demand setups such as multiple servos on long extension runs, with newer versions including gyro modules, as well. All basically do just what you want, but you can build something similar by separating power and ground leads external to the receiver with one set feeding the receiver and the rest direct to the flight systems. Signal leads still have to come from the receiver and don't forget it's important for all negative leads to be tied together regardless of system. Also important is that 2S LiPo is NOT the same voltage output as a similar cell count LiFE and unless rated for 7.4V will fry. In fact, many newer components are now HV rated to be able to run direct from that higher voltage, taking advantage of the lower current requirement, (and other conductor factors such as wire size and length) for the same total power. This is the same reason full size aircraft run higher voltage since smaller diameter wire weighs less and when you consider miles of wiring that can add up a lot.
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01-10-2021, 09:21 AM | #14 |
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Re: ESC and old Receiver
I did not know that you could separate the servo feeds to the receiver. But makes sense. I spent a few hours last night researching circuits with multiple Volt sources and a common -Volt bus.
I spent several hours this morning drawing up the electronics for my boat based on this new information and came up with this (attached). Wire length and placement is for clarity of the circuit schematic only. This would be much more labour intensive to make the wiring harnesses but an inviting challenge.... Anyone know where the male and female ends for the servos can be found? Would need circuit board mounted ones as well. I don't know what they are called. Cheers, |
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01-10-2021, 09:35 AM | #15 |
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Re: ESC and old Receiver
Rick over at RPMJETS sells adapters, wire, plugs, pins and crimper tool, all very good quality. I used to pick up what I needed at the Hansen Hobbies booth at the Toledo Show every spring, but cancelled in 2019 with the rumor gone for good so needed another source.
https://rpmjets.com/collections/all Not sure if yours capable, but some of the setups I mentioned prior have the ability to source monitor and isolate a pack if below minimums so does not draw down the second. Only other recommendation and one that may not be necessary is to look at a brushless drive system. Much more efficient than brushed so will give longer cycle times for the same power capacity.
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01-10-2021, 04:01 PM | #16 |
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Re: ESC and old Receiver
I looked at brushless motors a couple years ago but they turn way too fast for my needs and I never did come across a geared one at that time.
The 2 brushed ones I got from England seem of good quality. The other one is a 5:1 planetary drive, actually this is the one I have been using during bench testing. I have taken both the gear sets apart and made sure they were thoroughly lubricated and seem quite robust. I have plenty of battery storage so I don't think I need the advantage, besides I'm having fun building this the old fashioned way. I don't know how many hours a underworked brushed motor is good for but expect it will some time.. Cheers, |
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01-10-2021, 07:15 PM | #17 |
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Re: ESC and old Receiver
That may work fine for you needs, although I have seen some geared brushless setups out there.
What type of 5V regulator are you using? Asking as some switching do not like to power up no load, (found that out the hard way).
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01-11-2021, 05:00 PM | #18 |
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Re: ESC and old Receiver
Not switching, rather large when compared to them and much heavier ( large heat sinks) if memory serves correct rated at 20 amp. I cant remember the voltage range but they turn down to 5V no problem from almost 14V. Again old style stuff... like me LoL
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01-12-2021, 08:32 AM | #19 |
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Re: ESC and old Receiver
With all this talk about ESC's and BEC's, the easiest way to trouble shoot any system is to remove the BEC and use a separate receiver power supply. research your radio system to determine the voltage required, 4.8 or 6 volts, and make a pack.
Another thing not mentioned is the polarity of the wires plugging into the receiver. While most radio systems are fairly standard, there are a few that change the position of the positive servo lead. If the component( whether it is an ESC or servo) is plugged in incorrectly, you have problems. Next, have you tested the Viper ESC on an other radio system? i am not speaking badly about Viper, but there have been issues from time to time that have been reported. Test the ESC on another system to prove that it works. Lastly, old ESC should work without issues on the entire range of radios, whether analog or digital, 27, 72, 75Mhz, or 2.4mhz. The frequency is not a determining factor. The control protocol MAY be a factor in whether your system s having issues, but that is outside of my knowledge base, so hopefully someone else will pipe it. As mentioned before, if you would please state exactly, which radio system you are using, the exactly voltages being supplied, ect, it would help a lot. BYW, I easily run 8 servos on a 1 amp BEC. servo, unless they are high torque or specialty servos, do not draw any substantial amount of current. |
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01-12-2021, 06:52 PM | #20 |
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Re: ESC and old Receiver
The only radio system I remember with different pin orientation were the older Airtronics, with the positive and signal leads reversed to the more common and modern J type which are set up negative/positive/signal. Theirs originally had the signal as the center pin.
Older Airtronics servos can be made to work with the J type pin arrangement by simply swapping the signal and positive pins. Have done that quite often. If memory serves their original plugs also had 3 plastic tabs on one side to set up correct orientation when plugging into the Rx. but been quite a while. If so you would need to shave those off or replace the plug and pins with newer gear.
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