Senior Member
Craig in my rc always tried to use external BECs. The turnigy are very economical and never brought me problems.
Attachment 156355
Attachment 156356
Attachment 156357
Attachment 156358
https://hobbyking.com/es_es/turnigy-...-for-lipo.html
https://hobbyking.com/es_es/quanum-1...tput-ubec.html
The latter and the castle creations waterproof will be next to try.
https://hobbyking.com/es_es/yep-20a-...ge-output.html
http://www.castlecreations.com/en/cc...or-010-0153-00
Fast Electric Addict!
Golfito, good selections! Remember to use the ferrite ring on the power out to Rec. I add a cap at the Rec, to form a low pass L-C filter at the Rec. I use about 47uF cap at the Rec. The problem with these switching regulators is that their noise output can be just a degrading as the ground noise!
Fast Electric Addict!
Here’s how I add the external capacitor to the Rec. I have connector housings and female pins, so I solder the cap to the pins, then place in the housing. I use an unused port on the Rec to mount it. Having it on a connector makes it easy to remove if needed. You can also direct solder the leads of the cap to the power wires, just ahead of the connector at the Rec. note the ferrite ring. You MUST use the ring if you add a large capacitor, or you could put your BEC into current limiting when powering up the model.
Senior Member
it is understood!
The smallest thing I found in my recycling was 100uF 36V SMD Aluminum and other electrolytic 100uf. But I can buy them.
*!** The low ESR capacitors if it was very complex to locate them where I live. Some distributors did not know them. But I could finally get it and arm my banks caps.
Fast Electric Addict!
Craig
Can you still a U-BEC wired to the main boat batteries with the Isolator between the ESC and the receiver??
Larry
Past NAMBA- P Mono -1 Mile Race Record holder
Past NAMBA- P Sport -1 Mile Race Record holder
Bump & Grind Racing Props -We Like Em Smooth & Wet
Fast Electric Addict!
Yes, that’s how I’m wiring all my boats now. Please read the post above yours. Switching regulators are great, but they make a bunch of noise too, although not the same noise as ESC power ground. It’s really good to add that cap! Noise from the switching BEC is 1/5 th that of the ring alone. BTW, the “ring” forms a toroidal inductor, a special, low noise emitting type of inductor. When coupled to the cap at the Rec, it makes a great Low Pass filter, needed to keep things clean!Originally Posted by TRUCKPULL
Senior Member
I'm using this for having a 7.2v output:
https://hobbyking.com/en_uk/quanum-1...tput-ubec.html
And I feed the servo hv and the RX de futaba.
I am adding the opto circuit between the rx / esc separately in each set esc / motor. The rx de futaba can handle two channels "for the dual esc".
I have the ferrite rings in the ESC and in the UBEC. I just have to place the capacitor in the RX.
My batteries will only share the ground wire (-).
Senior Member
Later I will try to get a mixer to test the internal motor rpm reduction as they commented. I'm surprised by that application.
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I think this circuit needs some proof that it will work. After all, we’re putting these things in our beloved boats! So I’m posting some scope shots of my test with them. I powered up the opto output with a small, 2s battery, real world to a BEC. I fed a 5V amplitude squarewave to each input at a frequency and duty cycle that’s close to a servo signal. They vary quite a bit anyway, no big deal... the first shot is a magnified view in time of the rising edge, scope at 4uS/div. As you can see, nearly instant and clean. The yellow trace on top is input and the lower cyan trace is output. The traces are both being displayed at 2V/div. This, to a servo or ESC, is instant ON. They next trace is the falling edge. It is 10X slower, 40uS/div, but still would be considered as nearly instant to a servo or ESC. The thing to note in these transitions is how clean they are, no over/undershooting. The next waveform is with the timebase at 2mS/div, which is showing three complete servo cycles. This is a duty cycle at the minimum servo position, and the fourth waveform is at the maximum servo position. I’m very happy with these results, and I hope by posting this, you won’t worry about them working as they should.
The picture insert messed up the order, or it’s beyond my abilities, lol! Anyway, the falling edge is the first, minservo position is second, max servo position is third, and the rising edge is fourth...
Last edited by CraigP; 01-21-2018 at 02:28 PM. Reason: Pictures out of order, explained
Fast Electric Addict!
Craig
Those results on the scope look very clean and precise with no noticeable lag.
Very good.
I have some 47uF - 35V caps , are these the right ones for the U-BEC output at the receiver?
Larry
Past NAMBA- P Mono -1 Mile Race Record holder
Past NAMBA- P Sport -1 Mile Race Record holder
Bump & Grind Racing Props -We Like Em Smooth & Wet
Fast Electric Addict!
Those will work! You don’t need a super low ESR cap here, voltage rating is good too. You can use down to 16V on the Rec. I like to use what I have around, I’m thinking we think the same way!
Fast Electric Addict!
OK now I have to find some plugs to solder them into, I know I have some somewhere in these 50 or so small boxes.
Larry
Past NAMBA- P Mono -1 Mile Race Record holder
Past NAMBA- P Sport -1 Mile Race Record holder
Bump & Grind Racing Props -We Like Em Smooth & Wet
Fast Electric Addict!
Yeah, my world too! I’ve got a room full of boxes of small electronic parts. I go crazy trying to dig through it.
Senior Member
Fast Electric Addict!
Leave the values the same for both circuits. Those resistors are in there to make the light emitting diode inside the opto work at speed. A single channel can easily drive both both inputs with the values unchanged.
Senior Member
Then for the simple opto I eliminate that resistance in parallel and I only leave connected the series resistance between pin 1 of the opto and the signal cable that goes to the RX.
Fast Electric Addict!
The resistance across pins 1 and 2 are to discharge the capacitance of the light emitting diode. Each diode needs its own discharge resistor. I guess I’m not following what “simple opto” means.
Senior Member
Sorry. Simple Opto I call it a single 4N35. And I tried to use one of these for each channel of the futaba rx.
In that modification
How would the resistor circuit for a single 4N35 be?
Resistance 1-2 is maintained.
So, I withdraw the series resistance between pin 1 and the signal cable ?.
Last edited by golfito; 01-22-2018 at 12:00 PM. Reason: Delete irrelevant data.
Senior Member
I will put a resistance in parallel, both resistances of 249ohms. It will have half of its value in both and a resulting resistance of 249ohms.
Fast Electric Addict!
A dual opto is exactly the same as a single, only there’s two channels inside the device. Each channel must be wired the same. Treat each input diode the same. You can also wire it any way you want, this is just my circuit design.
Senior Member
My bad English is a limitation, excuse me.
I understand what dual opto and simple. I just wanted to have two simple opto circuits separately. And then use those two circuits to connect one in each ESC. In a RX of futaba with the dual function esc. Using the 2ch and the 4ch for the esc. Each with its opto circuit.
With the parallel, it reduced the resistance values by half. But just try it one at a time. And with the flysky rx.
*!** The real test will be with both teams together in the RX futaba. In dual mode esc. I hope not to damage any of the electronics by connecting both circuits and both ESCs.
Fast Electric Addict!
Are you having a problem when you test? It looks like it’s working in the video. I’m confused what the problem is...
Senior Member
It works. Both channels.
Only that it modifies the original circuit and the values of the resistances. To use it in the RX with "dual esc". But I have no confidence that he is correct with what he modifies. I can not prove it.
I'm going to build another opto board as its specifications and I will not use the dual esc function.
Very grateful for your help.
Last edited by golfito; 01-22-2018 at 12:02 PM. Reason: Delete irrelevant data.
Fast Electric Addict!
Not sure why you’re reducing the resistance so much. This could cause a loading issue on the Rec. The Ohm Meter is lying to you. The circuit in operation does not “see” the combined resistance of 498 ohms. The led inside the device will only drop about 1.5 volts, so the parallel 249 Ohm resistor sees 1.5V across it. If your feeding 5V in from the Rec, then the series resistor “sees” 3.5V. So the Rec signal out has to deliver 20mA, well within its range. If you use your added up value of 498 ohms, which is wrong, the circuit would only pull 10mA from the Rec. So it actually pulls twice the current you think it’s using.
Not trying to be a problem, but I designed that circuit, then tested it on an electrical simulation program I use for my work. I then measured it on my DSO and posted pictures of that. The circuit is right! I’m open to debate about it if you can show me specific voltage/current information that is contrary to my stated facts. I think your just making a bunch of work for yourself and if you put that Rec into current limiting, you’ll be making more problems for your boat than the opto solves.
If I’m misunderstanding you because of the language barrier than I apologize. But you are showing half the resistance in the schematic you posted, I know that’s not the right way to go. You might want to try that with a Rec you don’t care about. Some the rec don’t have current limited outputs, so you could fry it. All in the name of science, I’ve blown piles of electronic parts up over the years!
Senior Member
I apologize for wasting your time. You have all the reason.
I used the concepts erroneously and realized that I must re-read the principles of the law of ohm. And read the data sheet. I wanted to have the circuit for a single 4n35 / ESC. Then use two of them for the dual esc. But I did not know how to solve it. It worked pure luck.
I'm going to buy the components again and build the circuit as specified. I saw the oscilloscope graphics. You did an awesome job.
I can erase the previous messages with my confusion if you want.
Thanks for the support.
Hernan
Fast Electric Addict!
I went back this AM and re-read your posts and they are misleading because those circuits won’t work like the scope shots I posted. I’m not asking to remove anything, because that’s not my place. I think you have to decide what’s best for the thread, and the many people that may read it. It seems we want to leave a path that is easy to follow. I would like to see other modelers build their own. So it would be nice to have a clean direction. Perhaps when you are done investigating I can drop in some clean schematics. There is interest in the single opto board, for single motor boats to break the ESC/Rec ground loop. There is also interest in a dual opto board, one with a single input connector driving both ESC opto’s. This mimics a Y Cable, only with isolation. The Opto Board is the “Y”. And lastly, a two input Opto Board where each input connector feeds one of the isolators, to be used for Trans/Rec packages that have Channel Mixing in the Transmitter or to come off an external mixing board, such as you found. That is my goal...
Not there yet
Craig, Mtroniks kindly cancelled my order so I’m not on the hook for 10 of those.
So I have a question, I have a couple of Spektrum RX’s (MR3000, dual outputs) that at some point along the way seemed to have one of the ESC outputs die. I’m trying to remember which setup they were in, lower voltage so ESC’s with BEC is coming to mind. Would the cause likely be that ground loop?
There were a number of issues when I started twins so I like you have a box of burnt stuff, lol ��
Fast Electric Addict!
Oh gee Shawn, thanks, LOL! Just what my wife wants to see! Kidding aside, yes, this ground loop can cause that failure. I can't believe it's taken me so long to see this... I did a poor job when I first laid out the electrical stuff in the first boat. Normally, I would spy that out from a mile away! I would love to see ALL ESC's come with Opto-Couplers, since I'm realizing (and the simulator is verifying) that a good ground can't be established at both, the Rec and the ESC. It has to be the Rec only. God only knows how bad the noise is in a twin, where the loops quadruple in magnitude. It's amazing that this stuff lives at all! It's only when I started the design process over again for my future twin build that I caught on to it...
I know many will say "it's good enough" and not pay attention. But at some point, the noise will give them some weirdness, and perhaps they spend time and effort redoing wires and placing things in others spots, never really solving the root problem.
Senior Member
Yes, excellent Craig.
I am interested in the three types of opto plates that I described.
Later I will start the construction of the circuit that you verified (simulates cable Y) As you do on the test plate (protoboard).
Greetings.
Not there yet
First off I feel for the wife, well I understand anyway.
Yes now we need to really prove this. There have been many unexplained issues over the last few years. Spektrum radios being blamed perhaps when it was something like this. Each ESC could be more sensitive than the next. As you said perhaps a over current shutdown in the rx(Rec).
Many (ok maybe just a few) have had the boat go out round a course and have a shutdown. Just over and over again. The fix?? A new Futaba radio as I recall. So someone should find out if Spektrum does undead have a Rx shutdown built in. I myself have never had an issue with Spektrum other than antenna things. So I always wondered what was up with these others. Perhaps this is it!!!
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