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Thread: Common caps for two escs?

  1. #31
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    Quote Originally Posted by fweasel View Post
    Oh, I see what you did there. Clever.
    I haven't done anything, but the questions didn't get answered. I think what is happening is that the unplugged ESC is getting power from the Y Cable and charges the ESC's caps. Then when he hits the throttle, that cap charge spins the unplugged motor for a short period of time. The Y Cable can't supply the current to keep it going, so the BEC is probably going into current limiting, which cuts off the receiver, then the process repeats. I don't think it is mutual magnetic field coupling because the motor I think (it was a question I asked) is turning in the opposite direction. Plus there is a lot of metal mass on the out runner and it does a good job of soaking up most of the magnetic field. Any field that leaked that much would make a pretty inefficient motor.

    This is a good video showing that current can flow through wires that we wouldn't think of as high current carriers and actually should not be. I love out runners!

  2. #32
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    Quote Originally Posted by CraigP View Post
    That’s cool! Just to re-cap:
    1) ESC 1 is plugged into a battery, while ESC 2 is not.
    Question: Do either ESC’s have a BEC?
    2) Both ESC’s are plugged into a Y Cable
    3) The Reciever is powered up, assuming this true since the motors are responding to a speed input.

    Question: Hard to see from vid, but does the unplugged motor rotate in the proper direction, i.e. opposite of the other motor.

    I think I know what’s happening, but need verification and question answered. Bottom line, you may be demonstrating the exact nature of the problem I was describing. Meaning wire connections can have unattended consequences! Thanks for sharing
    Yes to all questions.
    Your explanation seems very plausible. I agree that it's probably not the magnetic field as I proposed in the vid.
    "Look good doin' it"
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  3. #33
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    That same try to describe on my boat with both T180.
    A single battery. External Bec. "Y" cable. I had just removed the red wire from the "Y" on the side of the RX. Both engines turned ...
    Remove the other two red wires from the "Y" side of the "ESCs" and only the motor that had the lipo connected was working.

  4. #34
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    So as interesting as all this is, the main thing to keep in mind is to watch for unintended current flows in the ground, or minus side. All the electronics rely on the fact that the ground is electrically quiet for everything to work as designed. So I stick to the advice that dual setups should use what is essentially a 3-terminal capacitor, as I posted in the PDF on page 1 of this thread. This keeps the ground quiet. If your ESC’s both have opto-isolation and no BEC, then using that kind of cap with and external BEC will work well. The problem really comes in when you have LV ESC’s such as the T-180, that has an internal BEC. I have not seen a wire diagram that will hold down potential noise problems. I build a small PCB, that has a dual opto-isolator on it. Each channel is independent. I run a control cable from the receiver that provides the throttle signal, ground and power to both opto-isolator inputs. Then each ESC is hooked up to an opto-isolator output and that ESC’s BEC provides the power for the output side of its corresponding isolator. This completely eliminates ground and power loops, but you have to build it. I haven’t found a PC board on the Internet I can just buy. If I run across one, I’ll come back here and post the part number and source with a new PDF to wire it.

  5. #35
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    Very interesting!
    I can try to build it the pcb.
    I'm not an electronic technician, but I'm curious.
    https://static.rcgroups.net/forums/a...75-156-esc.JPG
    I found it sailing ... would it be a combination of two of these circuits?

    One question that occurred to me: futaba has the "DUAL ESC", some benefit in using two channels of the RX? instead of using a "Y"?
    https://www.manualslib.com/manual/12...s.html?page=74
    I do not think the entries in the RX are isolated.

  6. #36
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  7. #37
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    Quote Originally Posted by golfito View Post
    Very interesting!
    I can try to build it the pcb.
    I'm not an electronic technician, but I'm curious.
    https://static.rcgroups.net/forums/a...75-156-esc.JPG
    I found it sailing ... would it be a combination of two of these circuits?

    One question that occurred to me: futaba has the "DUAL ESC", some benefit in using two channels of the RX? instead of using a "Y"?
    https://www.manualslib.com/manual/12...s.html?page=74
    I do not think the entries in the RX are isolated.
    The circuit is close. That’s a circuit diagram, used to show a configuration. It’s not an actual working circuit. If fact with using the battery directly, you could burn out the input on the ESC... They “usually” have an upper voltage rating of 7.5V. The second link is showing the capabilities of that transmitter to do Dual ESC Mixing, a powerful function in the world of twins! It allows you to speed modify the two motors based on rudder input. It’s a feature usually found on the better, more expensive radios. This does nothing for the electrical noise problem. Both ESC’s are still sharing a common control ground.

  8. #38
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    Nicely done Golfito!! The first link shows a solution under “Method 3, Power Domain Isolation, Opto Isolator”. The second looks like a viable part, but I like the cable layout better in the first link. It puts the opto isolator closer to the ESC, to help prevent noise pickup over the wire run. I would need to see the schematic of this part. I’m not sure how they are wiring the outputs on the opto isolator.

  9. #39
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    It appears that West Mountsin Radio no longer makes that opto isolator. That leaves option 2. The east bay rc link on post #36 is in my opinion, a must-read for any FE guy! Loaded with good stuff!

  10. #40
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    I have a radio futaba and the necessary receiver ... do not use that function for recommendations in the FB, Elite RC B ...
    I understand there is no noise isolation.
    Also thinking about a kill swicht if it is possible that adapted work.
    http://www.8fly.it/open2b/var/catalo.../files/787.jpg
    http://www.8fly.it/open2b/var/catalo.../files/789.jpg
    I hope you understand what I'm trying to describe.
    https://hobbyking.com/en_us/opto-gas-kill-switch.html


    And I found this:

    http://www.mtroniks.net/prod/RC-Acce...tm#description

    https://www.ebay.com/itm/D213-Opto-i...8AAOSw~XpZQAQq

    http://rc.305.cz/view.php?cisloclanku=2015100004
    https://www.ebay.com/itm/4-Channel-O...0477631?_ul=AR
    Last edited by golfito; 01-13-2018 at 03:16 PM. Reason: links

  11. #41
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    https://drive.google.com/drive/folde...kFKankzVFVQOFU

    These I can get in my city. Could it be used to build the circuit?
    On Saturday I will try to ingest.

  12. #42
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    Quote Originally Posted by CraigP View Post
    The circuit is close. That’s a circuit diagram, used to show a configuration. It’s not an actual working circuit. If fact with using the battery directly, you could burn out the input on the ESC... They “usually” have an upper voltage rating of 7.5V. .
    Ah hah!!!!! I have been curious about this fact for awhile now but have not seen any manufacturer list specs. I would like to run a HV system but feared the ESC wouldn’t take it.

    BTW guys this is a real good read. I have not experienced any of the loop issues but see room for improvement. Mmm, did lose one side of a twin ESC once mind you with no real cause

  13. #43
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    4_channel_opto_isolator_ic_module_3.jpg

    This is more approximate. I think it could be useful.
    I also followed the advice and link the ground wires of both ESCs.
    26913508_1784045318563868_2029584755_n.jpg

  14. #44
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    Let me draw you a schematic tomorrow. These aren’t showing enough detail. The previous post wasn’t quite right either. You did connect your grounds together in the picture, that’s good. But I don’t think that the forum in general understands the difference between wires and flat plat conductors. It’s just too deep a discussion for this forum, I’m only going to be ridiculed, so I’m not going to explain. Just know there is a big difference! I’ll just continue to build my cap banks in a manner that makes the most sense to me. Not trying to be difficult, it’s just a matter of choice. Your on a good path, I really like your quest to know more. But the open forum just doesn’t work for me. If you want, you can PM me an email address and we can take this discussion elsewhere. In fact, please do that first and I’ll send the schematic to your email. Thank Golfito, look forward to direct communication!

  15. #45
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    You are very kind. Thank you.
    I will send you a private message.

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    Quote Originally Posted by srislash View Post
    Ah hah!!!!! I have been curious about this fact for awhile now but have not seen any manufacturer list specs. I would like to run a HV system but feared the ESC wouldn’t take it.

    BTW guys this is a real good read. I have not experienced any of the loop issues but see room for improvement. Mmm, did lose one side of a twin ESC once mind you with no real cause
    Shawn, will include you on the email traffic. If others have a serious interest in this discussion, please PM me an email and I’ll get you on the list. I think this is the best way to keep this topic going in the positive and constructive direction.

  17. #47
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    Quote Originally Posted by CraigP View Post
    Shawn, will include you on the email traffic. If others have a serious interest in this discussion, please PM me an email and I’ll get you on the list. I think this is the best way to keep this topic going in the positive and constructive direction.
    Thanks Craig, you know I'm all about getting things right.

  18. #48
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    Quote Originally Posted by golfito View Post
    4_channel_opto_isolator_ic_module_3.jpg

    This is more approximate. I think it could be useful.
    I also followed the advice and link the ground wires of both ESCs.
    26913508_1784045318563868_2029584755_n.jpg
    Very interesting circuit. Subbed. Might send email but I'm just lurking.
    Nortavlag Bulc

  19. #49
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    Quote Originally Posted by ray schrauwen View Post
    Very interesting circuit. Subbed. Might send email but I'm just lurking.
    Would love to put you on the copy list Ray! Just posted an updated schematic for dual setups that addresses this ground loop or noise issue, whichever you prefer to call it.

  20. #50
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    Quote Originally Posted by CraigP View Post
    Shawn, will include you on the email traffic. If others have a serious interest in this discussion, please PM me an email and I’ll get you on the list. I think this is the best way to keep this topic going in the positive and constructive direction.
    Too bad you got your feelings hurt even after I explained that I was NOT ridiculing you. The hobby is not worth getting all stressed out about.
    I'd like to learn, but not at the expense of tangling over misunderstandings.
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  21. #51
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    Hmmm, you might want to read what you posted over again. It’s easy to say I’m a snowflake that gets feelings hurt easily. Actually, thought you might want to know, received a PM from another forum member asking if I had done something to upset you. Seems I’m not the only one that didn’t get what meaning you were trying to convey. Some of us are serious about stopping unexplained failures and achieving extremely reliable boats. Sorry we got off track, but you posting about this being all my problem tells me you have other things on your mind. I wish you the best sir and I still enjoy and learn from most of your posts.

  22. #52
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    Quote Originally Posted by CraigP View Post
    Shawn, will include you on the email traffic. If others have a serious interest in this discussion, please PM me an email and I’ll get you on the list. I think this is the best way to keep this topic going in the positive and constructive direction.
    Why take this to a private conversation?
    There are probably a lot of us here on the forum including me that are interested in reading this discussion.

    I run a duel motor cat with two ESC's
    Red wires disconnected on both ESC's
    U-BEC for power to the receiver.

    Also both ESC's wired together on the battery side (+ and -) so each ESC sees the 6S2P setup.

    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

  23. #53
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    Can I ask you a question? Do your ESC’s have Internal BEC’s in them?

  24. #54
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    Quote Originally Posted by CraigP View Post
    Can I ask you a question? Do your ESC’s have Internal BEC’s in them?
    YES


    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

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    Well Larry, we are discussing the problems encountered when running that exact configuration. So this schematic that’s being discussed is really different than your configuration. I’d expect you’re happy with your setup, but are you interested in reading about the potential problems? Before we went off site, it was discussed how running your batts and cap banks in direct wired parallel can create a lot of added stress on the caps, which are already stressed pretty good at these amp levels. The two motors don’t run exactly the same, so the caps see some really high current surges as the motors beat frequency to each other. That was the reason for posting the 3-terminal cap schematic earlier in the thread. Do you see any validity in what I’m saying?

  26. #56
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    Yes the schematic in post #7 is what really me interested in this topic.

    For my setup of 6S2P - would the connections for the 2P be before the cap bank or after the cap bank?
    Two black going into the ESC's joined together, and the two red going into the ESC's joined together.

    I race my boats, what I have noticed in the past before I started running the 2P setup is that towards the end of a race, on the last couple of laps the boat
    would start to pull to the left down the straightaways.

    Seeing that the hull is a CAT, in the turns (right hand) the outside prop is pushed down into the water more then the inside prop.
    So as the race goes on the outside battery is getting run down more then the inside battery, causing the left hand pull.

    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

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    Larry I noticed that the outside motor really draws more mah, 10-20% more! And exactly why I started this thread. Sincere thanks to all!

    So I am thinking this as my plan.
    This schematic should satisfy all participants in this thread.
    If not please speak up.
    Attached Images Attached Images
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  28. #58
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    Jesse

    Your schematic is exactly what I have now.
    I like the cap bank that Craig posted in Post #7
    Put now am getting confused, as he says NOT to connect the two red Battery wires together.

    This means NO 2P setup.
    This does NOT work for me when Racing. ( I need the 2P setup)

    I can see it now I come out of the last turn, my boat stars to drift to the left. The guy right behind me passes me for the WIN on the inside.

    Or I drift out an take out an other boat, CD calls me DQed for not holding my lane, now between the two boats there is over $2,000.00 in damage.


    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

  29. #59
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    This is a tough problem. I can surely see that one batt pack may get less volts on it at the end of the run. Also, I was planning on putting in a small PCB mixing board, that will slow the in-bound motor under steering command and make it turn better, but that will cause differential battery drain as well, especially on a novel course. I’ve read some racers like the transmitters with channel mixing, but they are a bit pricey. There’s a solution here, and I’m interested in exploring it because my boat may show the same problem. The 3-terminal cap solves the excessive ripple problem (well even under single ESC systems, the cap takes it on the nose). Larry, if you give me a bit of time on the CAD, I think I can come up with something that gets the noise out of the control system while allowing for dual battery pack connection. I’ll post something here tonight, but I’ve got to run some calculations. I’ve got an electrical simulator that can give me a pretty good idea on how it will work. Probably get simulation results tomorrow. This is a good one, I like it!

  30. #60
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    Quote Originally Posted by Jesse J View Post
    Larry I noticed that the outside motor really draws more mah, 10-20% more! And exactly why I started this thread. Sincere thanks to all!

    So I am thinking this as my plan.
    This schematic should satisfy all participants in this thread.
    If not please speak up.
    Yes Jesse, that’s the power connections, and that’s the direction it’s got to go to fix the asymmetrical battery drain. But the “problem” comes with the interaction of the control hook up with the battery connections. Jesse, does your ESC’s in the dual have internal BEC’s like Larry’s setup?

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