throttle set up with speed adjust-resistor--Question

Discussion in 'Washington Cascade Column' started by joe thomer, Apr 2, 2011.

  1. joe thomer

    joe thomer Active Member

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    change from speed controler to throttle setup with lever switches and speed adjust-resistor. installed the speed adjust-resistor between one of the lever switches and the motors. without the speed adjust-resistor installed, engines run wide open and fast. with the speed adjustor-resistor installed the engines run about half speed, if had to guess. but, there is no adjustment on the resistor. when i move the ring on the resistor fwd or back, the engines run the same speed. followed the wire diagram to install. resistor does get warm, but assume this is normal. any ideas why there is no adjustement on the speed adjustor-resistor?
     
  2. Kotori87

    Kotori87 Well-Known Member

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    Why did you replace the ESC? An on-off-reverse throttle with resistor for speed adjust is more complex and less efficient.

    From your description, I have to ask are you certain you followed the wire diagram correctly? Potentiometers like the one you're using for speed control usually have three contacts: one at either end, and one for the wiper. If you're not getting any adjustment when moving the wiper, then I would guess you attached the wires to either end, instead of to one end plus the wiper. Move one of the wires to the wiper, and you should regain adjustment control.

    If that is not the case, then perhaps a photo could help us debug your problem.
     
  3. joe thomer

    joe thomer Active Member

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    yes, you are right. I need to add one of the wires to the wiper. that fixed the problem. but now have another. boat does what if wonts to. reciever, tansmitter problem.
     
  4. NickMyers

    NickMyers Admin RCWC Staff

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    does it do it on the bench or just while running in the water? Hows the battery voltage? Your resistor is not upstream of the rx is it? Since you removed your ESC you no longer have a nice 4.8V fed to your RX.

    Can you post some pictures of your electrical layout as it is?
     
  5. froggyfrenchman

    froggyfrenchman Well-Known Member

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    Are you running a 2.4ghz radio?
    I have heard that they do not have interference issues with the electronics stuff in the boats.
    If you are running one of the other older types of radios, you may need to make sure you have
    capacitors on your motors.
    You may also have a flakey radio switch.
    You can check that by plugging the battery directly into the rx.
    Mikey
     
  6. joe thomer

    joe thomer Active Member

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    have a 2.4ghz radio
    just matched up the transmitter with the receiver.
    used a spare servo and all the channels are working ok now
    have three servos in the boat, two are cheap and one of those does not work and the other has a case of the shakes. the 25 dollar traxx servo is working fine. going to replace the two cheap 10 dollar servos with some ones that cost more, hope this will fix the problem..
     
  7. NickMyers

    NickMyers Admin RCWC Staff

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    Without looking at your electrical setup I'm guessing you aren't doing anything to step the voltage down from the battery to the RX? If not you're passing full battery voltage level to the servos, some of them will likely not be able to handle fully charged battery level voltage.
     
  8. joe thomer

    joe thomer Active Member

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    your right....how do I step it down then...what do I use
     
  9. NickMyers

    NickMyers Admin RCWC Staff

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    You can buy a BEC, you can use your ESC plugged into the battery slot on your RX (you dont plug in the motors to it, youre just using it to provide the power to the RX), you can use a diode, you can use a voltage regulator.

    Side question: How long did your batteries hold up using the switching instead of the ESC?
     
  10. joe thomer

    joe thomer Active Member

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    seemed the battery lasted longer with the speed control. but then the boat was hauling ass without it. so it ran down faster, but was like a speed boat.
    will look for a diagram that shows how to wire in a diode.
     
  11. mike5334

    mike5334 Well-Known Member

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    You'll find that ESCs are more efficient than a resistor type speed control. ESCs switch the voltage on and off quickly while resistor speed controls rely on pure resistance which wastes power by making heat.

    Probably why the RC car guys switched from resistor speed controls to ESCs two and a half decades ago. Heh.
     
  12. Kotori87

    Kotori87 Well-Known Member

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    You mentioned that the ship was too fast under ESC control. Were you somehow unable to dial down the throttle on the ESC? I know not all radios have the controls to dial down the throttle, but you can also get simple plug-in units that go between receiver and ESC that can dial down the throttle.
     
  13. joe thomer

    joe thomer Active Member

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    Had a speed controller in the boat first. the boat has two engines, counter rotating props. the engines were wired in series. has one speed controller, pro boat 40 amp. the boat would run for about 5 minutes then cut off. only the engine would not work. gun and rudder servos till worked fine. got the boat to the shore, turned off the speed control and back on and would run again, but for a couple minutes then shut down again. same, rudder and gun servos still worked. batter was at 6.4 volts, so enough voltage. though the engines mite be pulling to many amps. since one speed controller for two engines. but followed a wire diagram that showed just that.
    .
    so, changed the then engines to twin 380 motors, thinking the engine mite be bad, pulling to many amps. with same speed controller and ran for about 5 minutes then totally shut down. noticed a little hole in the bottom of the speed control, was not there at the start. gun and rudder servos did not work. so pro boat 40 must have fried.
    .
    so thought I would learn/try the switch fwd and back. problem is getting the voltages down from 6.6 to about 6 or 5.8 volts for the receiver. did get it down to 4.9 volts with resistor and diode. but then the receiver would not power up. with straight 6.6 volts, the cheaper servos have a case of the shakes.
    .
    so going to get a gear drive, so one bigger engine will turn both props and have one speed controller. also going to get a in line meter, to show how many continues amps, peak amps and voltage draw. also install a in line fuse.
    .
     
  14. mike5334

    mike5334 Well-Known Member

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    Hmm ... when running two motors on one ESC, a parallel circuit works better than series. By running in a series, the first motor will get battery voltage (such as 6 volts from a SLA) and the second motor will get approximately half of the battery voltage (3 volts). That means one motor is making more RPM and pulling more amps than the other motor, which could cause higher than normal amperage draws.

    In a parallel circuit, both motors see the same voltage (6 volts from a SLA) and run much more evenly.

    As an example, my Richelieu runs two geared 540 sized motors on one Proboat esc. They are wired in parallel which makes sure both motors have the same voltage, 6 volts. Overall amp draw is higher than a single motor, though the Proboat ESC should easily handle both motors unless there is something majorly wrong with a motor (locked up or other mechanical failure) or the drive system has excessive drag in it. Even then, there was a couple times where a BB got into one of the Richelieu's motors and locked it up for the rest of the sortie without causing the Proboat to shut down. Another advantage to running motors in a parallel circuit vs a series circuit.

    The Proboat BEC sends 4.8 volts to the receiver, not battery voltage. As a side note, 99% of the R/C receivers made today can handle 6 volts without any harm.

    From what you are describing, it sounds like the Proboat was shutting down from excessive amperage draw at first. By cycling the ESC off then back on, you were resetting the ESC. The continued high amperage draw may have eventually fried the Proboat.
     
  15. NickMyers

    NickMyers Admin RCWC Staff

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    Erm, Joe, unless you re-wired the motors differently from when I saw them, didn't you have them in parallel, not series?
     
  16. Hovey

    Hovey Admiral (Supporter)

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    I dont think series or parallel is the issue here. I wonder if the props are cavitating or the motors are just working to hard and that is what is causing the high amp load. If so the solution is to add a gear box.
     
  17. NickMyers

    NickMyers Admin RCWC Staff

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    i'm a big believer in gearing down motors
     
  18. mike5334

    mike5334 Well-Known Member

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    Very true about geared vs direct drive. The stock 540 motors like BC sells turn a lot of rpm ... over 10K. Chatting with other captains, it sounds like the average ship likes around 4 - 6k rpm at the props. Although an ESC can be used to reduce the motor speed down, it would be more efficeient to gear down the motor and use the ESC for fine adjustments to make speed.

    Of course, there are other brands of 540 sized motors that make less RPM that are more suitable for direct drive. Personally, I like the extra torque a geared motor gives. :)
     
  19. SteveT44

    SteveT44 Well-Known Member

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    On my Mogador build I didn't want to mess with gearboxes so I found motors built for relatively high torque in the rpm/voltage I was looking for.

    Steve Tyng.
     
  20. joe thomer

    joe thomer Active Member

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    nick,
    yes, they they were wired in parallel when you saw them, not series, what I mentioned before was incorrect. the diagram below shows how to wire in parallel. with both props turing same way. the way the grap spee was, was in parallel but with counter rotating props. below is wired in parallel with props turning same way. PARALLEL DUAL-MOTOR
    hope I got it right this time


    1. [​IMG]
    As far as a gear box, found on battlers connection a gear box for one motor with two shafts/props. but for a 500 series motor. the only gear boxes they have for a 380 series motor are for single shaft one prop. grap spee has to shafts and two props. you know, if I wired up in series, it was half the revolutions, but mite not fry the speed controller. but did not think it would even make the 100 feet in 24 seconds, but maybe it would.
    also, wired in series as shown below. engines turned half as fast as when wired in parallel.


    [​IMG]
    SERIES DUAL-MOTOR..