pwm speed control

Discussion in 'Electrical & Radio' started by Nick Park, Aug 17, 2009.

  1. warspiteIRC

    warspiteIRC RIP

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    There I knew I heard of clubs that ban reverse!

    In the IRC almost eveyone has eliminated servos except for the rudder. So when I mentioned MAG switch, I was really thinking of an electronic board version. And yes, I know all about the original design simce I designed it (with my son-in-law, Rick Schultz).

    Marty
     
  2. wrenow

    wrenow RIP

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    Actually, it is pretty common to not use combat reverse in Big Gun from what I understand, though WWCC apears to allow it.
    However, it is not that it is banned so much as that it is not used in combat situations. After all, full-sized ships, in general, could not slam into an instant reverse either. If you try running without reverse (yes, I know that many ships in other formats are optimized for attacks in reverse as set up), I think you will find that strategy, tactics, and situational awareness issues all become far more important. Anyway, it works for us and we like it. Your mileage may vary,and, "whatever sinks your boat" if fine by me.;)

    Interesting about the Team Deltas. I have not come across the Team Delta version of a MAG switch. And, seeing as you can get some ESCs cheaper than a Team Delta, I probably will not see one in my area anytime soon, as we like the variable throttle. We ware in the process of testing one new ESC that cost under $14, and the Polk 100A version works fine for our club (at $20) , even with its 20 second limited reverse.
     
  3. rarena

    rarena Well-Known Member

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    Marty, you use the RCE220, don't you?
    http://teamdelta.com/products/prod2.htm
    It's two relays, I believe
     
  4. wrenow

    wrenow RIP

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    Interesting, Rob.

    The Team Delta site even has a wiring diagram for wiring it as a mechanical H bridge. However, for $36-$48.50, it seems a bit high-priced when you can get ann ESC, and have full throttle control, for a similar or lower price, some of which are already waterproof and don't have the power supply issues of the Team Deltas. Probably why I haven't seen them around here. Either one has gotchas and a learning curve, but the end result of the ESC is a variable throttle rather than just full throttle and all stop.

    The technique discussed on this thread might be useful if you have a radio with no EPA, but, since you can get a 6 channel radio with EPAs for $33 (the Hobby King) or, with all programming cables and express air shipping for an all-in cost of under $60......

    Cheers,
     
  5. warspiteIRC

    warspiteIRC RIP

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    yes Ice, I use the team delta and so does Combat mom, Steve and matt. Yes, it has two large relays that act like the two micro switches in the regular MAG switch. It is slower to operate than the RCE200, so Steve, Combat mom and Matt do not use it for guns but I do use it for guns too because it does not require the diodes that REC200 does and I tend to shoot slower.

    Marty
     
  6. rarena

    rarena Well-Known Member

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    That's what I thought. It is also useful for turning pumps on and off or working other accessories.
     
  7. wrenow

    wrenow RIP

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    Meandering a bit far from the original topic, but, you might find it interesting that I had a pump with an APC (automatic pump circuit), that died. For a quick workaround at NABGO, I just slapped a spare ESC in and "done." Since the radio has a spare proportional channel, I can even adjust pump speed to try and kill voporlock. I have used inexpensive aircraft ESCs for pumps for years - before I got into using APCs.
    Also, I am considering using the Vex Motor controller as a fire control with a cuple of soolenoids diode "or"ed. Simple wiring - no separate battery connecitions. Servo wire to RX, and output. Only handles 1A continuous, but should be fine for solenoid servos (the Clippard Mouse valves I use, anyway).

    I gues to the man who has a hammer, every problem looks like a nail.:)

    Cheers,
     
  8. Triorieel

    Triorieel New Member

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    I don't think someone mentioned this, but a simple h-bridge will do the job if you want pwm with forward and reverse.
    ie: http://www.rcgroups.com/forums/showthread.php?t=300737 (I'm just using the picture on this site to give you an easy layout to understand how it works, those specific components may not work for you)
    note: becareful of the components you choose if you deviate. You will need fast diodes to handle the feedback from the motors if the transistors do not have them included internally as well as make sure you are giving the proper voltage to turn the transistors on and off.

    Edit: Forgot to mention...give it a few ticks when changing direction as it may change fast enough to create a short. If you read the datasheet on the transistors you use, it will tell you how long it takes to turn on and off. If I remember correctly, the last project where I was using 85Amp transistors was I think 200 to 400 nanoseconds (don't quote me on that).