Hi all…. ok this is for Kojak's lifter….on several occasions i have jammed Kojak's lifter arm open rendering it out of the match ..boo. …..which was extremely unexciting for all. The brushless is connected to a winch gearbox (for weight reasons) with the arm attached to that.

So i want to make some kind of limit switch….but how would this work with a brushless motor?

I'm thinking is there something that could be rigged with a servo tester to override the signals coming from my transmitter? or could i make switch that reverses the power coming from the esc?

Help please
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

could potentially do something with an arduino. I'm too noob to know how though heh.

Why is it jamming anyway? If its pysically getting wedged open put a door stop or something there so it cant open so far
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

It doesn't do it as much when I close the arm cause it sits on really flat metal and i imagine the pressure is more evenly distributed….but if i kept going it would jam when closing to normal position i reckon. Its cause the winch gearbox has so much power and the brushless not having as much torque to unjam a jam i think. So a stopper would still jam i think…a rubbery super ball might stop a jam though.
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

Did some testing ...and it looks like…. if i wired up a micro switch so that it reverses the polarity of both outer brushless wires that would reverse the brushless automatically when the switch gets pressed by the arm…..this would have to work right?

i would just need both these micro switches to turn on at once to auto reverse

http://www.rc-hovercrafts.com/pc/hpghovercraft/3/42.gif
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

you could, though I do worry about blowing something up reversing motor polarity without stopping first, also you would need it to stay reversed otherwise you would reverse when you hit the switch, drive off the switch flip back to normal then drive into the switch again.

Some kind of micro and your limit switches is probably the way to go ;->
(an angle sensor might be more robust in terms of handling the frame bending or some kind of optical sensor, particularly one involving freekin laser beams)

Don't forget you need to deal with failsafeing if you do it.

I imagine this is a product that already exists though?
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Mechanical engineers build weapons, civil engineers build targets

if you switch 2 wires of a 3phaze motor when running it will keep on running in the same direction, without loss of power or any other ill effect.

In essence, our brushless motors work on the same idea, so switching 2 wires when running won't do anything.

That is why RC non sensored brushless esc's have a reverse delay.

Oh so the reversing polarity mid movement is not going to work or it wont hurt the esc?
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

I never tried it witch a brushless RC setup, so don't hold me to it.
The motor not reversing is almost sure. The survival of the esc is a question.

Hmmm so with this I am not exactly sure what to do. I dont think you can do the limit switches as simply as the brushed. While you can probably stop it electrically gettig it to be only powered in reverse is not going to be as easy.

How does it jam?

Wondering if the more mechanical solution might be a better way to go.
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Steven Martin
Twisted Constructions
http://www.botbitz.com

I think the simplest solution is to use a spring on the jamming side, that helps returning the arm to a function position, even if the brushless doesn't have the torque to do so.

Ok so compress a spring then trigger a limit switch which disconnects two of the brushless phases or disconnects power to the ESC.

Once ESC is off spring pushes the arm off the limit switch then power switches back on ESC.

That should work.

Steve
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Steven Martin
Twisted Constructions
http://www.botbitz.com

maybe you can redo it so the arm is driven by a crank like a windscreen washer motor, then it only has to run one way (can use cheap controllers = bonus) and it cant jam as itll just cycle up and down
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

Hi Guys….. thanks for all the ideas
the problem with using a spring is that the arm/winch combo won't budge by pulling on the arm in either direction….probably cause a winch is not designed to let go of a truck that its pulling.

I have never jammed the arm when closing it back down to normal position ….yet... which has the flat part of the arm resting on the flat front of the bot….so maybe i have to weld a big flat piece at the final fully open flipping position and hope that it will help it not jam there to….the other thing i was thinking of was to put a warning light on a micro switch that goes off with a bit of headroom to remind my to hit reverse on the controller.

i could always see if a775 would work to drive the winch gearbox…that way i can use switches to stop it…but it wont make that cool brushless beep sound when i start it up
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

If you're going to have any automated motor reversing strategy, MAKE SURE you use a break-before-make switch, otherwise you could easily cause a wiring/switch/battery/esc fire when both sides of the battery are momentarily shorted through the switch, and the switch contacts weld in that position.

I would think that a DC motor would be easier to configure as auto-stop, by having a limit switch OPEN a normally closed limit switch across a diode that prevents the motor from continuing to turn in the wrong direction. You can drive the motor the other way with the switch in either position because the current is flowing the correct way through the diode.

[img]http://tinyurl.com/n2ufdov[/img]

Could you put a servo tester between a servo and the output shaft of the lifter? The servo would turn one side of the servo tester. The servo tester would turn on an ESC controlling the lifter. The lifter would stop when the servo and lifter shaft are aligned.
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