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Old Oct 22, 2009, 10:39 PM
No drugs to fly high
oracle_9's Avatar
Toronto, Canada
Joined Jan 2004
764 Posts
Help!
Looking for brushed speed controller circuit with reverse (non programmable)

I am making a rc boat and looking for a circuit for a brushed speed controller that I can make. I do have experience making boards and soldering. I am looking for a circuit diagram that does not require those programmable chips and coding.

I will be using sealed lead acid batteries with 6V brushed canned speed 500-600 motors.

I know these have high current especially when switching to reverse, but I read somewhere they use a set of 14V 20A relays to help with the direction change.

Can anyone recommend a circuit?

Thanks.
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Old Oct 23, 2009, 05:37 AM
We want... Information!
Bruce Abbott's Avatar
Hastings, New Zealand
Joined Jan 2001
5,179 Posts
PT-BOAT Electrics / Speedcontroller
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Old Oct 23, 2009, 05:47 AM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
Wow.. whatalotofeffort..
I'd pick up a cheap, used ESC.
..a
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Old Oct 23, 2009, 06:35 AM
"MAYONNAISE"
Acetronics's Avatar
Le Treport, France
Joined Jun 2004
1,398 Posts
ROFL ...

May be this one ???

http://p.loussouarn.free.fr/electro/...r/variator.pdf

its " cost " is some french effort ...

Alain
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Old Oct 23, 2009, 10:36 AM
No drugs to fly high
oracle_9's Avatar
Toronto, Canada
Joined Jan 2004
764 Posts
Hi all,
Thank you, thank you, and thank you!
I did look around the internet, but mostly got the programmable PIC, pixade, versions. Used ESC for boats are still expensives. Also, I like building scratch. :-)

Both look very good. First one says it is a bit jittery, but that is ok since this is for a rc combat warship. Second one is good too. My french is a bit rusty, but I think I can manage.

Thank you all.
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Old Oct 23, 2009, 12:49 PM
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earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
12,709 Posts
Sounds like you would need a "h bridge motor controller". You can do a Google search for "h bridge motor controller" and get a lot of good ideas too.

But controlling high amounts of current makes it much more difficult. it isn't simple. Switching directions under speed means the current is switching and that puts a huge amount of strain, not only on the controller, but the motors themselves too. For example, it is why you can't shift into reverse at 50mph in your car.

A direct DC kind of motor controller needs to be huge because of the heat dissipation needed. So everyone shifted to PWM (pulse width modulation) methods and power MOSFET transistors to control the power more effectively.
here is a boat motor controller, you would need one for each motor to control.
http://hobbycity.com/hobbycity/store...hless_Boat_ESC
the motor controller has logic to prevent you from just slamming into reverse at full speed, otherwise you would destroy the motors.
But they have some radio control car motor controllers that would work for you.
http://hobbycity.com/hobbycity/store...verse_programm.

Relays can get expensive, especially when controlling 20 ampere or more of current. This one might be what you are looking for, but no proportional control though.
here is a example: http://www.elecfree.com/electronic/d...relay-circuit/
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Old Oct 23, 2009, 02:25 PM
"MAYONNAISE"
Acetronics's Avatar
Le Treport, France
Joined Jun 2004
1,398 Posts
Hi, Oracle

Can you find a NE 544, ZN 409 or M51660L ???

Lots ( tons !!!! ) of classical drawings around those specialized ICs ...

Alain
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Old Oct 23, 2009, 04:51 PM
No drugs to fly high
oracle_9's Avatar
Toronto, Canada
Joined Jan 2004
764 Posts
Hi Earl,
I know hobbycity (regular customer), those are for brushless motors and still on the high end. Same for the car speed controller. Would be nice for HC to have more of a selection for car and boats though in the future.

Actually I did buy from www.bidproduct.com They have a 80A forward & 60A backward with brake program for $12. Works, but like you mentioned, a built in brake to stop the direction and then you can go the other way, but the delay is long.

My combat warship sort of needs that instant reverse, to slow the momentum of the boat fast and reverse. The cheapest way a lot of guys there do it is to use a servo and 2 microswitches to go full throttle forward and full throttle backwards. Unfortunately, that system does not have speed control, unless you pulse the stick.
If all else fails, I will use this method.

My motors are Speed 550 brushed motors, costing $3 or $4 each. And yes, they do go underwater at some times when the ship sinks or takes on water. These are meant to be disposible. It would be bad idea for this to use brushless, even the cheap ones.
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