Brushed motor controller

[mjsas]

I am building a model boat and would like to build it for very little money. I cut down a Cherry tree for the wood (really!) and found a free motor. Made the prop and all that drive stuff.

I also found a Tx/Rx in a junk car.

Now I need a circuit for the brushed ESC. Does anyone have a circuit to go from the servo signal to PWM?

[rmteo]

http://homepages.paradise.net.nz/bhabbott/bridge.html
http://homepages.paradise.net.nz/bhabbott/esc.html

[coriolan]

When I was running boats with brushed motor I used that design very
succesfully with up to 12 cells (14.4V)in racing mono or hydro:
http://www.stefanv.com/rcstuff/escbec.htm
There is no reverse, but on a speed boat you can't reverse anyway! :cool:

[Ron van Sommeren]

Several diy designs
http://www.rcgroups.com/forums/showthread.php?s=&threadid=157193

Vriendelijke groeten ;) Ron

[mjsas]

Thanks, this will help.

So far I have about $30 U.S. invested, mostly the LiPo battery pack and spar varnish. The ESC is the last part. It feels good when the varnish is the second most costly item.

[Charles Beener]

I have one that I built
Check it out at.

http://wb8lga.atco.tv/page4.htm

I have ran it a 14 volts and 50 amps. My two motors don't last long.
running a 6 volt motor on 14 volts. The boat really fly around the
.6 acre pond in about 17 seconds About 800 ft distance.

Charles

[Ron van Sommeren]

... My two motors don't last long. Running a 6 volt motor on 14 volts. ...That makes sense. Keeping everything else the same (gearing, prop, controller) current wants to go up squared with voltage, power wants to go up cubed with voltage. Voltage increased by factor 2,3, therefore current wants to increase by factor (2.3)² = 5.3!, an extra 430%.

I added your link to the diy brushed controller compilation I mentioned before in this thread. Thanks :)

Vriendelijke groeten ;) Ron

[Charles Beener]

I have one that I built
Check it out at.

http://wb8lga.atco.tv/page4.htm

I have ran it a 14 volts and 50 amps. My two motors don't last long.
running a 6 volt motor on 14 volts. The boat really fly around the
.6 acre pond in about 17 seconds About 800 ft distance.

Charles

Here is the new Links

My home page
http://home.roadrunner.com/~cbeener/page4.htm

[Bob Chiang]

A quick and inexpensive solution would be to rig a servo to physically actuate a power switch. You could make a multi-position switch for different speeds and reverse.

-Bob

[coriolan]

:cool: A quick and inexpensive solution would be to rig a servo to physically actuate a power switch. You could make a multi-position switch for different speeds and reverse.

-Bob
that was being used about 20 years ago by Graupner, they had two speeds forward by switching two equal packs beteween serie and parallel and some
other set up with forward and reverse for boats. Was OK for the tame 540
of the period (drawing a measly 15 amps) but it wasn't very long the switch
burned out. In those days ESC where very pricy

[mjsas]

I found a cheap controller on Ebay, cheaper then I can buy the parts to build it and they did all the hard work. I added a booster circuit to increase the current rating. Total cost was about $12.

[Ron van Sommeren]

Motor power may vary (very) slightly with changes in inputs on other Tx functions.

Gelukkig Nieuw Jaar :) Ron

[pldaniels]

mjsas,

The 'input' on that schematic, would that not actually be expecting a 0->100% PWM'd signal, as apposed to only a servo-pulse train (1~2mS in 20mS frame)?

Regards,
Paul.

[mjsas]

mjsas,

The 'input' on that schematic, would that not actually be expecting a 0->100% PWM'd signal, as apposed to only a servo-pulse train (1~2mS in 20mS frame)?

Regards,
Paul.

The input signal would be the output of the 20 amp controller. That would be a PWM signal. The 20 Amp controller normally drives a brushed motor but in this case drives the booster circuit. The booster circuit with three FETs should be able to drive much more then 20 amps. With a little modification it could drive several hundred amps at higher voltages.

This controller has a Pic 12C508 micro which converts the 1-2 msec servo signal to a PWM signal. It also will not start the motor at turn on untill it does the safety thing.

[pldaniels]

mjsas,

Right, got it - perfectly understood now :) Was just a bit concerned that it was a 'handy circuit' but for the 'wrong job'.

I did on another part of RCG produce a "open-source" brushed ESC, I'd be happy to copy the circuit here (it uses a tiny13 or tiny25 AVR) if anyone wants.

Paul.