[PSUBS-MAILIST] Re: Motor controller...

[Subscuba@aol.com]

Hello John,

I hope you can overlook that I copied your message below but it's easy to address the questions.

Ken


> Hi Ken, John Farrington here (building a K-350-like sub).
>
> I've been trying to decide on motors for my sub and have been skimming
> your motor controller schematic a little bit.  (Electronics is not my
> strong point - but I do have a little experience with it).
>
> I've been looking at the Minn Kota motors to use as main propulsion as
> well as thruster motors for our sub.
>
> I see your schematic is designed for a 70AT/H motor.  I cannot find this
> motor on Minn Kota's webpage, but assume it's roughly a 70# thrust motor.
>
> Something in that range would be fine for our thruster motors, but that's
> not enough for our main propulsion.  I see that they've got a 101# thrust
> model that also runs on 36 volts.
>
> So, here are a couple of questions, if you don't mind:
>
> --------------------------
> Do you think that your schematic could be modified to handle the higher
> current draw (37 amps) just by swapping out M1-M4 with 'beefier' ones,
> or by adding 1 or two more of them?


The 20 kHz Pulse Width Modulator (PWM) was designed to handle 50 to 60 amperes. The 37 amperes would be no problem.

> Would TX1 and it's associated circuitry have to be changed?


TX1 is a simple current sense transformer and would not have to be changed. How ever it would easier to make one for you. It's almost trivial.

> Is this a PWM circuit?     (See, limited knowledge of electronics ;-)


This is a 20kHz PWM control having current limit and duty cycle control. It is more efficient then any controllers I could buy on the market.

> Have you built one, and/or do you have a printed-circuit-board layout?


I built a breadboard to check it out before building it for my sub. I built it on perf board. Thus I did not build it on a PC board. It runs my sub quite well without any problems, so far.

> Thank you very much for any input.


Probably the best thing to do is to send me the motor specs of the motor you want to use and let me design you a controller that meets all your needs, such as control from a remote location. It would be far easier for me to design and build to your needs. I would not want any money for this, but you would have to pay for the parts. I can give you my background if you want. I've got plenty of experience.

Whatever you decide, good luck. Motor controllers are easy compared to what I do at work. It would be fun,

Ken Martindale

> -John