Minn Kota motors ESC

[isaacs]

Hi all, I am kind of new to boats and am actually helping a friend on an ROV project. It is kind of a big one and will be using 2 #35 minn kota motors. What ESC should I use? I found some 50A ones on ebay but seems like everyone here is using Novak roosters. Would the 50A ones work? The full load draw on the #35 motor is like 37A.
Thanks,
Isaac.S

[pompebled]

Hi Isaac,

I'm not sure the ebay 50A esc will cut it.

You'll need to know the stall current of the motor and choose your ESC accordingly.

In principle the 50A ESC should be able to handle 37A, but if we are talking about the blue anodized aluminum encased one, I seriously doubt if it will be able to manage that 37 A continuously without extra watercooling.

Regards, Jan.

[boater_dave]

If you are looking for ultimate control of big motors try Vantec (http://www.vantec.com/rdfr.htm) motor controllers. They integrate 2 channel R/C into dual motor control.

Dave

[isaacs]

I'll actually using a arduino for motor control. I could solder up some fets for control but it requires 2 digital pwm outputs and I need to conserve those for other control components and it would be nice to have it modular so I can replace easily if needed. There are cheap car controllers on ebay but only 8.4V and I need 12V at least. I guess Novak is the best way to go.
Isaac.S

[boater_dave]

Have you looked at robot stuff? Sometimes thay have amazing stuff. Or how about MTronics (http://www.mtroniks.net/products.asp/SubCatID/2/brushed-marine-speed-controllers.htm) ? They can handle 12 volt but looks limited to 40 amps. Waterproof, though.

Dave

[keith S]

If you are looking for ultimate control of big motors try Vantec (http://www.vantec.com/rdfr.htm) motor controllers. They integrate 2 channel R/C into dual motor control.

Dave
Vantecs can take on a large load as they have some industrial size ones. Can try MCD as well.

[isaacs]

I am thinking of trying this (http://cgi.ebay.com/REVERSE-14-4V-ESC-12T-FUTABA-TAMIYA-PLUG_W0QQitemZ200279830038) Price is good so if I burn it up I am not out much.

[boater_dave]

I have doubts that that ESC will last in your application. It is a re-badged Chinese ESC available in many forms (Leopard in Canada, Nova in the US, I think). The spec sheet says 200amps continuous! The wire size looks very small and Tamiya connectors are horrible. Would you pass 200 amps through a Tamiya connector?
"Real" high power ESC's have external solder posts so you can make better high amp connections. This looks like it is marketed to slightly above average RC car users. Not bad for the average boat, but you have much higher requirements in your project. Also remember that car ESC's are only meant to run for a few minutes before cooling off.
Sorry to be a drag.

Dave

[nick_75au]

IMHO no "hobby grade" controller is going to cut it, The big problem with the Minn Kota and other large multipole motors is the back EMF they produce. Look at the robot sites, I have used IFI robotics speed controls and can recommend them.

Nick

[isaacs]

Hey thanks guys for the input. Yeah I guess I didn't think about the car guys not going for very long. This ROV will be going down to 900ft so we don't want a burnout while we are that deep. Can't a capacitor take care of the back emf?
Isaac.S

[tghsmith]

I would take a look at the robot zone site and or talk to a battle-bot builder or two, they build their stuff like its life depended on it.. it does.. as they said in the sit-com "big bang threory" after seeing the oposing labs impresive battle bot"all we need to add to ours is a bladder so it can wet itself before its runs away...

[isaacs]

I am thinking maybe using the arduino with a bunch of FETS wouldn't be such a bad option after all. That way I can build it to handle the current.

[Shaun Hendricks]

Back EMF can be handled in many ways but it depends on the return signal levels and voltages. If it's mostly signal stuff, simple things like chokes can kill it and still leave the voltage alone. I believe capacitors are better at dealing with voltage spikes.

I've used 'hobby grade' controllers to drive some pretty serious motors including a large AC brushless one. Worked great, never got hot.

Robotics controllers are nice and very durable, but you pay for it. The easiest way to drive large motors like this is a simple mechanical linear speed controller. Can be had pretty cheap and driven by a servo.

[Myron]

Hey Isaacs,

What type of ROV?.. I'm working on one that currently has a camera and will hopefully have soon have a Side Scan Sonar. We will use it for Search and Recovery of missing persons.

Myron

[isaacs]

This is more of a recovery ROV. Will be used as a work horse type for attaching cables, maybe doing some dredging etc. We'll see how it operates and go from there. Version 2 we want to be expandable so it can have attachments. What does your design look like and how big is it? There is a design I really like by a swedish company called the SeaGoo. http://www.youtube.com/watch?v=TMio2MZGs0M They are using a ps3 type controller in a cool case. I am not sure if I'll go ps3 or rc joystick.
Isaac.S

[Myron]

Very cool!.. Ours is s top water job that is similar to an airboat, but it has the camera looking through a clear dome in the bottom and once we get teh funding, the Sonar will be able to see whatever is submerged. Here is a link. There are more pics on page 2..

http://www.rcgroups.com/forums/showthread.php?t=981922

Myron

[isaacs]

I did some playing around in Google sketchup. I am not good at it yet but this is kind of the general design I am thinking about. I am not sure if I'll need the buoyancy tanks on the top. Depends on if I make it neutrally buoyant to begin with. I have read people fill the motors with transformer oil for seals. I am thinking I'll do as well.
Isaac.S

[nick_75au]

Isaacs,
Dont quote me on this but I believe transformer oil is not good for your health or that of the aquatic life. If you can use some form of vegetable oil better or best investigate magnetic couplings, no fluid contact on the motor then. Are you a member of the "homebuiltrovs" forum on yahoo groups, an excellent resource for the info you seek.
Nick