Has anyone had experience with this parallax motor driver?

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BrendanP

Senior Member
I'm looking for a DC motor driver to use with my stock feeder during R&D. It will be quicker to buy something off the shelf until I sort out some other issues with other parts of the proect. I came across this

http://www.parallax.com/Store/Accessories/MotorServoControllers/tabid/160/ProductID/64/List/1/Default.aspx?SortField=ProductName,ProductName

Has anyone had experience with them? One glaring deficiency is that it doesn't give direction control.

I ust came across this which does have direction control, again any comments,advice would be appreciated.

http://www.trossenrobotics.com/store/p/5108-SyRen-25A-regenerative-motor-driver.aspx
 
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MBrej

Member
Hey, that first parallax seems simple enough to use, just send a pulse between 1ms and 2ms to change the speed of the motor. It does have reverse, a 1.5ms pulse is 'stop' and depending which side of this you go, the motor will turn in the corresponding direction, (look at the specification at the middle of the datasheet)

Matt
 
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Wrenow

Senior Member
No experience with that one in particular, though I have been pleased with Dimension Engineering Products (that particular ESC is made by Dimension Engineering) - and they have other products you might find useful as well.http://www.dimensionengineering.com/

From what you have said, it would probably do what you want, depending on the motor you are driving. Do you have any idea what speed and torque requirements are going to be? If not that high not tremendous torque, it might prove simpler and far cheaper to use the Hitec 1425CR "servo" - looks like a hobby RC servo, but has a speed controller built in instead of a servo amplifier, so think of it as a geared motor in a nice mount with an ESC, all for about $16. http://servocity.com/html/hsr-1425cr__continuous_rotatio.html

Servo City also has tons of wigets to give you ways to attach things to the output spline.

Both the Trossen and the Hitec would allow you to control direction and speed with the servo command, and the DE from Trossen allows some other commanding methodology as well.

Just depends on the mechanical needs as to whether either or both would work. Are you more dropping rabit/cat food our of a bin, slinging deer corn over a wide area, or broadcasting large bales of hay?

Cheers,

Wreno
 
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BrendanP

Senior Member
Hi Wrenow, I'm driving a automotive wiper motor, tough,cheap and common.

It's for a automated goat feeder. The motor opens closes a hatch to lets the animals feed but closes back down to stop rain etc. wetting the feed and causing mould growth which will kill stock. I'll eventually draw a pcb including a ESD but for now its easier/quicker to just lash the thing together with off the shelf parts for field testing.

Thanks for the input MBrej.

I'm going to order the http://www.dimensionengineering.com/SyRen25.htm.

This guy has a helpful page on wiper motor hacks http://www.scary-terry.com/wipmtr/wipmtr.htm. He says that a motor can pull 14 amps stalled so the SynRen25 will do that and still have lots of margin or I could I use it latter with larger motors in other projects.

".....Since battery life is proportional to current draw, we can conclude that choosing a SyRen or a Sabertooth for your next robotics project will give you 10-15% more battery life than with other motor drivers. This would result in many more casualties if your robot becomes autonomous and starts crushing humans....."

This is from the data sheets for the device, it was a strong selling point for me.....
 
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Wrenow

Senior Member
Hi Brendan,

Although you could possibly gear down and get by with a smaller motor or a CR servo to lift the hatch, you are probably better off with the wiper-motor (after all, they are designed for a harsh, outdoor environment.

Of course, would not putting a roof over the feeder, and a drain hole in the bottom accomplish much the same thing without as much effort? And, you goat could actually eat in the rain if it were hungry?

For what it is worth, MTroniks, http://www.mtroniks.net/ which is in the UK, has a nice range of ESCs for hobby uses that are waterproof from the factory - they are the favourite of many RC Model Warship captains worldwide (I have been using one for years here in Texas, and they re a staple in Australia, California, Virginia, Maryland, etc. as well). They have several fwds/rev models. And several in the load handling range you are considering.

Cheers,

Wreno
 
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BrendanP

Senior Member
Thanks Wrenow, The feeder is designed to be free standing, it sits out in the paddock with asmall solar panel to power it so I can't really roof it. In any case leaving it open lets birds and rodents get in and eat the food and soil it. Moldly food is lethal to stock. I had a horse eat a piece the size of a quarter mixed in with a bucket full of good chaff and nearly die.

I'll eventually use a DPDT relay with a TIP35C transistor under PWM to control the motor.

Wrenow while I've got you, I have a query re. the operation of servos.

If a servo is under picaxe control and power is removed/lost from the servo and/ or the picaxe and then restored does the picaxe still "know" where the servo arm still is? ie is there feedback from the servo to the picaxe telling the picaxe where the servo arm is on restoration of power?
 
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Wrenow

Senior Member
Brendan,

I know what you mean about mold and livestock, especially horses. Keep in mind though, that it may prove more difficult to keep critters (bugs, rodents, etc.) out of the feed than you think. Simply closing a lid may not suffice.

A bin that drops a measured amount into the trough periodically might perform the same thing you are after, and could be a smaller motor/drive unit.

R/C hobby wervos do know their position. Though there may be some movement on powerup - so if you end at say 25% of the way from the CS wtop, and power down, then power up with a command to the same position, there should, in theory, be little or no movement (though there usually is a tad on initial power-up). When not powered, though, the servo has no "holding" power.

However, on the continuous rotation servos, or a motor with a speed controller, there is no position sensing. Might could use a limit switch to turn off power once the end is reached, or to be sensed by the Picaxe an the motor killed? A pot of some kind would allow a softer closure, as you could slow the lid to a stop.

Good luck,

Wreno
 
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