Dark Ride Robot -- Controller Help

[rogerbobulater]

Alrighty, where to start.

Here is the proposed project. Basically, a large scale rideable line-following robot. I have created a walkthrough haunted house for the last few years but next year I am planning to build a ride through haunted house/garage/driveway/whatever.

The ideal is that the robot/car will track on electrical tape using either phototransisitors or prebuilt line sensors from Parallax and I'm going to use a Basic Stamp II as the brains. The plan is to use two 24 VDC 16.5A (300W) 2500RPM electric scooter motors, geared way,way down to power the car. One motor drives the left drive wheel, another the right.
(For a pic of the proposed vehicle - **broken link removed**)

My major question is about an H-Bridge motor controller to drive the motors. Preferably I would like a dual motor unit, but I dont really know much about them and I can't find one with enough current support on the internet. I ideally would like to reduce the RPM's from 2500RPM to somewhere around 1000'ish with the controller and then chain gear it down from there. I don't know if it will then draw fewer amps or what. I want to be able to atleast control a range between absolute off to absolute on, but would prefer reversability.

I'm not able to weld, but I'm hoping to get a MIG welder and learn after Christmas. As far as I am concerned for weight concerns aluminum is the way to go for the frame. When all is said and done I estimate the car itself to weigh about 120-160 lbs max (includes batteries, frame, motor, seating, and facade), though this is only an estimate.

Anyone who could help me find a suitable H-Bridge, an alternate steering system, or could offer anyhelp with any of the bold points, I would greatly appreciate it. Also, if I have got any skewed views or dead wrong infromation please correct me. Thanks
Justin

 

[bryan1]

Hi Roger,
If you take a look at www.oatleye.com they sell scooter motors and also 350watt speed controllers, I reckon their speed controller will just what you need and they aint all that expensive.

cheers Bryan1

 

[rogerbobulater]

well...

Thanks bryan1. I have visited Oatley in the past and the site is great.

Unfortunatley... that really isn't what I'm talking about. Sure I could get some kind of potentiometer type speed controller, but I'm talking automation, not building a scooter.

I need a motor controller that is capable of recieving electronic input from a programmable logic controller, not a manual throttle device.
If anyone knows specifically about such controllers please help.

Thanks, JK

 

[bmcculla]

I haven't seen any integrated H-bridges that are capable of more than 5 amps. You can buy an h-bridge driver chip and use MOSFETS that are capable of carrying the required current. I've used a h-bridge controller from Linear Technologies that worked great. Check Digikey.com. PWM will let you controll the power to the motor.

Make sure you gear down the motors to the point that they are slow even at full speed. If you have a problem with your control system or your controller resets (don't count on your software opperating perfectly - it never does) high power motors can be dangerous. You might want to build a small mockup and get your software running well before building anything big. Plan for failure - if something goes wrong make sure the robot will shutdown and not run people over. Have a big kill switch that cuts off the battery power - again don't depend on software to do this.

 

[evandude]

you might be interested in taking a look at solid-state relays. perhaps you could build H-bridges out of a number of them...

they are basically just opto-isolated MOSFETs that are often capable of carrying ridiculous amounts of current, and they're already mounted in a nice epoxy package with a huge heat sink back generally. all your motor power connections could be done with simple heavy-gauge wire and ring terminals with the screw posts usually found on large SSR's.

they can be somewhat expensive, but if you shop around you may find some that are affordable enough for what you're doing.

 

[bryan1]

Re: well...

Thanks bryan1. I have visited Oatley in the past and the site is great.

Unfortunatley... that really isn't what I'm talking about. Sure I could get some kind of potentiometer type speed controller, but I'm talking automation, not building a scooter.

I need a motor controller that is capable of recieving electronic input from a programmable logic controller, not a manual throttle device.
If anyone knows specifically about such controllers please help.

Thanks, JK

Eh Roger,
I reckon you hook up the pot to a decent servo that way you can still use a plc or pic to control the speed controller. Just a thought.

In the past when I was looking at robotic sites for large H-bridge drivers I did come across a few sites that explained the innards of the big battle bots basically they use a heap of big current mosfets which developed about 60-100 amps of current but I do remember a note saying be carefull as the parts aint cheap and they pack a lot of punch.
I'll have a look for those sites in a day or so when I have the time but I hope this gives you a direction for your project.

Cheers Bryan1

 

[williB]

Hi Roger,
If you take a look at www.oatleye.com they sell scooter motors and also 350watt speed controllers, I reckon their speed controller will just what you need and they aint all that expensive.

cheers Bryan1

i liked the wing generators , dont know what they ment by three phase though, considering they were either 12 or 24 V..

 

[williB]

Hi Roger,
If you take a look at www.oatleye.com they sell scooter motors and also 350watt speed controllers, I reckon their speed controller will just what you need and they aint all that expensive.

cheers Bryan1

i liked the wind generators , dont know what they ment by three phase though, considering they were either 12 or 24 V..

 

[williB]

oops how did that happen..lol

 

[EET Freak]

The three phase AC voltage created by the wind generator is rectified to the dc voltage either 12V or 24V.