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Originally Posted by arpus maximus
Wow! Thanks for all the replies! Perhaps a little background information on my project will allow for some more detailed advice:
I, along with two friends, are converting a full-size car (an '87 chevy nova) into a remote control car. The nova has an automatic transmission and power steering.
We need to work on 3 elements: 1) the gas, 2) the brakes, and 3) the steering.
For the gas, we have a small 5V servo hooked via PWM cables into the robot controller. This servo pulls the gas line, and works well; no troubles here!
For the brakes, we will use a larger, 12V motor (probably a globe motor) hooked up to either a worm gear or, more likely, a sort of rack with teeth... I don't know what it's called or how else to describe it. This will push the brakes. Preferably this motor can spin in both directions, but we COULD automatically return it to the initial off position via a spring.
For the steering, we will again use a 12V motor. This motor needs to turn both directions.
We will most likely draw power from the car's battery, possibly through the cigarette lighter outlet.
The robot controller we have is the FIRST robot controller from a few years back... perhaps the 2001 edition. I am not entirely certain. It has 5V output and 16 pins. It uses PBASIC.
My plan for the larger motors is to use victors. joystick forward will activate the servo on the gas line, joystick back will operate the 12V globe motor on the brakes, joystick left/right will operate the 12V globe motor working the steering wheel.
Does anything about this plan sound bad? Are there any glaring errors? Again, Thanks so much for your continued assistance!
ARP
EDIT: Oh, and our budget is minimal. The three of us pay for everything right out of our pockets, so cheap is good!
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well, first of all, you were describing a whats called a rack and pinion for the breaks.
Next, If you are using that FIRST hardware, you are all set to go for 12V motors and speed controllers. The FIRST robot controller (FRC) outputs 5v to other things like speed controllers and victors that handle the 12V motors. The 5v circuit is just between the FRC and the controller while the 12V circuit is between the speed controller and motor. Just look at some of your schools robots and you will get the picture.
Im assuming you got the FIRST equipment for free, but if you really want to do it cheaply, you could probably get some electric RC hardware from a hobby shop or online, transmitter receiver, giganto-monster servo (at least RC plane-wise) and then two speed controllers to run the larger motors for steering and breaks all for like $200 ish
Sounds like a cool idea. Not so much for originality (its been done before) but because you sound like you are going to do it pretty simply and easily. Maybe i should try it out
As for potential problems, a globe with the stock gear box almost defenitley does not have enough torque. Second, i'd be surprised if the servos you were talking about for the gas line had enough force, but if you tested it, i guess so.
Lastly, have a lot of fun, join your schools FIRST team, and... uhhh.... have the letter 'M' stricken from the alphabet