would the parallax basic stamp work for this?

soxthefox

Hi I am new to this forum and do not know much about Parallax and what their different products do.· I have a machine where first

1 motor lowers an arm
once the arm is down 3 motors start spinning.· 2 of these motors spin in one direction while the other one spins in the opposite direction.
after 10 seconds these motors change the direction of spin so now the motor who was spinning in the opposite direction spins in the same direction as one of the other motors while one of the other motors spins in the opposite direction.
after 10 more seconds these motors switch again and the last motor spins in the opposite direction of the other 2
once this is finished 1 motor will raise the arm
I also have a couple sensors thrown into the mix here.

Now my question, could the basic stamp coordinate all of this or is it limited to running 1 motor at a time?· If the Parallax basic stamp couldn't do this, what could?· If the basic stamp could do this would I need any other hardware/software to program it, or connect it to the motors? I appreciate any help I realize that this is a real noob question.

Mike Green

The answer is "it depends". Some questions:

1) What kinds of motors are these? What controls the direction? What turns them on and off? Does the speed have to be changed?

2) How accurate does the timing have to be? It makes a big difference if we're talking about 10 seconds +- 100 milliseconds vs. 10 seconds +- 10 milliseconds.

3) What kinds of sensors? Are they contact closures as far as a Stamp is concerned or do they involve timing or analog-digital conversions?

Parallax has a long list of tutorial books all downloadable for free from their website. "What's a Microcontroller?" and "Industrial Control" come to mind as good introductions to what you would like to do. Look in their Stamps in Class section.

There are 3 main types of motors used for the sort of thing you're talking about ... servo motors - mostly used for hobby and robotics ... stepper motors - used where precise control of position is important ... DC motors - brushless or brush - these are reversible. They need a position encoder when the position or exact speed need to be controlled.

Parallax sells motor controllers for steppers and DC motors (servos have their own controllers built-in). These handle the power switching including reversing and generally relieve the Stamp or other microcontroller of some of the details of handling the motor itself.

The Stamps can certainly handle running several motors at a time. They're used all the time for handling 2 or 3 motors and a few sensors. Assuming you have DC motors, you will need 2 or 3 DC motor controllers (some handle one motor, some handle two motors). Which one to use depends mostly on the voltage and current required for the motor (see: www.parallax.com/html_pages/products/motorcontrol/motor_control.asp).

You will need a Stamp and some kind of board to use for development like a Super Carrier Board. You might find it useful to get a Board of Education which is like the Super Carrier Board, but uses a little breadboard that you can use for testing, then transfer the finished circuit to the Super Carrier Board. If your PC doesn't have a serial port, you will need a USB to serial adapter. The PC programming software is downloadable from Parallax's website. There are versions available for the MacOS and for Linux as well.

D Faust

If you don't need speed control for the motors, just direction the whole motor control could be accomplished with 4 DPDT relays (to reverse the polarity to the DC motor), two optoisolators, and 4 transitors. You would use the transitors (or·4 extra optoisolators) to control the relays, which would change the motors' direction. One of the optoisolators would be used to cut / provide the power for three of the motors (the ones that run at the same time) and the other for the motor that controls the arm. That would be 6 I/Os. If you could find enough IOs for your sensors, and timing doesn't have to be down to the millisecond then I think a stamp would work. If you are new to robotics, then I would recomend the boe-bot to start from. The book that comes with it does a very god job teaching you the basics. Eventually you will outgrow the stamp and boe, but they are a great stepping stone. The stamp has the most code samples to help you learn about sensors and stuff. If you are interested in using the relays to switch polarity then post and I will write up how it works. What experience do you have?

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