Pager motor driver/controller project question (and intro)

[beaker]

Hi all,
My name is Rick, I work at Smooth-On, Inc as a technician... you have probably run into our products in one way or another... we are entrenched in the movie industry as well as concrete, home hobbiest, manufacturing and everything in between... so with that being said, if anyone ever needs help molding, casting, Life Casting, rubber, silicone, or resins I would be more than happy to help... I know that stuff VERY well... electronics? not so much, thus the reason I am here... I have an idea using a pager motor but I need to build a small circuit that has some kind of random sequence (or at least simulated random) to make the motor spin faster, slower, pause, surge... not even sure if it is possible... I want to be able to activate it with a single throw switch... just looking for some direction on where to start... electronics always facinated me and I tried several times to begin the hobby but have not been able to find a medium to start... any help would be much appreciated!
Thanks

 

[beaker]

no replys because it isn't feasible or is it a typical noob question that people are tired of fielding... I don't mind doing my own research and it really can be more simplistic than this, I just don't know where to start with anything electronic... I have zero experience...
anyway,
thanks for looking at least

 

[Resqueline]

I don't know why no-one jumped in on this one, maybe the heading was uninspiring. I was away on a trip myself and had little time for internet access.
This sounds like a task for a microcontroller. I'm quite sure someone here will be able to give some suggestions on where to start. I'll edit the heading a little.

 

[(*steve*)]

No replies, because nobody replied I guess. I remember seeing this when you posted it, but I was too busy to craft a reply. I'll fix that now

I built a kit many years ago that used a laser and several motors each with slightly tilted mirrors mounted on them to produce pretty displays. Each of the motors changed speed in a "random" manner. The final motor doing exactly what you want -- speeding up, slowing down, stopping, and reversing.

I would love to point you at the project, and give you information about how to get the circuit diagram, but I fear that finding the actual device at the moment would be almost impossible A search of the most likely on-line resources to find out where it was published also drew a blank

However the circuit, as I recall applied a random number of pulses to a 4017, with each output determining some function -- some were speeds, and one toggled the motor's direction. Another part of the circuit limited the rate of change of the motor's speed, so that the change in "speeds" often effected a change in the rate of change of motor speed.

Now, that's all quite complex, and it's not the way I'd do it today. The easiest way is to use a microcontroller with PWM output to control the motor speed and have some form of randomness detected by the uC which determines what it will do next.

It is also possible to create a pseudo-random sequence, but this is something that will repeat over some time period (are there any uC's with random number generators?).

A PICAXE chip is an easily programmed uC, and easily fast enough for what you require. The stuff for programming it is either very cheap or free, and there is a reasonably large community of people working with them (and generally very happy to assist beginners).

The source of randomness may be the hardest thing. Actually, it won't! The PICAXE has a command RANDOM that returns a pseudo-random number.

So all you need is a program to make the motor do as you want.

It could be something with this structure

initialize speed and direction

repeat
. . get a random time
. . get a random speed
. . decide whether to change direction (low probability)
. .calculate difference between current and target speed (change direction means sign changes too)
. . for i = 1 to 10
. . . . newspeed <- oldspeed + increment/10
. . . . if sign changes reverse motor direction
. . . . set speed to absolute value of newspeed
. . . . oldspeed <- newspeed
. . . . delay 1/10th of delay time
. . next
until 1 = 0 (i.e forever)

(edit: dots there just to force indenting)

It will be a little more complex than that, since that isn't the language the PICAXE uses, but it's *A* way to approach the issue.

In hardware, you'll need an H bridge to allow you to change motor directions.

And of course you'll need a power supply. Remembering that the PICAXE wants 5V and your motor may run from a different voltage.