Automation Controller Board Help!

[Cartierusm]

I don't know if I even have the right forum but I'll give it a shot. I'm going to be building an automation machine. I'll try and explain the function of the switches and if someone can help to tell me how to build/buy/program this sort of thing I'd appreciate it or at least where to start.

The function would go something like this:

A main rocker switch would turn the unit on and immediately would turn on Switch1 and Switch2 > The Operator would press a momentary button then the controller board would perform the following function > Switch3 would turn on a motor when the motor hits limit Swtich4 the controller turns off Switch2 and turns on Switch5 and Switch6 > when limit Switch7 is hit the unit stays in it's current position for 1 minute > then Switch8 and 9 are turned on returing the motors to their original position hitting more limit switches and then Switch3 is turned off and the unit stays until the momentary button is pushed again.

Now that is the simple version of basically switched turning on and off by other switches and a timer at one point. The ultimate would be an LCD Display to control the speed of the motors and the time the motors stay in position after they reach their limit switches, this would mean a built in speed controller (a digital voltage variac?). It would also have a few fail safes, so when it's first turned on it waits until certain parts to come up to temperature by use of a thermistor to a set tempertature and then the momentary switch would light up telling the operator to perform the function.

As I said any help would be appreciate, any idea or direction would be helpful as I have no idea where to go. I don't neccesarily need to build it myself, although I'm pretty good with electronic fabrication, just not design or programming, I can make boards and such. Thanks.

[Cartierusm]

OK no responces, oh well. I've figured some of this out. I've bought a kit to play around with a Parallax Stamp Discovery Kit and I'm already learning the program.

So what's everyone's opinion for this kind of microcontroller?

[Al_The_Man]

If you just want point to point moves and minimum operator input, i.e. push buttons - limit switches etc, then a PLC might be an ideal way to go.
It has all the inputs and outputs conditioned already. e.g. opto's and relays etc.
Some even have motor controller outputs rather than using simple on/off outputs.
For design from scratch the PicMicro site has lots of application notes and free design software for PIC implementation.
There is also a PIC tutorial page here:
http://www.winpicprog.co.uk/
http://www.winpicprog.co.uk/pic_tutorial.htm
Al.

[keebler303]

A PLC would be a good "professional" way to go. If you are looking for something cheaper, a microcontroller with some extra circuitry would give you about the same functionality. I've never dealt with PLC programming, so I don't know the ins and outs of it but I do play around with some PIC microcontrollers and have been pretty satisfied with the results. It will definitely take time to develop all of the external circuitry to keep the microcontroller safe from the world.

If you are making only one and want it cheap, the microcontroller way may be better. If you are making a bunch, a PLC will let you get things done much quicker. Once one is working, you just have to program the rest and all the relays and conditioned inputs are already there ready for you to hook up.

The choice really is up to you, you know what your skills are and what the project is.

Good Luck
Matt

EDIT: I use Hitech C for programming www.htsoft.com They have a free development environment (hitide) and a free version of their compiler. I use a Pickit2 for programming and I have been very happy with it so far.

[Jim G]

One other thought would be simple relay logic.

Going the pic route would be far more complicated than necessary.

PLC's use relay ladder logic to create the program. Pretty easy to use and develop.
Automation Direct has low cost PLC's. I have installed several in punch presses for an air solenoid controller that have hundreds of thousands of cycles on them.
They would certainly do the job, but again, adding greater complexity than is probably necessary. (Much easier to develop than a pic system though.)

With just relays, you could get time-delay relays that initiate from:
Delay on Break
Delay on Make
Interval (actuation switch makes it cycle on and off.
and other special purpose functions.

Then use cube relays for the rest.

Regardless, the first thing to do is create a flow chart.
Once you know exactly the functions to be carried out, you can divide out the inputs/outputs and delay functions to create the relay ladder.

Hope this helps,
Jim

[Cartierusm]

Thanks Keebler. I think I'll go with the Parallax Stamp as I can get a real good one for about $50 new on ebay. That way if I ever need to upgrade the machine I can do so without having to add more circuitry as I've already started to learn how to wire and program in. But I'll looking what you're talking about to see the similarity. What MCU do you recommend I start looking at?

[keebler303]

So you know, The pickit2 programmer is something like $40 and the compiler and development environment are free. The chip depends somewhat on the compiler you are using. The hitech C 'lite mode' compiler (the free version) will program all 10,12,16 series PIC's. I would recommend a chip with an onboard oscillator to simplify the board.

Right now I am really into the PIC16F88. Onboard oscillator, Analog to digital conversion, USART (for serial port). The current project is using one to measure an analog voltage and report that to the computer via rs232. Pretty neat stuff!

You might want to look into some chips with more i/o pins if you have a lot of switches, buttons, and such. For example the 16F877A has almost 30 i/o pins.

I don't really know about the parallax stamp so I can't really give you a comparison.

Matt