AVR-Chat

At 08:28 PM 10/4/04 +0000, you wrote:
>Thanks for your feedback Robert and Dave
>
>The (very) distant goal is to control an injection molding machine
>using just low cost microcontrollers instead of plc's.
>However at this point  just knowing if turning on and off a fan or
>any other low power AC motor is possible and the required components
>to do this, would be a sufficient first step.

Your welcome.  Controlling a fan will be a lot simpler than an injection 
molding machine, but certainly a place to start learning.

I'd be tempted to start with Grayhill I/O modules for this.  They are 
isolated which eliminates a lot of worries.  I know they work well at 
isolating the micro from inductive kick back.

Take a look at

http://embrace.grayhill.com/embrace/Item/ASP/PartsList.asp?CatalogGroupID=ACOutput&GroupDisplayLabel=I%2FO+Modules+%5C+Digital+%5C+AC+Output

You will want modules rated for inductive load, something like

http://embrace.grayhill.com/embrace/Item/ASP/Item-Detail.asp?PartNo=70%2DOAC5%2DL&CatalogGroupID=ACOutput&GroupDisplayLabel=I%2FO+Modules+%5C+Digital+%5C+AC+Output

Make sure you check your current and voltage requirements before selecting, 
and give yourself some margin.  Also since this is relatively high (line) 
voltage make sure you have sufficient spacing and that it's fused (and you 
have a manual off switch to isolate everything).

That will get you started w/o having to worry too much about the 
electronics for the power control, leaving you to concentrate on the 
logical control.  I expect the injection molding equipment itself will 
require something a lot more sophisticated than on/off.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III