Thumbwheel Switches
zxninja,
Sorry I didn't get back to you about your other questions. I've been out in the country mowing, trimming and building display racks. I only have phone modem internet connection out here. Much slower than the broadband connections I use in town, so don't get online much.
Ron answered your thumbwheel question much better than I could have....Thanx Ron.
I had a project several years ago in which I had to inform the shipping office clerk which one of 24 shipping lanes was blocked or jammed. This had to be done on a shoestring budget so I could not purchase something like a HMI. All I had was a 1771 12 to 120 VAC output card (would have been simpler with a TTL output card). I powered the outputs with a 12 vac transformer and then built a perfboard circuit to convert each of the 12 vac output lines to 5 vdc signals (tiny bridge rectifiers and 5 volt zener diode for each output line). These signals were connected to IC's (BCD to 7-segment divers) This only used 2 7-segment displays and the PLC program would detect the jammed lane then flash the appropriate digets to inform the shipping office clerk. The clerk could then page the shipping lead to clear the jam. This sytems worked very well for several years, until we built a new shipping building with sixty-six shipping lanes and dock doors. this project of course had a big budget and I got to set up some Panelview systems to track jams, fulls and product flow conditions.
Ron's information on the LED Displays is right on also.
Thanx Dan