Re: Conveyor Belt
I can?t draw pictures and post them, but here is a basic description of the control circuit you have in mind:
</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Let the foot switch be a ?momentary contact type.? That is, the switch is closed only when your foot is on the pedal.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Place that momentary contact switch in series with a control relay.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Place one ?a contact? of the relay in parallel with the momentary contact switch. That way, once you hit the switch with the foot pedal, the relay will energize, and the ?a contact? that is in parallel with the foot switch will close. This will keep the relay energized, even after you lift your foot from the pedal. It is called a ?seal in? feature.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Place another ?a contact? in series with the starting coil for the motor. Thus, when the relay is energized by the action of the foot pedal, the motor will start running.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Now you will need some type of sensor, such as those suggested by sdbob and steve66, to detect the fact that the item has left the belt. All you need to do is to have a ?b contact? from that sensor in series with the relay I mentioned above. When the sensor sees the bottle leave the belt, the ?b contact? opens, the relay no longer has power, and the motor stops.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Note also that the action of the ?b contact? removes the ?seal in? feature, so that the system is ready to start up again the next time you hit the foot pedal.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">
SIDE NOTE:
I used the terms ?a contact? and ?b contact.? Some of you would know these instead by the terms ?normally open contact? and ?normally closed contact.? It is a personal preference, but I seriously dislike the ?NO? and ?NC? terms. They tend to open the doors to miscommunication. For example, if a motor is intended to be run 24 hours a day, 7 days a week, and 365.2475 days a year (i.e., including all the Feb 29 days), would you say that its main contactor is ?normally? closed, on the basis that the normal condition of the system has that contactor closed? I would not. That contact is ?normally open.? To avoid that confusion, I would call the contactor by the name ?a contact.?