SMD-12 Application Examples
The Industrologic SMD-12 can be used in a variety of applications. With its contact closure inputs and its RS-232 input and output protocol, it can function not only as a message display unit, but can operate as an up/down resetable counter, monitor contact closures and send their status to a computer, and be a master or slave unit to other RS-232 devices.The following examples show how to make connections to the contact closure inputs and the RS-232 signals on the SMD-12:
- Basic message display with contact closure
- Operation as a counter
- Connecting to a PC serial port
- Slaving a second SMD-12 through the serial ports
Basic message display wiring
Displaying messages with switch or contact closures,Controlling the scroll speed, and
Displaying a "home" message.
Up to 12 different messages can be displayed with switch or contact closures by connecting switches, relays, or other contact devices from the message terminals M1 through M12 to ground.
The rate at which the display will scroll when messages are greater than 8 characters can be selected by placing a switch or jumper from the "scroll speed" terminal to ground.
If you like, a special "home" message can be displayed when no other message is being displayed by placing a jumper from terminal M13 to ground.
Operation as a counter
The SMD-12 will change from a message display to a counter when the "count mode" terminal is connected to ground. A switch or relay can be used to activate this mode to allow changing modes "on-the-fly" during operation.
Whenever the SMD-12 is in the message display mode, it will still recognize changes on the "count up" and "count down" terminals, so that when the mode is changed back to counter mode, the correct number of counts will be displayed. (To clear the count with the "clear count" terminal however, the unit must be in the counter mode.)
Connecting a computer to the serial port
Various RS-232 device can be connected to the SMD-12 to display or monitor messages (and counts when in counter mode).
One of the most common devices to be connected to the serial port will be an IBM-PC or compatible computer. The SMD-12 serial port was designed to easily connect to the 9-pin serial port connector on a PC using a common pin-to-pin, male-to-female 9-pin cable.
Other types of RS-232 connections will require referring to the SMD-12 manual to determine the signals to use and their pin numbers.
Slaving a second SMD-12 through the serial ports
On an SMD-12, all messages displayed in response to a contact closure are also sent out the serial port, (including counter display messages). Messages can also be displayed by sending the message to the serial port.
Using these two features, one SMD-12 can operate as a "master" unit which displays messages from contact closures or serial commands from a PC, and sends the message on to a second "slave" unit, which displays the same message.
To use SMD-12 units in this manner, their serial ports must be connected using 9-pin male connectors with the transmit pin of the "master" unit driving the receive pin of the "slave" unit.
Powering the SMD-12 with DC power
A 12 to 24 volt DC power supply, either regulated or unregulated, and providing at least 400 mA of current can be used to power the unit through the terminal block connections.
Powering the SMD-12 with AC power
A 9 to 12.6 volt AC transformer providing at least 400 mA of current can be used to power the unit through the terminal block connections. A common 12.6VAC step-down transformer is an ideal source of power.
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