SNMP Trap test suggestions?

Hey Everybody, I'm trying to use Wireshark to see the SNMP protocol in action. I've hooked up a printer and allow it to run out of paper during a print job. Shouldn't that trigger an SNMP trap transmission? I can't seem to detect it over Wireshark. What's a good way to trigger an observable SNMP trap with a common external device ? Thanks! Dan