At 12:41 AM 4/17/04 +0000, you wrote: >Design help needed. > >I'd like to take a Selectone ST138 to a maxtrac receiver in a >Desktrac. > >I want it to latch and toggle the output to a 12V relay. So when I >key the >portable with that PL it will close and when I key it the second time >it >will open.
How will you protect it from false triggering on a power outage? Or if you aren't around and somebody pops up and keys down with "your" tone? This is why a lot of hams designed touchtone decoders into their control systems back in the 1980s... But, since you asked how to do it... First get the PL decoder connected to the receiver and working properly. I'm going to leave the hookup to you... See www.selectone.com or www.com-spec.com for details. For an indication, just connect a LED and a series resistor to the decode output and when you have that working reliably you can go to the next step. To get the functionality you want all you need to do is connect a ratchet relay (sometimes called an impulse relay or a one-coil-latching relay) keyed by the PL decoder output. The mechanical design of this type of relay insures that the first pulse closes the contacts, next pulse turns it off. Picture a garage door opener - a ratchet relay controls motor direction and if the ceiling light is on or off. One source of relays of this type is All Electronics, a surplus outfit in Los Angeles. Their web site is at http://www.allelectronics.com and they have a 5-volt ratchet relay at <http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=RLY-640> and a 12-volt one at <http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=RLY-87> If you are an experimenter type, you can find a used high current one at the auto junkyard. Several european cars, Volvo included, use a ratchet relay to switch between high beams and low beams - the trigger switch is a momentary button built into the base of the turn signal lever. Mike WA6ILQ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
