DTMF to Relay Contact.
I originally put this device togther when I was installing a new
microwave link. This is an offshoot of my A-Tone decoder.
The far end was a distant site and I wanted a way of exercising alarms
from the local site to the distant site. The alarms were things like
Tower lights On/Off, Generator On/Off, Door Open/Closed and so on.
For the local site, I generated DTMF tones using my Laptop PC, sound
card and Comtekk software and pumped
this into an unused Audio channel on the link. The far end received the
tones on the unused audio channel and generated the contact closure
simulating the alarm. I was then able to check the far end alarms at
the local site on the dispatch console. This saved a lot of running
back and forth between the sites.
Later, I found a rather novel use for it and thats checking the valves
on my irrigation system. The device is hooked to the irrigation system
and the audio input is plugged into the earphone jack of a HT. I walk
around the yard with a second HT and for zone one, I send a DTMF
1 digit. Check the sprinkler heads then send a DTMF D digit to
disconnect it. Then go to the next zone and so on. I am at times
the envy of my neighbors.
Now, its a Sunday, and what do you do when you want to add a seven
segment display to the gadget right now and you dont have a BCD to
Seven Segment decoder?
Make one, program a PIC and add it to the above device.
DTMF Tone to Relay
BCD to 7 Segment