Automatic power switch
Posted: Mon Nov 18, 2013 4:12 pm
I just bought an automatic power switch for my 2/70 mobile unit in the van. It is probably the most useful thing a mobile ham could have. No more dead batteries due to a radio left on.
http://www.aprsworld.com/apo3/
Basically this thing is a voltage-controlled switch with a timer and a relay after it. The “trigger voltage” can be set to 11.8, 12.1, 12.7, 13.05 volts DC and the timer to 0, 5, 10, 20 minutes (0=immediately). Both are set by DIP switches.
On shutdown, when the trigger voltage is reached (say, after you turn off the vehicle), then the timer kicks in. Once the timer times out, it cuts power to whatever’s connected to the output.
I got this a few months ago after I took the FT-8100 out due to a problem it was having, intermittent no tx/rx on 2m. (Don W7MRI's bench was the last stop on it’s way to the dumpster.) The 8100's display shows the voltage briefly when turned on, and occasionally I’d crank the engine with the radio already on. Sometimes the dip in power was so great that it would cycle power to the radio. On those times, the display would show between 9 and 11 volts, not good for a radio.
Don later told me it can run just fine from 9 – 15 volts. He found that the VCO was out of tune (and fixed it), but he never did find out what caused it. Best guess is the add-on tone decode board was pushing against the VCO.
With the radio now back in my van, this auto power off thing is set to trigger at 12.7v and the timer for 10 minutes. So, 10-15 minutes after I turn off the engine, the radio turns off. When I get back in and start it, the thing waits until voltage has risen above the trigger level, then turns power on immediately. I don’t need to touch a thing to turn the 8100 on or off!
http://www.aprsworld.com/apo3/
Basically this thing is a voltage-controlled switch with a timer and a relay after it. The “trigger voltage” can be set to 11.8, 12.1, 12.7, 13.05 volts DC and the timer to 0, 5, 10, 20 minutes (0=immediately). Both are set by DIP switches.
On shutdown, when the trigger voltage is reached (say, after you turn off the vehicle), then the timer kicks in. Once the timer times out, it cuts power to whatever’s connected to the output.
I got this a few months ago after I took the FT-8100 out due to a problem it was having, intermittent no tx/rx on 2m. (Don W7MRI's bench was the last stop on it’s way to the dumpster.) The 8100's display shows the voltage briefly when turned on, and occasionally I’d crank the engine with the radio already on. Sometimes the dip in power was so great that it would cycle power to the radio. On those times, the display would show between 9 and 11 volts, not good for a radio.
Don later told me it can run just fine from 9 – 15 volts. He found that the VCO was out of tune (and fixed it), but he never did find out what caused it. Best guess is the add-on tone decode board was pushing against the VCO.
With the radio now back in my van, this auto power off thing is set to trigger at 12.7v and the timer for 10 minutes. So, 10-15 minutes after I turn off the engine, the radio turns off. When I get back in and start it, the thing waits until voltage has risen above the trigger level, then turns power on immediately. I don’t need to touch a thing to turn the 8100 on or off!
