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Help with sequential relay timer.

Andy_Mac

Dec 8, 2017
1
Joined
Dec 8, 2017
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Hi all, I'm looking for some help to build a simple 4 relay sequential timer. Its going to connect to an old style mobile phone via soldering to the keypad contacts to make a basic GSM autodialer. I run a fox rescue group and this is gonna save me hours watching cage traps. I have some basic electronics knowledge and know I can do this with 555 timers but I could do with some help on working out a basic circuit that will give me a short pulse on each relay output to simulate three key presses on the phone, ie screen wake, speedial number, call. It only needs to work once so no need for any auto reset and it needs to work from a Microswitch that will close and stay closed when the trap is triggered. From what I've been reading the 555 needs a timed pulse which would be a problem. Any help would be greatly appreciated.
 

AnalogKid

Jun 10, 2015
2,922
Joined
Jun 10, 2015
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2,922
The phone might not like having only a few milliseconds between when one switch input is released and the next one is activated. What about something like this:

Microswitch closes
first relay energized for 0.5 sec.
1.0 sec. wait
second relay energized for 0.25 sec.
1.0 sec. wait
third relay energized for 0.5 sec.
circuit pauses until power is cycled off and on

???

If so, a better approach is to use a CD4017 Johnson Counter. Outputs 1, 4, and 7 drive relay driver transistors. A 555 or part of a CMOS gate for the clock. What is the power source voltage, and how long might the circuit have to remain powered up on one battery charge?

ak
 
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