Alarm Dialer Circuit


Posted on Aug 23, 2012

This circuit dials a stored DTMF tone sequence from EPROM when a control line is taken to 0 V. ICl is a Schmitt trigger oscillator, running at around 2 Hz. It clocks a 4024 binary counter. The counter`s outputs connect to the address leads of the EPROM. A 2716 was used here, but the choice of EPROM is by no means critical. Normally, the counter is held reset by a logic 1 on its reset pin (pin 2). When the trigger input is sent low, pin 10 of ICl goes low, pin 3 goes high, and the reset is removed from the counter. It then begins to clock, incrementing the EPROM.


Alarm Dialer Circuit
Click here to download the full size of the above Circuit.

When moved from address 000000, the data on bit DO of the EPROM changes to a logic 1 and holds the circuit running. The last address should have data 11111110 to reset the circuit to standby.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

VHF/UHF TV modulator
Guitar and bass tuner
Up-Controlled Negative Voltage Converter
Maze Robot
tda7560 4 x 50 watt bridge
h bridge with pwm
Fully Parametric Tube EQ (with gyrators)
DC-DC converter to step up input voltage
Thermistor circuit basic application



Top