Precision time-countdown timer


Posted on May 15, 2012

The circuit uses an ICM7213 precision one minute/one second timebase generator using a 4.1943 MHz crystal for generating pulses counted by an ICM7217B. The thumbwheel switches allow a starting time to be entered into the counter for a preset-countdown type timer, and allow the register to be set for compare functions. For instance, to make a 24-hour clock with BCD output the register can be preset with 2400 and the EQUAL output used to reset the counter. Note the 10 k resistor connected between the LOAD COUNTER terminal and ground.


Precision time-countdown timer
Click here to download the full size of the above Circuit.

This resistor pulls the LOAD COUNTER input low when not loading, thereby inhibiting the BCD output drivers. This resistor should be eliminated and SW4 replaced with an SPDT center-off switch if the BCD outputs are to be used.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

565Sca-demodulator
Frequency to Voltage Converter Circuit Schematic Diagram
HV SUPPLY METERING & OVERVOLTAGE TRIP
ir remote control extender mark 5
Eliminating Ground Loops
TDA9813T TDA9813T VIF-PLL With QSS-IF And Dual FM-PLL Demodulator
Custom Fan Controller
Electronic Watchdog



Top