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April 29, 2010
The clock circuit above uses seven ICs and 19 LEDs to indicate binary coded decimal time. The LEDs can be arranged (as shown in example above) so that each horizontal group of 3 or 4... [more]
April 29, 2010
This circuit uses the PIC16F628 microcontroller to provide 4 timed outputs that can be programmed from 1 minute to 1 week. An extra 8 bit shift register (74HC164) is used for the 4 timer outputs... [more]
April 29, 2010
This clock timer uses a PIC16F628 microcontroller to display 3 and 1/2 digit time and control an external load. The clock includes a calendar with leap year and optional daylight savings adjustments. The timer output... [more]
April 29, 2010
The circuit illustrates using a 10x10 matrix to sequence up to 100 LEDs with just three ICs and 20 transistors. The two 4017 decade counters control the 10 rows and 10 columns so that one... [more]
April 28, 2010
The 555 circuit below is a flashing bicycle light powered with four C,D or AA cells (6 volts). Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values... [more]
April 28, 2010
This 1.5 volt led fasher runs more than a year on a single 'd" cell and alternately flashes 2 LEDs at about a 1 second rate. The circuit employs a 74HC14 CMOS hex inverter that... [more]
April 28, 2010
Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment. A non-polarized capacitor is placed in series with the transformer line connection to prevent DC... [more]
April 28, 2010
The telephone ring generator shown below generates the needed high voltage from a simple switching mode power supply (SMPS) which employs a CMOS Schmitt Trigger square wave oscillator, 10 mH inductor, high voltage switching transistor... [more]
April 28, 2010
This ring generator will ring a telephone once every 10 seconds. The interval between rings can be lengthened or shortened by varying the value of the 1 Meg resistor. The 70 volt/ 30 Hz ring... [more]
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