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test instruments projects
BH4534A frequency counter schematics Low cost 5 ½-digits frequency counter

The BH4534A low cost frequency counter is a funny project based on vintage CMOS Philips integrated circuit HEF4534B and some other CMOS 4000 integrated circuits. The counter has maximum range of 3.7 MHz, common cathode LED display and power consumption about 60mA at 5V DC.
If the counter is powered at 12V, the frequency range is around 10 MHz. More digits can be easy added before or after HEF4534B.

The HEF4534B is CMOS 5-digit counter LSI circuit with multiplexed tri-state outputs and terminal count output. Unfortunatelly, it has no clock enable input and so an external gate must be used.

As frequency standard is used clock crystal 32.768 kHz with CMOS 4060 oscillator/divider with additional CD4027 flip flop circuit. The circuit produces 1 Hz gate signal and 2048 Hz scanning clock signal for LED multiplexed display.