I am working on a lie detecting and right now im working on a pulse beat monitor. I would like to display the beats per minute on a dual 7 segment display. right now im using a 74161 counter and a 4511 7 seg decoder. my problem is that right now it counts up to 15. is there a way i can get it to count and hold beats per minute or will i need an 8 bit counter? another thing is getting it to hold a certain value how could this be done? right now im just counting a clock from a 555 timer but it just resets and starts all over again. Any one with help it would be appreciated!

 

You're using a syncronous binary counter which can hold values in the range 0 to 15 and you want the display in decimal digits. There are at least three ways to convert from 4-bits binary to two digits decimal.

1. Decoding ROM (Read Only Memeory)
2. Decoding PLD (Programmable Logic Device) or FPGA (Gate Array)
3. Microcontroller

The 74161 has enable inputs and you hold the present value by taking one or both of them inactive.

I would suggest that you consider two decade counters and use BCD to 7-segment decoders designed for that purpose. Now the useful range is 00-99

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I would suggest you go for option 2 or 3 as your counter and decoder can be both exist on one low power chip rather than several power hungry TTL ICs.

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Ok guys i will give that a whirl. thanks a million