Maker Pro
Maker Pro

How can I build a simple counter with a HC393 chip?

mohrr

Jun 20, 2012
1
Joined
Jun 20, 2012
Messages
1
Hi, I am going to be using a counter to take a 5 kHz pulse and bring it down to ~19.5 Hz. I am completely clueless how to begin constructing this circuit, other than the fact that I know that I need to set the clears to zero (ground). Thanks!
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
So you've already worked out that you want to divide the 5 kHz frequency by 256? That will give you an output frequency of 19.53125 Hz.
The HC393 contains two 4-bit counters, each containing four cascaded divide-by-two stages. The clock frequency is divided by 2 at the QA output, divided by 4 at the QB output, divided by 8 at the QC output and divided by 16 at the QD output. Look at the waveform diagrams in the data sheet and you will see how this works.
As you said, you need to tie both CLEAR inputs low, because you don't want to disturb the normal "ripple carry" behaviour of the counters. You need to clock the first counter from your 5 kHz signal, clock the second counter from the last output of the first counter, and take the output from the last output of the second counter. Here's a connection list:
pin 1 from your 5 kHz source frequency
pins 2, 7 and 12 grounded
pins 3, 4, 5, 9, 10, 11 not connected
pin 6 connected to pin 13
pin 8 is your output frequency
pin 14 to +5V with decoupling capacitor to ground.
 
Top