help!! 24 secs counter using JK(7476) 555timer 7segments and ic7447

GopherT

Joined Nov 23, 2012
8,009
Is it critical that these chip are selected? Otherwise, you could feed your 555 into a BCD counter, to create a 4-bit 0-10 value. Then feed that binary value into a seven-segment decoder. That give you the first digit.

To get the tens digit, get a second pair of BCD counter/7-segment decoder. For this one, the 555 timer does not drive it, instead there is a divide-by-ten output on the first BCD counter that drives the 10's digit BCD counter.

You can cascade as many as you want.

To reset (or stop) at 24, you can use a hex inverter chip and an 8-input AND gate. the goal here is to create a signal that can control the 'disable' pin on the first BCD counter (prevent it from counting even though the 555 continues to pulse.

Look for CD4510 and CD4511 chips if you want to go old-school. I don't remember the 74-series equiv.
Tie the reference inputs to binary 24 (high or low as needed), and then
 
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