Re: Bowden's BCD clock circuit
- From: Greg <ask@xxxxxxxxxxxxxxx>
- Date: Thu, 12 Apr 2007 13:42:11 +1000
On Thu, 12 Apr 2007 12:07:35 +1000, Greg <ask@xxxxxxxxxxxxxxx> wrote:
I've decided to build a BCD clock and after searching for a circuit
I've decided on Bill Bowden's circuit.
http://ourworld.compuserve.com/homepages/Bill_Bowden/clock.htm
After examining the circuit, though, I'm curious about the circuit
giving a pulse every second. There are two NAND gates attached to the
4040 binary counter which then feed into an OR gate. Am I correct in
assuming that they should be feeding into AND gate to get a pulse
every second? As the circuit stands, I would think it's going to give
a pulse on 0.8 sec and on 0.2 sec, or two pulses per second.
I don't think I explained my question properly. I understand that both
of the NAND gates are outputting high normally and either gate will
only go low when both inputs are high. So once 32+16 goes high one of
the NAND gates will go low and when 4+8 goes high the other NAND
output will go low.
My specific question refers to feeding both of these outputs into the
OR gate. My understanding is that if either one input OR the other is
high the output of the OR gate will be high. So, the OR gate will
pulse when 4+8 goes high or 32+16 goes high. (On thinking about the
specific circuit now, though, when 4+8 goes high it will reset the
counter so that it will only count 12). I think I'm starting to
confuse myself, sorry if it sounds unclear.
Greg
.
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