Countdown Timer

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Orbitingful

Joined Oct 31, 2015
32
Hi,

I am going to build an alarm that will have 4 7-segment displays. 2 for the hours and 2 for the minutes. I will use 4 4510 ICs along with 4511 decoders. I have figured out how the counting up will work. I will reset the tens collumn of the minutes and hour once it reaches 6. However, I was wondering, how I could make 6 the maximum number when counting down.
 

dl324

Joined Mar 30, 2015
8,918
Post a schematic.

You'll need extra logic to handle carry when tens minutes has counted down to zero and use the load function.
 
Last edited:

AnalogKid

Joined Aug 1, 2013
8,103
Basically, a borrow signal from the more significant digit upstream is used to load a 5 (not 6) into the counter. This circuit will be very difficult to discuss with a schematic that has a unique reference designator for each component.

ak
 

GopherT

Joined Nov 23, 2012
7,983
Use a presetable up/dn counter instead,
@Orbitingful
The pins P1, P2, P3 and P4 are presets. You can tie each to Vcc and ground to set to 5 (or) 6. You will have to experiment. You need the carry-in/carry-out to trigger the Pin1 to toggle low/high to cause the I think it needs to be tied to a binary 6, that way it outputs a binary 5 when the carry-in/carry-out grabs the Preset value when needed.
 
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