Countdown Timer

Thread Starter


Joined Oct 31, 2015

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.


Joined Mar 30, 2015
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:


Joined Aug 1, 2013
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.



Joined Nov 23, 2012
Use a presetable up/dn counter instead,
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.