# How to make a chess clock using 74LS193? 5minutes down-counter

Thread Starter

#### exia1277

Joined Aug 13, 2020
4
can u guys help with the general idea on how to make one? pls

#### ericgibbs

Joined Jan 29, 2010
13,585
hi exia,
Welcome to AAC.
Do you want a two player Black and White clock.?

E

#### schmitt trigger

Joined Jul 12, 2010
463
For any project, you have to perform a divide-and-conquer approach:

Divide: you have to divide the project into its logical blocks. What I see in this project is
1) An accurate timebase
2) Down counter
3) Binary to BCD conversion
4) Output display

#### schmitt trigger

Joined Jul 12, 2010
463
-For the accurate timebase, you could use a 32.768 Khz tuning fork with a 15 bit binary counter

-For the down counter you could use the 74193 but have to figure out the gating to pre-load 300 seconds. Since in binary this is 0001 0010 1100, you need 3 down counters.

-If you want a geeky project, you could directly display the binary representation and have the players to decode the binary values in addition to playing the game. But don't think your players would like to do that. So you would require to convert the raw binary count into a 3 digit BCD while also converting to the 60-count based seconds display
-Finally, the BCD value convert it to a 7 segment LED value.

Overall, I would say that you are looking at over 20 IC packages, if you would like to do it with SSI ICs.

Thread Starter

#### exia1277

Joined Aug 13, 2020
4
hi exia,
Welcome to AAC.
Do you want a two player Black and White clock.?

E
yes sir/mam

#### dl324

Joined Mar 30, 2015
13,082
yes sir/mam
Do you want it to count down seconds from 300 to 0? Or do you want it to display minutes and seconds?

I doubt that you need a very accurate time base unless it's a tournament and you need accurate results between sets of players.

Do you want one timer being stopped to start the other timer?

Why are you using LS193? They're expensive and power hungry compared to CMOS.

I think an Arduino Uno/Nano would be a better solution.

Thread Starter

#### exia1277

Joined Aug 13, 2020
4
-For the accurate timebase, you could use a 32.768 Khz tuning fork with a 15 bit binary counter

-For the down counter you could use the 74193 but have to figure out the gating to pre-load 300 seconds. Since in binary this is 0001 0010 1100, you need 3 down counters.

-If you want a geeky project, you could directly display the binary representation and have the players to decode the binary values in addition to playing the game. But don't think your players would like to do that. So you would require to convert the raw binary count into a 3 digit BCD while also converting to the 60-count based seconds display
-Finally, the BCD value convert it to a 7 segment LED value.

Overall, I would say that you are looking at over 20 IC packages, if you would like to do it with SSI ICs.
Do you want it to count down seconds from 300 to 0? Or do you want it to display minutes and seconds?

I doubt that you need a very accurate time base unless it's a tournament and you need accurate results between sets of players.

Do you want one timer being stopped to start the other timer?

Why are you using LS193? They're expensive and power hungry compared to CMOS.

I think an Arduino Uno/Nano would be a better solution.
5minutes or 1 minute will do

#### ci139

Joined Jul 11, 2016
1,696
(the 555 --or-- double T --or-- even the digital RC oscillator would give you exact enough time base)

? what is your display
• single/double digital LED as for "there is yet time remaining" and "the time has passed"
• analog micrometer converting output count to voltage by DAC
• binary led display
• 7-seg led display
• other

Thread Starter

#### exia1277

Joined Aug 13, 2020
4
(the 555 --or-- double T --or-- even the digital RC oscillator would give you exact enough time base)

? what is your display
• single/double digital LED as for "there is yet time remaining" and "the time has passed"
• analog micrometer converting output count to voltage by DAC
• binary led display
• 7-seg led display
• other
7 segment led display

#### dl324

Joined Mar 30, 2015
13,082
7 segment led display
Unless this is a school assignment, an Arduino Uno will be a more compact solution.

Two 3 digit counters will require more than a dozen IC's (6 counters, 6 decoders, and some glue logic).

#### ci139

Joined Jul 11, 2016
1,696
sure it's not the ls192 you want to use . . . tough it makes no difference for the tens of seconds count . . . or maybe it does if we assume 0 to be 10(5) ... 2(1) and 0(0) -- takes one ls74 to implement this <- the 5' digit goes then with the same "logic" -- so 3x '192 + 1x '74 + some controls . . .
. . .
Bad magic :
// it's possible to stretch/elongate the $$\overline{R}$$ pulse if there will be such need
// also the "double" clock generator may be implemented by various different means
// -- this one uses the SN7400 transistor model not the LS variant one - anyway -
// - the gates do not have too precise V.threshold value so it must be adjusted experimentally each time

Last edited:
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