Unusual 7 segment display

Thread Starter

adriano08

Joined Apr 25, 2010
33
Hi guys. :)

I just made a 60 seconds counter using 7 segment display. The problem is whenever I turn off the power and switch it back on, it will always start counting from 24 onwards instead of 00... and so on.

Why is it so and how to make it count starting from 00 whenever I power up the circuit?:confused:
 

CoolBeer

Joined Mar 29, 2010
40
I think the answer is on page 42 in the datasheet!

Seriously though, unless we know what you are using to drive the 7segment all our guesses will be kinda foggy, so shed some light on the situation if you please :)
 

Thread Starter

adriano08

Joined Apr 25, 2010
33
I think the answer is on page 42 in the datasheet!

Seriously though, unless we know what you are using to drive the 7segment all our guesses will be kinda foggy, so shed some light on the situation if you please :)
I was using 74HC4511 and 74LS90. All connections are pretty correct. Also, 5V to power up, 270ohms to limit the current for the common cathode segment display.

Hmmm...:rolleyes:
 

Thread Starter

adriano08

Joined Apr 25, 2010
33
Unless you post a schematic of your circuit, we have less of a clue than you do.
Hi there. :)

Schematic wise I have not make one yet.:p The 60s counter works normally counting from 00 to 60. But it will always start to count up from 24 onwards whenever I power up the circuit. After that it becomes normal until I restart the whole set up again..

:rolleyes:
 

JoeJester

Joined Apr 26, 2005
4,390
Schematic wise I have not make one yet.:p The 60s counter works normally counting from 00 to 60. But it will always start to count up from 24 onwards whenever I power up the circuit. After that it becomes normal until I restart the whole set up again..
Did you wire this up or is it a manufactured circuit?
 

Thread Starter

adriano08

Joined Apr 25, 2010
33
Did you wire this up or is it a manufactured circuit?
I patched up on my own. :)

Update from here:
I proceeded to 4 digits counter. Everything works well. However there are some concerns again.. Whenever I supply voltage to circuit, the digits will randomly appear and then start counting from there instead of counting from 00.00 onwards.

So how to make it goes 00 whenever I turned on the power supply 5V?:confused:

PS: Normal typical counter wiring up using 74HC4511 and 74LS90
 

Thread Starter

adriano08

Joined Apr 25, 2010
33
You probably do not have a power on reset function. Plus mixing 74LS and 74HC logic can be problematic - http://www.massmind.org/techref/logic/family.htm
I see sir. How do I implement the reset function? I mean I wanted to get count from 00.00 onwards whenever I power up... but not when I power up, press reset button then it will be 00.00.

On a side note, why mixing 74LS and 74HC can be problematic? Or any suggestion of ICs can be use with 74HC4511 because I just bought it and do not want to waste it.

:confused::)
 

Thread Starter

adriano08

Joined Apr 25, 2010
33
Another question, is diode necessary to be connected? Currently I did not connect any diode in the circuit. I thought of current flowing backward when the power supply is turn off. Is this logical?:confused:

If yes, where should I normally place the diode?

Thanks. :)
 

beenthere

Joined Apr 20, 2004
15,819
Currently I did not connect any diode in the circuit. I thought of current flowing backward when the power supply is turn off. Is this logical?
No, it's not even possible - unless there is something in the circuit we are not aware of.
 

Thread Starter

adriano08

Joined Apr 25, 2010
33
I have dismantled everything and came out with a sychronous counter. The problem no longer occurs. ;)

Ripper counter really a mess for me.

If there's any more problem encounter, I will ask you guys.

Thanks.:p
 
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