74LS90 is not counting

  • Thread starter David lopez
  • Start date
I am trying to use the 74ls90. It won't change it's output. It suppose to count to 9. The input
Pulses come from a 555 timer.
 

Baluncore

Science Advisor
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1. Have you got a 5 volt regulated supply?
2. Have you tied all 9_set and 0_set pins low. Pins 2, 3, 6 & 7.
If you let more than one of each float high it will lock the counter.
3. Which clock are you using as the input from the NE555.
4. Have you tied the output of that counter to the other clock input?
We are not long range mind readers.
Please provide a link to your circuit or;
Draw your circuit diagram and drag it onto your next post.
 
I am using a 4.1 volt supply. is that two
Low?
 

Baluncore

Science Advisor
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It may work on 4.1V sometimes, but you should regulate Vcc between +4.75 and +5.25V.
Use a 7805 regulator to provide the +5V supply from a voltage above 9V.

Vcc above +6 volts can destroy inputs. If it is ever possible for the supply voltage to rise above 6 volts, then you must not connect TTL inputs to the positive rail without a 1k series resistor to limit the damage.
 
A higher voltage does not seem to be
Working.
 

davenn

Science Advisor
Gold Member
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A higher voltage does not seem to be
Working.

Again, as in your previous thread ... I will ask for your circuit and photo of your construction

PLEASE do not again leave us all guessing as we try and help you
 

davenn

Science Advisor
Gold Member
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The input
Pulses come from a 555 timer.

Ohh and since you didn't seem to get your timer circuit working properly
it's no surprise that the counter isn't working properly :rolleyes:
 

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