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555 timer pulse every day


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I do have some problems with my assignment in my university.

I have to make an electronic circuit to display day/month/year and one component for people to set.

I intend to create a purse using LM 555 which could purse in every 1 day. I did google every day but still don't know how to do with this. My TA said that if I use 555 to set purse 1 day, maybe there will be a lot of interference so that the signal will be not accurate.

So can you guys help me to handle this problem? It's so so tough to me.

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Hello Neptune


Welcome to the forum.

Please post student related questions in the students forum.


In regard to your question.

The 555 timer operates by means of the RC time constant of an RC circuit. Increasing the resistance and/or increasing the capacitance will lengthen the time, however there are limits to which you can use this type of circuit.

One of the problems is that the 555 itself has an input impedance, and that impedance can change with temperature, voltage and time and this will influence the results. Hence the maximum value of resistance is limited by the stray resistances of the circuit.

Large capacitor values are generally electrolytic. Electrolytic capacitors have a leakage resistance which changes with age, voltage and temperature. This also limits the maximum value of resistance that can be used.


While it may be theoretically possible to make an RC timing circuit (555) for a one day period, the values of resistance and capacitance would probably be impractical to achieve without major problems from spurious resistances.


Personally, I would not use a 555 timer for anything longer than a few seconds.


I would suggest that you explore using a much higher speed oscillator and divider to get the period that you require.


Best regards,

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