Delay on circuit unstable due to spike in voltage input

Thread Starter

Byron.govender1

Joined Aug 6, 2017
9
IMG_3089.JPG IMG_3158.JPG Good day
I am building a delay on circuit using ne555 timer chip. I'm unable to get this circuit to work for variable voltage input. I have a 47k resistor connected in series to cap 3.3uf to pin 2 and a 47k resistor in series to pin 6 and grounded. The issue I'm having is that when the voltage input increases from just 12v to 13.5v the time delay is almost is 0s but when exactly 12v is input then only will I get my desired time delay. The reason for the voltage spike is because it's supplied from my vehicle while running and while turned off. How will I get the time delay to be the same at 12v and the same at 13.5v? I will attach pics of my circuit for your perusal.
 

AnalogKid

Joined Aug 1, 2013
8,701
What do you want the circuit to do:

1. When power is applied, the 555 output pin 3 stays low for the delay period, then goes high.

2. When power is applied, the 555 output pin 3 goes high immediately, then goes low after the delay period.

ak
 

Thread Starter

Byron.govender1

Joined Aug 6, 2017
9
What do you want the circuit to do:

1. When power is applied, the 555 output pin 3 stays low for the delay period, then goes high.

2. When power is applied, the 555 output pin 3 goes high immediately, then goes low after the delay period.

ak
Number 1 ideally is what I require but the issue I'm having is that when a higher voltage is input, the delay is period is almost non existent. How can I get the delay period to be a constant through any voltage input to the circuit?
 
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