I am using a 555 chip for a monostable time delay circuit. I am using a trimmer to adjust the delay, which is around 10 mS -200 mS. It works quite well at the longer delays and within tolerable limits the lower I adjust it. However, when I get below 20 mS, the delay occasionally swings down 10 mS or more. It happens every 5-20 triggers, very random.
The circuit is below. I am using a relay to power and trigger the 555 simultaneously at the + and – inputs with a regulated 12v. Could contact bounce be the cause? The relay is producing about 5 mS worth of bounce. I’m also wondering; when does the 555 decide to recognize the input, at the beginning of the bounce pulses or at the last one? I am also using .01uF cap at terminal 5 for possible noise control.
I am using 2.2 uF and 4k values for the 10 mS setting.

The circuit is below. I am using a relay to power and trigger the 555 simultaneously at the + and – inputs with a regulated 12v. Could contact bounce be the cause? The relay is producing about 5 mS worth of bounce. I’m also wondering; when does the 555 decide to recognize the input, at the beginning of the bounce pulses or at the last one? I am also using .01uF cap at terminal 5 for possible noise control.
I am using 2.2 uF and 4k values for the 10 mS setting.
