Hi. I am referring to this thread: https://forum.allaboutcircuits.com/threads/monostable-555-trigger-release-issues.113131/
Particularity to post by @crutschow :


In my case, output will not time out. Maybe the reason is because I have a 1uF cap & 300kO resistor, instead of 22uF & 47k, so the pulse windows is too short? I am using the same diode 1N4148, TLC555 (cmos) timer, SW-520D ball switch, and output is going to a mosfet. What could be the reason and what are the possible alternatives?

 

n my case, output will not time out.

Are you using a 0.1uF cap and 100kΩ resistor at the trigger input (pin 2) as shown?
Is the 0.1uF cap polarized?

 

Are you using a 0.1uF cap and 100kΩ resistor at the trigger input (pin 2) as shown?
Is the 0.1uF cap polarized?

Yes I am using exactly this size of elements. 0.1uF cap is not polarized

 

Yes I am using exactly this size of elements. 0.1uF cap is not polarized

Then I expect a wiring error (or less likely, a faulty component).

 

Then I expect a wiring error (or less likely, a faulty component).

I see. So it has to be polarized. So even if I use following setup, the short pulse width actually doesn't matter? It must only change ceramic cap for a electrolytic one?

 

So it has to be polarized.

It must only change ceramic cap for a electrolytic one?

No, there is never a requirement for a capacitor to be polarized.
Here is is better that the trigger capacitor e non-polarized, as you have.

Did you check for a wiring error?

 

No, there is never a requirement for a capacitor to be polarized.
Here is is better that the trigger capacitor e non-polarized, as you have.

Did you check for a wiring error?

I went through and everything looks normal.

 

I went through and everything looks normal.

Then the only thing left is a faulty part.
Is the 470uF capacitor polarity correct?

 

You said the charging capacitor was 1uF but the schematic shows 470nF.
Which is correct?

Can you measure the voltage at pin 2 using a multimeter with the button continually pressed?

 

I see. So it has to be polarized. So even if I use following setup, the short pulse width actually doesn't matter? It must only change ceramic cap for a electrolytic one?

No. It doesn't have to be polarized.
Try connecting a 10nf cap from pin 5 to ground.
Also connect 100nf cap across supply pins.

 

You said the charging capacitor was 1uF but the schematic shows 470nF.
Which is correct?

Can you measure the voltage at pin 2 using a multimeter with the button continually pressed?

1uF, but I am planning to use 470nF later.

Voltage is fluctuating from 1.2 to 2.4V

I now found the cause. Motor vibrations are disturbing the ball-switch, causing re-triggering. Is there a way to soften it?

 

No. It doesn't have to be polarized.
Try connecting a 10nf cap from pin 5 to ground.
Also connect 100nf cap across supply pins.

Like this? Polarized 100nF?

 

I now found the cause. Motor vibrations are disturbing the ball-switch, causing re-triggering. Is there a way to soften it?

To put another capacitor in parallel with a ball-switch will probably not be enough to eliminate the noise? Or? If, what capacitor would you suggest and if it has to be combined with resistor? Thank You

 

To put another capacitor in parallel with a ball-switch will probably not be enough to eliminate the noise?

It should.
Start with about 1µF in series with a 10Ω resistor across the switch.
Increase the cap size if needed.

 

In series? Not like this?

 

You mean this?

 

Like this? Polarized 100nF?
View attachment 303478

Add reference designators (R1,R2,C1, etc.) to all components so we can communicate changes easier.
470n, 100n, 10n are non-polar.

The 2k resistor in series with 470n is not needed.

Not all TLC555 can be used with supply of 3v.
What is the suffix for the TLC555 part number you are using. It should TLC555I.

 

You mean this?

No.
Put a 10Ω resistor in series with a 1µF capacitor.
Connect that across (in parallel with) the switch.

 

No.
Put a 10Ω resistor in series with a 1µF capacitor.
Connect that across (in parallel with) the switch.

Should C1 capacitor be polarized? Can I use a 30Ohm resistor instead of 10 (thats all I have home)?

 

Add reference designators (R1,R2,C1, etc.) to all components so we can communicate changes easier.
470n, 100n, 10n are non-polar.

The 2k resistor in series with 470n is not needed.

Not all TLC555 can be used with supply of 3v.
What is the suffix for the TLC555 part number you are using. It should TLC555I.

Done. C1 as a timer cap is supposed to be polarized, isn't it?