Hi Albert,

I did what you suggested and it has made absolutely no difference...???

 

Hmmm....
If you keep the trigger switch closed for a long time does it keep counting or does it stop after the initial two counts?

 

I'll try in the morning and let you know. Thanks

 

I think i know why it is all over the place.

The points on the bottom of the clicker press trigger i am using to take the input from are under voltage when the machine is powered up.

The clicker press has a double handed button system, you have to press the left button and then the right button for it to punch.

readings i have taken:

When press is on - right hand trigger contacts 19.6v
When right hand button is pressed 0v
When left button is pressed on its own the voltage on the right hand trigger drops to 14.1v
When both buttons are pressed 0v.

How to can i overcome the voltage going through the contacts so it just detects the click of the button?

Pics of the bottom of the switches and the inputs i am using:

 

How have you connected these switches to your circuit?
Are you connecting to just one switch or both?
As the switches have 14V - 19V on them and you do not want to connect such voltages to the '555 what circuitry do have between the switch contacts and pin 2 of the '555?

 

With the 2 contacts circled in the pics.

Only connected to the right hand trigger


And I have nothing in between the circuit and pin 2.

What do I need?

 

With the 2 contacts circled in the pics.

Are those two terminals connected to anything else in the machine (whether the button is pressed or not)?

 

Hi Albert, sorry but I have no idea where they go, cannot easily see

 

Hi Albert, sorry but I have no idea where they go, cannot easily see

But do those terminals have wires connected to the machine as well as to your circuit?

 

Yes the pics are without my circuit connected. I am just piggybacking on top of the existing wires

 

And the voltage between those terminals when the button isn't pushed is 14V or 19V depending on whether the Left button is pushed?
And when the right button is pushed that voltage is 0V?
And your circuit is, and is going to be, powered by a 9V battery?

If that is right then you do need some circuitry between that button and your circuit. Please confirm the above then we can think about what that circuitry might be.

 

Hi Albert, Yes the above is correct. Thanks

 

With the power off, can you check whether either of those terminals is connected to the mains earth?

If it is then having your circuit connected there will be safe. If there is no earth connection then having your circuit isolated from those terminals would be desirable but more complicated.

 

Hi Albert,

None of the connections on the bottom of the clicker press go to ground unfortunately...

 

OK. So the simplest way is to draw some current from those terminals. We need to know how much we can draw without upsetting the machine. Can you connect a 12k resistor across the terminals on the right button and measure the voltage across the resistor with the left button pressed and make sure that the machine still works correctly with the resistor connected.

That resistor will draw just over 1mA if the voltage is still 14V and that is enough to work an opto-isolator.

 

ok will do, will have to be in the morning as my resistors are at home.

 

I was also thinking could i not just connect a NC SPST relay to the trigger to give me a signal pulse on my circuit?

 

I was also thinking could i not just connect a NC SPST relay to the trigger to give me a signal pulse on my circuit?

The relay coil will draw a LOT more than 1mA and would probably pull down the voltage when the switch is open enough to upset the machine.

 

oh ok thanks.

 

Morning Albert,

With the resistor connected it now reads 15.6v on the right terminals which then drops to 11.2v when the left button is pressed.

The press also still operates normally