Home Switch Problem

[m_c]

Does the voltage change when you work the switch?

[Kev2960]

I don't have a manual for the bob just for the machine itself. ive enclosed some photo's of the bob and the main board

[john swift]

Hi Kev

the photo of the breakout board is not close enough to read the lables for the connectors

is this correct ?


also does this 24V DC LED indicator light ???


John

[Kev2960]

Hi John sorry for the delay in replying iv'e just got in from work. The top photo of the bob you've labeled is correct, and the led is lit when powered up

[RickyTerzis]

Hi...as per my knowledge when the limit switch is closed, the EL817 opto isolator's NPN transistor will ground the printer ports input pin. The breakout board does not have any pull up resistors to ensure a printer port input is at a valid logic high when the limit switch is open.

assembly circuit

[Kev2960]

It drops to about 2.8 - 3.0v

[john swift]

Hi Kev

the voltage drop on the printer port pin to 2.8 - 3V is too small

you should have it dropping to near 0V when the switch closes

assuming the opto-isolators LED is powered from +5V
this is what I'd expect for the breakout boards limit switch input

corrected diagram


(arrow pointed to the wrong end of the 1K resistor on the original diagram)

John

[Kev2960]

Sorry my mistake, misunderstood what you said the voltage when the switch is presses is zero volts

[john swift]

Hi Kev

do you use two seperate power supplies for the breakout board ?

I have made a correction to the diagram in post 12
this is how I expect the breakout boards input circuit to be



from the limited detail in the photo of the breakout board the two regulator IC's appear to be LM317 plus resistors = 5V regulator for the 74HC245D IC's

LM2576S switching regulator = 10V regulator for the analogue VFD drive

John

[Kev2960]

Hi John. There is a 24v which I think is for fan and 5v which is for the drivers. I've been playing around with it all night but still no joy. Just a silly question but should the switches be carrying voltage ? Because mine aren't