Problem with homing repeatability. Possible digital noise

Hey guys.

So the other day I switched out my mechanical switch for a hall effect sensor to see if that would fix my homing repeatability issues, but it didn't. It's consistently ~0.1-0.3mm out each time I home it.

I've also tried changing the home search speed and that doesn't seem to make a difference. However I opened up the halscope to check the axis.0.home-sw-in and when it's within ~0.5mm or so it'll toggle between True and False. The closer to 0mm it is the less it seems to bounce between the two states.

Would debouncing help solve this problem? If it does, how do I go about implementing that on pin15 on my BoB.

I looked up the Doc for debounce but it doesn't seem very helpful.

Cheers

Update:

I've managed to add debounce to the input pin, however it doesn't seem to be helping. around 80% of the homing attempts it'll go back to 0.

Is there any way to increase that repeatability?

Can you describe the hardware/mechanics of the machine. Can it be possible that are the mechanics and not the software part?

I'm not sure if it will help, but you could try slowing down your homing accelerations, particularly the second and final one to prevent overshoot.

Settings are in the INI file.

When incremental jogging back and forth it'll generally be accurate to around 0.03mm which is more than fine for my needs. But when homing it could be 10 times out. Up to 0.3mm so I believe it could be the home switch.

I've tried setting it to a dead slow search and even then it might be out. Sometimes (Not always) it'll say "home switch inactive before start of backoff move"

AppleAssassin wrote:

I've tried setting it to a dead slow search and even then it might be out. Sometimes (Not always) it'll say "home switch inactive before start of backoff move"

The error message sounds like your home switch is not staying engaged for the full duration of the homing sequence. I did experience that. Are the actuators you are using long enough to stay engaged while it coasts to a stop?

rodw wrote:

AppleAssassin wrote:

I've tried setting it to a dead slow search and even then it might be out. Sometimes (Not always) it'll say "home switch inactive before start of backoff move"

The error message sounds like your home switch is not staying engaged for the full duration of the homing sequence. I did experience that. Are the actuators you are using long enough to stay engaged while it coasts to a stop?

Well I've tried using both Mechanical switches. The relatively cheap lever arm roller type and a hall effect sensor. Both show the same problem

Thanks

But you have not answered my question.

I've switched back to a mechanical switch, this time rather than wiring it for Normally Open, instead wiring it for Normally Closed.

I'm not sure why this made a difference, however now I'm within 0.01mm repeatability for every homing operation.

I'm not sure whether the first switch I used was faulty, and whether there was too much noise / wrong resistor value used for the Hall sensor. Whatever it was. Switching out the switch fixed the issue