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Is there a schematic for the shield, or why won't this thing home.

Hi,

I've been working at replacing my Moshi V4.87 board with this one, and I've discovered that none of the connectors are fitting.

I've manged to force the connectors on, and have the motors and such spinning the way I want them, but I'm having a lot of trouble trying to get the endstops to work correctly.

The endstops on the machine are using an NC connection to GND, which gets broken with the endstop is active.

When I home the machine ($H) it moves the head around a bit, but doesn't actually home, although it must think it has homed as it is happy to move from it's selected spot and return to it.

I can fiddle around fiddle around with the invert settings, and using the status command, I get something that looks like the endstops are working, except for it seems to link the X and Z enstops together, so if X is active, then so is Z, and is X is inactive then so is Z.

This is odd because as you know, there is no Z endstop. There is a pin on the board that is marked as the Z endstop, but if I tie the pin low or high then the board stops responding.

I'm trying to find a circuit diagram for the shield so I can work out what is wrong with the enstops, any idea where I can find it, or over suggestions.

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Hi I will post the schematics here tomorrow when I’m behind my home pc. The x and y end stops are being tied down to ground. The motors will spin to find the home but if they can’t then they stop to prevent doing damage. So it looks like the endstops are not working. Are they mechanical endstops? The k40 comes with hal detectors with 5v and gnd so for mechanical endswitches you probably need pull up resistors (between 2 and 4kohm) tied to 5v. Sofar I have not seen any k40 with mechanical end stops but if it is I wouldn’t be ????!

Hi,

Yes the endstops are mechanical switches.

I thought the pull ups in the Atmega328 where active?

I can't see how adding additional external pullups would help, the carriage never reaches an endstop, so the endstop lines are held at ground by the switches. The carriage would have to activate one of the switches for it to go open and the pullup to have a chance of raising the line.

Hi,

I solved my problem, it was due to noise from the steppers transferring onto the endstop lines and being interpreted as a high.

A couple of 10nF greencaps between the signal lines and earth fixed the problem.

It might be an idea to add these to the board for version 2 of the shield.

Thanks for debugging that issue! I haven’t encountered that issue yet but a great idea to include caps if I ever get to do version 2. Also great to know that some versions have just mechanical end switches. Mine come with hall sensors and its always spot on. This is important when you have to home multiple times with engraving and cutting on one work piece. It needs to line up precisely. Does that work with mechanical end switches? Also there is a setting called $26 in grbl to  limit the noise and debouncing of the switches. It’s set to 250mSec but you could increase that to 350mS. $ settings can be programmed via a gcode sender.

Cheers, Paul awesome.tech

Hi,

No never a problem with repeat-ability, but I rarely rehome after the initial time, unless something undesirable happens like loosing power.

I did  try $26 at the time, but it didn't seem to make any difference, I wasn't shore of it was ignoring small pulses or only started to ignore them after the first one.

+1 on wanting to see a schematic. 🙂

Bugger, I thought I was logged in. That +1 was me!

See the download menu, at the bottom, cheers!

Cheers, Paul awesome.tech

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