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| Stumped about my Hall effect limit switches |
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| billbyrd1945:
In an attempt to dump mechanical limit switches, I installed 3 Hall effect sensors as shown below. When a magnet is passed over the individual sensors, its relay indicator lights up and the normally closed relay breaks the circuit to kill the appropriate axis. This works, but... Each limit switch works so that it stops the travel of that particular axis and requires a reset to continue with its travel. If you fail to move that axis after resetting it, the other two axes will run passed their stops even though their individual relays are triggered. This might make it easier to envision what happens: Scenario 1: Y hits a limit and stops. I reset it and move it again to make sure it was reset. Then I test X. It hits a stop, I reset it, test to make sure it travels. Ditto for Z. Scenario 2: Y hits a limit and stops. I reset it but I DON'T jog it to test for a reset. Then I test X. It passes its magnet, lights up its relay, but continues to travel without setting off an alarm, eventually crashes. The breakout board and just about everything else is eBay components marketed as "Longs", Chinese stuff. I've tried for a couple of days to figure it out but I'm stumped. Any ideas? I appreciate any help. Diagram attached. |
| thm_w:
So there is 5V and Ground going to each limit switch, and an individual line coming back from each. Seems good. With a multimeter test switch output signals when multiple are active, you may be able to do this on the PC as well depending on how the board is hooked up. Some hall sensors may not work at 5V, so we want to eliminate the possibility of supply being too low. So whats left is the logic running on the PC or control board, to determine what happens when a limit is hit. Typically these are wired in series, and XYZ are all one limit switch. Is it possible the controller logic is seeing you "override" all limit switches? Therefor ignoring future input? You should never be hitting a limit switch and continuing with it active, you'd generally tap it and move off for homing only. edit: I don't think that relay board is necessary, usual probe will have NPN open collector output, so can go straight to the logic input (which would be pulled up on the board). That said it should not be causing any serious issues. |
| SilverSolder:
Where is the "reset" performed... on that board, or somewhere else? Does the board have any logic / CPU on it? Maybe a picture of it would be good? |
| Doctorandus_P:
Throw away the Longs board and use something like GRBL ? GRBL has been ported to a lot of different uC's. The original "arduino" boards are maxed out on CPU capacity (both speed, peripherals and FLASH). I've been using a port to the Blue Pill for some time, and it has plenty of room for some extensions. It also uses hardware USB (CDC, none of that RS232 translator chip rubbish) |
| billbyrd1945:
I'm listening to each of you and using my pea sized brain to interpret what you ask and suggest. Last night I removed the relay pack and wired it up as shown in the attached pic. It was a total fail. When the Hall effect sensors are triggered (or when they're not) the axes jog as if the sensors weren't even there. |
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