G540 and Opto Endstop questions

[dfurlano]

I was wondering if anyone could give some insight on using the opto endstops

http://store.makerbot.com/catalog/pr...d/13/image/19/

with the G540?

The opto endstops require a 5v power supply and output a 0 and 5v signal.

Can this signal be directly used by the G540? From what I have read they suggest a SPST to GND inputs (TTL) but I am assuming they most likely can accept the opto but I cannot find any additional infomration.

Thanks in advance.

Dan

[dfurlano]

Actually I just wired the switch directly into the 25 pin cable and it works fine.

[dfurlano]

Using them as homing switches.

Z Axis



XY Axis



A Axis

[dfurlano]

This is what I ended up with. I found an old analytical instrument that was going to be thrown out and I salvaged the box.

Inside the box I used three power supplies. From the top there is a 12v for the spindle control. Next is the 48v motor supply. And at the bottom I used an ATX power supply for the homing switches and cooling fans.



This is the back I have two plugs on for the motors and spindle another for the homing and fans.



Here is the front from the top of the box. The Gecko G540 then the db25 (under the G540) is the spindle control, to the right is the probe and Estop. At the bottom is the db25 for the homing switches that attaches to a second parralell port and below that are the cat5 connectors to the opto endstops.



Dan

[Mariss Freimanis]

A phototransistor works directly with the G540. Take the emitter to the G540 GND and the collector to any G540 input. No other components are necessary.

Mariss

[Fastest1]

Dan
Nice looking work.

Mariss,
Does this mean a phototransistor could be used for a tach with no other parts.

[Mariss Freimanis]

The opto will switch a G540 input without needing any other components. A practical maximum on/off rate is 1,000 on/off cycles per second. It can pass this information on to the PC and it's up to the program running on the PC to figure out what to do with this information.

Mariss

[Fastest1]

I think this means YES on the using the signal for a tach. I cant imagine needing 1000 times per second sampling for a spindle speed of less than 4-5 thousand rpms, right? Doesnt Mach have this ability to process that signal?

Originally Posted by Mariss Freimanis The opto will switch a G540 input without needing any other components. A practical maximum on/off rate is 1,000 on/off cycles per second. It can pass this information on to the PC and it's up to the program running on the PC to figure out what to do with this information. Mariss

[dfurlano]

Is it possible to hook up 4 homing switches to this configuration. Currently I use port #1 on the G540 as a probe input and a second parallel port for the switches. But the second port is not very robust and after several months of use dies. It would be nice to eliminate the second parallel port.

[dmauch]

Why not put a switch on the probe input to terminal 1. Then wire 3 of the switches to terminals 2,3 and 4. The 4th home switch would connect to the other side of a double pole doube throw switch wired to termional 1. In one position the probe is active and the home switch is inactive. In the other position the home switch is active and the proble is inactive.
Dan Mauch

Originally Posted by dfurlano Is it possible to hook up 4 homing switches to this configuration. Currently I use port #1 on the G540 as a probe input and a second parallel port for the switches. But the second port is not very robust and after several months of use dies. It would be nice to eliminate the second parallel port.

[dfurlano]

Thanks for the suggestion. The problem is that after a tool change I have a macro that homes the machine and the probe is used to set the tool offset.

This question stemmed from a problem I had with the machine that was more operator error than anything else.

When I initially set this machine up with homing switches I was interested to see how repeatable the axis were so I did not set zero at the home positions. Come to find out the switches are very repeatable and there was no need to actually set zero. This machine is dedicated to doing basically one type of operation and I never got around to changing the macro to zero at home.

A few weeks ago I set the machine up to do something very different and I used the G54 offsets and I changed them for what I was doing. I then reset the machine back to its original operation forgetting that I changed the offsets. I have since learned never to change the G54 offsets.

When I homed on the first tool change the machine crashed because the z axis was not at zero in the home position. I hit the estop. Totally pissed off I realized what I did and before I did anything else I changed the macro to ensure when the Z was at home it was at zero.

I then changed the tool and started the macro and the machine took off in the Z and crashed the part. At first I thought I screwed up the macro but nothing was making sense. If I ran a program it worked fine if I homed the machine the movement seemed random.

I then started to think it was the parallel port was not working correctly. I use LPT2 for the homing switches. So I went to the computer store and bought a new parallel port but that did not fix the problem. I then realized that somehow the parallel port address changed for LPT2. It did not change in Mach but in Windows so when I inputted the new address everything worked as expected.

Because of the sequence of events I did not consider the port address changed. Now I know.