Author Topic: Wiring home switches  (Read 41819 times)

nottingham82

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Re: Wiring home switches
« Reply #75 on: March 05, 2017, 10:29:47 PM »
no you only home 0,0 then tell the software what your maximum engrave-able area is.  So you only need an x zero and a y zero homing.  You can do the extra two but those are called limit switches.  Not homing switches.
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pascalp

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Re: Wiring home switches
« Reply #76 on: March 06, 2017, 12:13:40 AM »
Right, my hardware configuration is only "homing switch" and corresponding parameters.
My engraving area is secured by "soft limit". Using GRBL 1.1, it's rely of the size parameters X and Y ($130 , $131 ) and "soft limits" need to be activated with $20=1 .

The V wheels are the last version send with Eleksmaker A5, they replace the previous white-round.
They are good, except that they are poorly assembled. A spacer is missing between bearings, so when you tighten the wheel, you may easily over-tighten bearings and they act as a "brake" not a bearing. I've noticed this problem when mounting them, but dismantling the wheels could be tricky, so I've take care when adjusting them.
« Last Edit: March 06, 2017, 12:24:44 AM by pascalp »
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Hydroid

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WARNING!!
« Reply #77 on: March 17, 2017, 12:52:38 PM »
quick question sorry for the hijack but have bought these will they work for homing for me ?

http://www.banggood.com/10Pcs-Mechanical-End-Stop-Endstop-Limit-Switch-With-Cable-For-CNC-3D-Printer-RAMPS-1_4-p-1073099.html

WARNING: If you use these switches as supplied, with all three wires connected, disaster will strike! (Switch.bmp photo attached).

I had read this entire thread as I have recently bought a A3 2.5W engraver from Gearbest and had purchased these exact switches from Banggood. I have used these switches before without incident, but always a separate isolated switch per axis - never in parallel as described within this thread.

So, today, I mounted my first switch on the X axis. Because I wanted the LED on the switchboard to light when the switch was activated, I also connected the positive red wire to the Vcc pin of the Nano - a convenient spot to get a positive feed. I connected the switch (X axis) and then set GRBL $22 to '1', and in my case, because the homing direction was opposite to what I needed, I also had to set $23 to '3' to get the X and Y drive going towards Front-Left when I issued the $H homing command....

As I said, I connect JUST THE X AXIS SWITCH (ONE SWITCH) and issued the $H command. The X axis began to move towards the left and it hit the switch and homed out as it was supposed to - and the LED light up as I wanted it to. It then moved away slightly, the LED went out and then the Y axis began to move towards the front as it was supposed to. AS I only had the ONE switch connected, I just depressed it as required to simulate the Y axis getting home. All worked well so I went ahead and mounted the Y axis switch and connected it too. I then manually jogged the head out to the midpoint of each axis and issued a $H command to test out the homing. The X axis again moved toward the left and all looked good.... However, when the X axis switch depressed, the stepper stopped and the laser came on at a low level and I heard the computer 'ding' as the COM port deactivated... ??? What the... Thankfully, because I have done the '1K ohm' mod on the laser signal line, the laser only came on at low power and no burning took place... Then, I noticed that unmistakable odour of burning electronic components emitting their 'magic blue smoke' - In this case, my Nano. I quickly pulled the USB plug but it was too late. I disconnected the switches and plugged the USB in. All I got was a brief pulse of the Nano's power LED but no connection... My Nano is TOAST!

I have been an electronic hobbyist for over 40 years and I broke my own #1 rule. NEVER hook up anything that I haven't tested while being supplied by my current limiting power supply. Had I done this, I would have discovered and rectified the problem without toasting my Nano..

The problem lies with the particular design of these switches and what happens when you parallel them. I drew out the equivalent circuit schematic showing the two switches and the common connections going to the Nano - See attached 'Schematic.bmp'. All is fine until ONE switch "makes" it's limit while the OTHER switch hasn't. I have traced, in RED, the flow-path that occurs from positive to negative when the X axis switch has triggered (at HOME position) while the Y axis switch has not. As you can see, there is a DEAD short between positive and negative. This is what blew out my Nano as not too many chips can stand feeding a direct short to ground...

So, there are two ways to utilize these switches in the parallel configuration talked about on this thread:

The first, don't use the red wire - leave it disconnected and just use the green wire to D9 on the Nano and the black wire to ground on the Nano.

The second, and the one I'm using as I still want the red switchboard LEDs to light, is to MODIFY the switchboard. Circled in blue on the schematic is the section of circuit that needs to be eliminated to prevent a short while still allowing the LED to light. As it turns out, because of the way these boards are made, all you have to do is cut the normally closed (NC) legs off the board's micro-switches (DO BOTH BOARDS) - shown in attached 'Switch-Mod.bmp". A quirk to this mod is that BOTH switchboard LEDs will light when either switch is 'made' but that's OK - I find it makes it easier to see the LED because you now have two that you can look at...

I hooked everything up temporarily and did extensive testing with my Fluke and current limiting power supply and the shorting issue is now gone...

Now, to go and shop for a new Nano... Imagine a Robin Williams imitation: Here Nano, nano... :-)

Regards, John.
« Last Edit: March 17, 2017, 12:58:53 PM by Hydroid »

nottingham82

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Re: Wiring home switches
« Reply #78 on: March 17, 2017, 01:51:41 PM »
You do not need all 3 wires!! you need to wire them as Normally open.  One wire is for ground and then you need to pick the appropriate other wire.  One wire is for normally open and one wire is for normally closed.  Mine says NC and NO and com (similar to yours).  Com is the ground.  The wire that goes to NC does not get connected to anything. This a 2 wire mod. only two wires should go from the nano to the switches. 
« Last Edit: March 17, 2017, 01:52:44 PM by nottingham82 »
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Lob0426

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Re: Wiring home switches
« Reply #79 on: March 17, 2017, 02:02:13 PM »
You can wire NC or NO. You can wire them parallel or separate. You can wire them as limits or home or both. The settings are all available if you want to compile your own firmware from grbl. In none of those cases do you supply power to the switch. Signal and ground are the only wires you ever use!

Some where in there you hit the right switch combo to back feed power to a pin.
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Hydroid

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Re: Wiring home switches
« Reply #80 on: March 17, 2017, 02:14:11 PM »
You do not need all 3 wires!! you need to wire them as Normally open..... This a 2 wire mod. only two wires should go from the nano to the switches.

I never said you needed three wires. What I said was that IF you use all three wires on these switches - with two in parallel - you WILL create a dead short from + to -.

I agree, you only need to use TWO wires, but as I stated, I want the LED to work, so I'm using all three..... with the modification...

Regards, John.

Moonie

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Re: Wiring home switches
« Reply #81 on: March 25, 2017, 08:42:48 AM »
So just to recap:

I have the L7 board. I need to do the soldering thingy to add the switches for my X and Y axis? So got the limit switches also from banggood. The two red wires from both the X and the Y limit switch paired together goes soldered onto pin D9. The black wires (also paired) goes soldered to the ground pin ( I don't use the green wires at all ! Is this correct ? Do I have to do a recompile of the software or wil the T2 software work as is ? ( Running latest software and firmware)

Also does anybody have a link to the "new" V groove black wheels since I still have the old round ones.

Also I took the leap and ordered a Eleksdraw. I presume that the T2 software will not work on this since I see that you have to upload firmware etc ?

Sorry for all the questions but I know nothing about electronics and I live in South Africa so replacing a part normally is a 3 to 4 month excercise ! And I want to be sure I don't screw it up 😀
« Last Edit: March 25, 2017, 02:25:03 PM by Moonie »
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ggallant571

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Re: Wiring home switches
« Reply #82 on: March 25, 2017, 10:32:56 AM »
I would securely glue a header to the L7 and run 30 gauge wire from the header to pin 9 on the backside. Then you can  plug/unplug the CPU board without playing with the home switches. You can wire the limit switches to individual I/O pins if you configure the firmware.
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Hydroid

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Re: Wiring home switches
« Reply #83 on: March 26, 2017, 09:05:05 PM »
So just to recap:

I have the L7 board. I need to do the soldering thingy to add the switches for my X and Y axis? So got the limit switches also from banggood. The two red wires from both the X and the Y limit switch paired together goes soldered onto pin D9. The black wires (also paired) goes soldered to the ground pin ( I don't use the green wires at all ! Is this correct ?

No, if you're using the same switches as I posted a picture of in message #78 above, then leave the two red wires disconnected - You only need those if you want the small red LED's on the switch boards to operate - and you need to do the mod I spoke of or you will create a dead short.

What you want is to connect both black wires together and solder them to a ground point. Then connect both green wires together and solder them to D9.

Regards, John.

Moonie

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Re: Wiring home switches
« Reply #84 on: March 26, 2017, 09:43:22 PM »
John,

Thanx. I wil use the first method since I don't need the LED. So just connect the green and black.

Regards
Gerrit
« Last Edit: March 26, 2017, 09:52:54 PM by Moonie »
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Hydroid

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Re: Wiring home switches
« Reply #85 on: March 27, 2017, 11:52:18 AM »
John,

Thanx. I wil use the first method since I don't need the LED. So just connect the green and black.

Correct :-)

Maverick

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Re: Wiring home switches
« Reply #86 on: October 03, 2017, 01:42:32 PM »
no you only home 0,0 then tell the software what your maximum engrave-able area is.  So you only need an x zero and a y zero homing.  You can do the extra two but those are called limit switches.  Not homing switches.

Once you have homing switches in place, how do you set the maximum parameters in the T2 software? Do these max values stop the machine running further than it can in the X and Y directions ?
Also what settings need to be changed in T2 to enable homing ? I have not yet learned about all the $ settings I keep reading about, are they used to change the direction of homing ?

Thanks heaps!   

Zax

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Re: Wiring home switches
« Reply #87 on: October 03, 2017, 03:10:15 PM »
You enable the home switches from the menu, if you have a standard Eleks style machine you shouldn't need to do anything else.

It isn't necessary, but to set the machine size (which will activate virtual limit switches) just click your machine size or use the custom size in the Sketch pop-up and then click Machine Size in the Settings menu on the laser screen.

Maverick

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Re: Wiring home switches
« Reply #88 on: October 06, 2017, 06:05:53 PM »
Hi guys,

So I have added limit switches, X and Y linked in parallel, to create a circuit between the D9 and ground when "home" is reached, I set $23 to 3, and it homes to the left (X axis) (manaSE at the back of machine) and hits the first switch and stops, it does not pull away, or try to home down (Y axis). What am I doing wrong to get it to home both directions ?

My belt is on the top for the X axis, and I have to have invert X ticked to jog in the right direction, can jog direction and home directions be set differently ?

Thanks heaps in advance !

ThothLoki

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Re: Wiring home switches
« Reply #89 on: October 06, 2017, 06:44:03 PM »
awesome job
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