[RonaldoNZ]

Well, I've completed my set of eight switches, my machine has two drives in X so i wanted a set of home+limits on both sides of the gantry. Each home/limit pair is joined in series. I designed them to run at 12V rather than 5 to address any potential noise issues and also its easy to tap off 12v from the controllers PSU. I used optocouplers to adapt that voltage to the bob.

I also made them N/C in order to address the inherit safety problem with using an N/O switch, I.E. if a sensor fails or a lead is damaged the opto (which is at the bob end, not the sensor end of the cable run) will go open circuit and trigger a stop. This meant making a little optocoupler bob adapter. The switches themselves have two leds in them, a uv one to show the switch is running/powered at a glance which changes to a red one on trigger. I'm pleased with the results, they do everything I wanted in a tidy self contained way. Here are my circuits and a little story in pictures.

Attachment 201412Attachment 201414Attachment 201416Attachment 201418Attachment 201420Attachment 201422Attachment 201424Attachment 201426Attachment 201428

[john-100]

Hi Ronaldo

the switches look great

your limit switches look like a variation of one of the circuits in post 710
I think your the first to build limit switches with transistors in the limit swich assembly

what BOB do use the opto-isolator AND gate adaptor with ?
just curious because of the volt drop across the two NPN transistors could be a problem with some BOB's or printer ports

John

[RonaldoNZ]

Hi Ronaldo

the switches look great

your limit switches look like a variation of one of the circuits in post 710
I think your the first to build limit switches with transistors in the limit swich assembly

what BOB do use the opto-isolator AND gate adaptor with ?
just curious because of the volt drop across the two NPN transistors could be a problem with some BOB's or printer ports

John

Cheers. The bob is a Chinese generic, an HY-JK02-M 5 axis. It expects 5v dropping to ground, I run the bob off the same 5v supply as the bob side of the optos. I tested the prototype obsessively to work reliably with it, going as far as to set up a bunch of bread boarded units just to make sure. That 5v rail is unaffected by the 12v drop.

Test six times, solder once as they say. :cheers:

[john-100]

Hi Ronaldo

after testing a BOB that looked like the one your using
I ended up tracing the circuit
the BOB I tested had a few errors the first being the + supply pin 14 not being connected !

by now I expect the boards to of been redesigned ,
if not the attached diagrams could be usefull

John

Attachment 201462

Attachment 201464

[Falcon69]

Hi Ronaldo

the switches look great

your limit switches look like a variation of one of the circuits in post 710
I think your the first to build limit switches with transistors in the limit swich assembly

what BOB do use the opto-isolator AND gate adaptor with ?
just curious because of the volt drop across the two NPN transistors could be a problem with some BOB's or printer ports

John

The switches do look great, nice job!

John,

I built some with the onboard transistor as well also. They are hard to see. Surface mount and are between the two LED's and under the Sensor.
Attachment 201502
Attachment 201506



I have that same breakout board. It came with a crappy controller and a read out display. Worst $90 spent. I was advised by Ger21 (i think it was him) in my machine build thread to scrap it and go with the PMDX-126. Which I did. I have not hooked it up yet, as my machine is far from being done, but The quality is far superb over that Chinese board. Plus, it is made to fit the Ethernet Smooth Stepper and PMDX also makes a spindle control for it that plugs right into that 126 board, which I got as well.

I just looked at my chinese board as well, identical to yours RonaldoNZ, and John is right, that pin isn't even connected to a power source. The Via goes straight through the circuit board, but unlike the other two IC Chips, it is not connected to the trace.

Jason

[john-100]

Hi Jason

I missed that change when you last redesigned the sensors !
I'll have to have a closer look !


this picture of the breakout board shows the way I added the +5V link to the first 74hc14 IC :-
Attachment 201514

this wire link will correctly power the IC the limit switches are connected to

without the link the 74hc14 only works (to a degree) because its a low power CMOS device
and a logic high level(+5V) on any input will be connected to its supply pin 14 via the input protection diodes ! :devious:


John

[Falcon69]

Hi Jason

I missed that change when you last redesigned the sensors !
I'll have to have a closer look !


John

No John. These are the single LED's, not the ones in the kit or for the panel mount indication. These only require 3 wires. Ground, 5v Power, and Sensor Output.


I was looking at that board also, but it appears that via has solder mask on it, as well as that trace of course. Need to scrape off the solder mask first, otherwise, he's going to have trouble soldering that wire on.

Another thing, which I can't understand. That board design has gone through several manufacturers and several retailers/wholesalers. I'm surprised that it hasn't been redesigned to include that trace connection and the other things you pointed out. The board you showed has blue solder mask, mine has green, and the silk screening is a little different. That board is a simple design, but to redo it and have a one off board made, would be more expensive than just buying a PMDX-126.

[RonaldoNZ]

Hi Ronaldo

after testing a BOB that looked like the one your using
I ended up tracing the circuit
the BOB I tested had a few errors the first being the + supply pin 14 not being connected !

by now I expect the boards to of been redesigned ,
if not the attached diagrams could be usefull

John

Attachment 201462

Attachment 201464

Fascinating find John! Thanks very much for the traced circuit, great stuff and very useful indeed.

I am getting 2 volts on that pin which as you explain in your follow up post I have just read is why its "running"

A little bit of kynar will fix that, again thanks a ton, great find.

[RonaldoNZ]

No John. These are the single LED's, not the ones in the kit or for the panel mount indication. These only require 3 wires. Ground, 5v Power, and Sensor Output.


I was looking at that board also, but it appears that via has solder mask on it, as well as that trace of course. Need to scrape off the solder mask first, otherwise, he's going to have trouble soldering that wire on.

Another thing, which I can't understand. That board design has gone through several manufacturers and several retailers/wholesalers. I'm surprised that it hasn't been redesigned to include that trace connection and the other things you pointed out. The board you showed has blue solder mask, mine has green, and the silk screening is a little different. That board is a simple design, but to redo it and have a one off board made, would be more expensive than just buying a PMDX-126.

No one in their right mind has a one off board made. Custom PCBs are easy, especially after the first few hundred. You tend to get your workflow sorted. It only makes any sort of sense to get boards made commercially if your planning on making large commercial volumes for commercial ends.


Also a single 1cm piece of wire is considerably cheaper than any replacement board, its a trivially easy fix for a board that works anyway. Personally I'm not a believer in throwing stuff away just because you perceive it to be easier to throw even more money at a replacement. The world has enough landfills already.

[Falcon69]

No one in their right mind has a one off board made. Custom PCBs are easy, especially after the first few hundred. You tend to get your workflow sorted. It only makes any sort of sense to get boards made commercially if your planning on making large commercial volumes for commercial ends.
.

Oh, i know what you're saying. I'm simply saying that if it were to be redesigned, you'd have labor costs, and then can send away the board to manufacture. You can get 10 boards manufactured for 40 bucks off eBay. Then you also have the cost of the components and then the labor to solder them all on. And, if you want to go even further, the cost of either buying a reflow oven or making one for the SMD components.

Obviously making several hundred, or even several thousand boards is more economical. But for an everyday diy hobbyist, that's not feasible, cost wise.

I was just unpleased when I received my board. It just looked so cool when I saw it on eBay and bought it. The thought of having a digital readout display (which isn't really functional correctly with Mach3 anyway) and a mini remote control was cool. But, after I was explained a few other related non-functioning features, and suggested a better board, I decided to go that way. This board, the same one you have, just sits on a shelf now.

[Pleine]

For installation of my limit and home switches, I'd rather glue the milled plexi holders onto the metal of my machine. I am not sure yet about the best places and ways to install the switches, and I'd prefer not to drill holes into my mill for the moment.

Now I am looking for glue that reliably holds plastic (plexi for moment) onto metal (anodized aluminum and painted steel).

Any ideas, recommendations or links ?

Thanks guys !

[dsnellen]

I use hot glue for temporary and sometimes permanent placement of objects. Works fine.

[Jerry Wheeler]

Fascinating find John! Thanks very much for the traced circuit, great stuff and very useful indeed.

I am getting 2 volts on that pin which as you explain in your follow up post I have just read is why its "running"

A little bit of kynar will fix that, again thanks a ton, great find.

Attachment 208194

...added the rest of the circuit with John's fixes- Anybody want to verify the schematic?

[nlancaster]

I have not read all 52 pages of this thread. These look great for home switches. but Not really suitable for limit switches are they? I mean they are normally open if I am reading how they work correctly.

Wait, just found the post #39. the pullup resistor makes it safe. I do not understand exactly how pullup resistors work do I have to do anything to my BOB to make it work?

This is the BOB I have. http://www.cnc4pc.com/Store/osc/prod...products_id=45

[RonaldoNZ]

A pullup resistor at the bob in itself doesn't make it safe, just NC. Your bob has built in selectable pullups which is nice but doesn't help you achieve a fail safe switch.

I.E.
If you have a cable or connector fault in the run to the switch the pullup at the bob will continue to hold the input high (pulled up to 5v) and with no switch to pull it low it will stay that way.

Have a look at my switches at #1015 I designed them so that the NC state is dependent on the switch being powered up and running correctly. They are as a result inherently safe.

[Falcon69]

As promised...

I have posted the Schematic for my switch kits. Since the majority of the design was derived from here and help offered by a few members in the design of this Kit, it should be and will be open-source. All the bugs in the kits seem to have been worked out, and I am now posting the finished results of the schematic.

I have posted in the New Products and Announcement thread for those of you who are interested in saving time and labor and would like to just purchase them instead.

I have also posted the directions, so that may help as well for those who do not know exactly what this kit does.

Enjoy Everyone!

Special Thanks to Romanlini and John_100 in helping with the design of this kit.

Jason

[jm82792]

For your website I went down that rabbit hole and recommend you go with a wordpress website while using Woocomerce.
It's easy, cheap, and the results are professional.

[Robert M]

Jason !! Maybe it's me....but, can't seem to find this thread where your website info are ??
Why not giving your website link here ??....and on your PDF doc ??..
my 2cts advice ! ;-)

[Falcon69]

Hi all!

I have no website just yet. That costs money, and on a student budget right now, it's not feasible. I have posted information in the Product News and Announcement thread, located here for those interested. I'm not allowed to post the information here to sell them.

But I've posted the schematic in post #1030 for those who want to build their own!

If you're wanting to build your own, just prepare a lot of time to make molds for casting the resin for the switches/magnets. Also, allow about 2 weeks to have the circuit boards made. I use a company on eBay called Sitopway, and the boards come out really nice. But, because there are 5 different designs (Mainboard, LED Front Panel, USB Rear Panel, Magnet, and Switch), they will charge an additional $40, as long as all the designs are on one board. I use Diptrace for the circuit board design. It's a free program, up to 300 pins/pads. For this, you will also need a Reflow Oven as the tiny 0603 and 0805 components are just too hard to hand solder. I have posted here directions on how to make one using an ordinary toaster oven. Not cheap to build though.

FYI, the components you can buy from Mouser Electronics. I think they are cheaper than Digikey. Since I stopped buying the IC's from eBay, I've had zero failures so far with assembling the boards. Lesson learned.......DON'T BUY Electronics off eBay! They are just crap IMO.

[LessPaul]

I bought Falcon's kit and installed it yesterday. Here is a video of it in action homing. Once I get my electronics box built and prettied up, I'll show the display board as well. For simplicity's sake, I am using one magnet per axis. https://www.youtube.com/watch?v=s2hST9Aid7c