Meet the New DRO Adapter for Glass Scales

[ycroosh]

Over the last few months I've been working on re-designing the DIY DRO Adapter for Glass Scales, and after a few interations it's finally ready for the "prime time". My ini motivation was to replace the HC-05 module. Those are not sold by any regular parts suppliers, so a few times a year I have to contact "my dude" on eBay, ask him to set up a special listing, and then hope that his chinese supplier sends the actual hc-05.com modules and not some knock-offs. That said, the replacement ESP32 chip ended up being a giant upgrade. It has hardware quadrature decoders, sor I was able to get a full factor of magnitude better performance out of it, so here are the highlights:

• In my testing I was able to get the board to handle four axes moving simultaneously at 100,000 pulses per second (equivalent of 5-micron scale moving 500mm/~20" second (it could probably go faster, but my test fixture maxed out at 100KHz)
• The board can handle tachometer input between 0.5Hz and 40KHz (over 40Khz it looses precision, but doesn't crash)
• Position refresh rate is now bumped to 25 times per second, with worst-case "lag" of 0.042s (42 milliseconds).

As far as the features go, it's almost the same as the old adapter, with one notable addition: the board has inputs for four limit switches (one for each axis). Those can be used to set up home position for the machine. I can foresee two scenarios. The most common would be to use a set of proximity switched at the extremes of the axis travel. Another approach that requires compatible scales would be to use the scales "zero" mark Between the two, the board will be able to simlate the functionality that you would get with a [really expensive] nambe-brand DRO that uses scales with a zero mark or a zero region.

The pcture below shows the board with the press-fit harness kit. If interested, you can find mor details here: Wireless DRO Adapter for Glass and Magnetic Scales V2

Finally, it's now 25% less expensive for the kit that includes press-fit connectors, and 33% less expesnive for a kit with standard D-Sub connectors.

I'm working on an enclosure for the board as well, but that is still a few months out. Getting pre-made enclosures is insanely expensive and the board is a but too big for a practical 3D-printed box, so I'm looking at laser cutting the box.

Hope you like it

Regards
Yuriy

 

[Hard_ware]

Ordered a unit just now, and have a 150mm and a 250mm optical linear scales ordered as well from ebay.

 

[Joe in Oz]

Hi Yuriy. Can you please explain how this adapter is connected to the Bluetooth transmitter, or is that on the board (and I don't recognise it)?
I have some old Heidenhain glass scales. Would they work with this setup?

 

[Hard_ware]

On the board. Look to the right of the silver square you can just barely see the antenna pc trace.

 

[ycroosh]

Hi Yuriy. Can you please explain how this adapter is connected to the Bluetooth transmitter, or is that on the board (and I don't recognise it)?
I have some old Heidenhain glass scales. Would they work with this setup?

Joe,
The rectangular silver part is the BlueTooth module (and the main processor).
I'm almost sure the old Heidenhain scales will not work. They likely output sine/cosine waves, instead of quadrature, and need special interpolation cicrcuit to convert to quadrature.
Thank you
Yuriy

 

[Hard_ware]

Do you have the model of the Heidenhain scales, some do output square wave output. But they don’t use a db9 connector which can be fixed.

 

[Pierre52]

It would be helpful if you provided links to compatible scales on your website. Not all of us live in the US so links to either ebay or Aliexpress examples would be good.

 

[ycroosh]

It would be helpful if you provided links to compatible scales on your website. Not all of us live in the US so links to either ebay or Aliexpress examples would be good.

Pierre,
In short, 99.9% of the modern Chinese Glass and Magnetic scales are supported (you can find them on eBay, AliExpress, etc.)
I don't really have a way to test/confirm compatibility with older scales, etc. so it's going to be up to the scale owner to dig up any documentation and see if they are 5V quadrature or not. I get 2-3 emails per day asking if a particular scale or sensor is compatible, and I physically don't have time to research every one of them.

This is the excerpt from the TouchDRO page (if it helps):

This TouchDRO adapter supports a vast majority of Glass and Magnetic DRO scales on the market that output 5-Volt quadrature signal. This includes virtually all Chinese DRO scales from brands like Easson, Ditron, Sino, and many others. The majority of modern scales from well known western DRO brands are supported, as long as they provide 5V quadrature output. This includes most EMS (Electronica Mechatronic Systems) magnetic scales, many Accu-Rite scales, etc.

To determine if your scales are supported, look for the pinout diagram or pin descriptions in the scale's manual or spec sheet.

• If there are pins labeled +5V, 0V (or Ground), "A" and "B", the scale outputs a single-ended quadrature signal. Additionally, if there are pins marked A' and B' (or alike), the scales output a differential quadrature signal.
• Scales that have pins labeled "Data", "Clock", "En", etc. are not compatible, as are the scales that require a negative power supply or power supply exceeding 5V.

Hope this helps
Yuriy

 

[axa88]

As far as the features go, it's almost the same as the old adapter, with one notable addition: the board has inputs for four limit switches (one for each axis). Those can be used to set up home position for the machine. I can foresee two scenarios. The most common would be to use a set of proximity switched at the extremes of the axis travel. Another approach that requires compatible scales would be to use the scales "zero" mark Between the two, the board will be able to simlate the functionality that you would get with a [really expensive] nambe-brand DRO that uses scales with a zero mark or a zero region.

Yuriy, could you point me to an explinaiton or better yet a video of this kind axis limit switch in use. When i search this nambe DRO i find nothing.
thanks

 

[JFL4066]

It would be helpful if you provided links to compatible scales on your website. Not all of us live in the US so links to either ebay or Aliexpress examples would be good.

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