Product Micro DRO ideal for tiny machines, and embedded cross slide scales

[Nicholas Bull]

Hello all, sorry I haven’t been on here sooner but the kids have been on Easter holiday, although it looks like you’ve worked most of it all out anyway!
A couple of things I will point out (torontobuilder I mentioned this in the email I sent you today) is that the ribbon cable pictured in the (I think rsi) readheads you pictured will be very hard to adapt to other types of connector.
Much more important is the magnetic tape for use with the as5311, the pole length is 1mm/2mm pole pair, the tape linked to above is 2mm pole length/ 4mm pole pair. I think I found a supplier on Ali express who sells it but only in 10mm width which may be fine for your applications but was too big for mine.
The read heads I have made are incremental quadratic, and run on 3.3v.

 

[TorontoBuilder]

Hello all, sorry I haven’t been on here sooner but the kids have been on Easter holiday, although it looks like you’ve worked most of it all out anyway!
A couple of things I will point out (torontobuilder I mentioned this in the email I sent you today) is that the ribbon cable pictured in the (I think rsi) readheads you pictured will be very hard to adapt to other types of connector.
Much more important is the magnetic tape for use with the as5311, the pole length is 1mm/2mm pole pair, the tape linked to above is 2mm pole length/ 4mm pole pair. I think I found a supplier on Ali express who sells it but only in 10mm width which may be fine for your applications but was too big for mine.
The read heads I have made are incremental quadratic, and run on 3.3v.

Welcome to the forum, and this thread in particular.

Yes those are RSI read heads. Also very true in regards to the conversion from one type of connector to another. Pretty much requires an intermediary pcb.

Thank you for pointing out that the AS5311 chip needs a 1mm pole length. I've got a supplier of 10 mm wide tape with 1 mm pole length. What width tape are you using? 10 mm may work for larger machines, but narrower is always better for a universal application.

 

[TorontoBuilder]

Anyone looking to experiment on their own with the AS5311 encoder chip can find 10mm x 1.2mm by 1mm pole length magnetic tape at this link

or this link

 

[Susquatch]

Anyone looking to experiment on their own with the AS5311 encoder chip can find 10mm x 1.2mm by 1mm pole length magnetic tape at this link

or this link

The 10mm tape I got works fine with my 15mm read head. I wouldn't be surprised to find that a 10mm head will work fine with the smaller tape - albeit maybe sensitive to center alignment. Then again, @Nicholas Bull didnt say how wide his tape was.

 

[Nicholas Bull]

The tape I’m using is 5mm wide, and it’s accuracy rating is 8um, it’s really hard to find!

 

[jcdammeyer]

The 10mm tape I got works fine with my 15mm read head. I wouldn't be surprised to find that a 10mm head will work fine with the smaller tape - albeit maybe sensitive to center alignment. Then again, @Nicholas Bull didnt say how wide his tape was.

Is it my imagination or is tape and sensor very expensive? I thought I saw something like $200 for sensor and tape.

Isn't something like this cheaper then?

https://www.aliexpress.com/item/32832040239.html

 

[Susquatch]

The tape I’m using is 5mm wide, and it’s accuracy rating is 8um, it’s really hard to find!

That's a 2:1 ratio for 10mm sensors. You are prolly right about it not working reliably if at all, but I'd still want to try!

 

[Susquatch]

Isn't something like this cheaper then?

Certainly it is. But I think you missed the point of this part of the discussion John. You are not going to put that out of harms way where it doesn't interfere with anything - INSIDE your compound between the dovetailed parts......

The direction of the discussion here is to mill a very shallow slot in which to put magnetic tape and mill a small pocket in the opposing part for a miniature sensor.

 

[Nicholas Bull]

That's a 2:1 ratio for 10mm sensors. You are prolly right about it not working reliably if at all, but I'd still want to try!

Not sure I understand you, the width of the as5311 sensor is only 4.2mm approx, with the “legs” it’s a still only 6.5mm odd.

 

[Susquatch]

Not sure I understand you, the width of the as5311 sensor is only 4.2mm approx, with the “legs” it’s a still only 6.5mm odd.

Sorry Nicholas. You would have had to read many earlier posts to understand what I meant. My bad.

I have tested the Ditron read heads that come with 15mm tape on the 10mm tape that is available in lengths and they seem to work fine. That's a 2:3 reduction in tape width for those heads. So I assume that heads that are designed for 10mm tape would work with 8mm tape because it's a proportional reduction in size. However, I just instinctively feel that they won't work with 5mm wide tape because that it too great a difference.

Those are all wild assed guesses and extrapolations based on my experience as an automotive engineer working on electronic systems and sensors for the first 15 years of my career. I spent the next 15 years working on other aspects of vehicle design and vehicle safety and my last 7 years in senior management. I've been retired for 17 years this June. A lot changes in that time, but my early experience still pollutes my thinking.

I have no plans to dissect a sensor to see how they work or what the tape width tolerance might be. I can only go by chip data like that provided by @TorontoBuilder earlier. I don't pretend to know the exact details. I know enough to have a pretty good idea of how much I don't know.

For me, the interest lies in downsizing the DRO Components so they can be embedded INSIDE the machine structure to protect them and keep the machine exterior tidier.

Again, I'm sorry for being so vague in my original post.

 

[TorontoBuilder]

Is it my imagination or is tape and sensor very expensive? I thought I saw something like $200 for sensor and tape.

Isn't something like this cheaper then?

https://www.aliexpress.com/item/32832040239.html

there are many different grades of magnetic tape, with the price escalating the finer the pole length requirements. Chinese encoders typically use lower resolution pole lengths of 5 mm and 2mm with different read heads made for each pole pitch.

The chip we're looking at requires a pole pitch half as long as the usual chinese high end tape. The equipment that can manufacture magnetic strips with alternating N/S poles at such a fine resolution is expensive as hell.

 

[TorontoBuilder]

That's a 2:1 ratio for 10mm sensors. You are prolly right about it not working reliably if at all, but I'd still want to try!

The width of the tape is not crucial, the sensor has a requirement for the orientation of the magnetic strip, and the airgap between the magnet and the AS5311 casing should be maintained in the range 0.2mm~0.4mm. The strip itself can easily be 10mm wide. The development board from them is designed with mounting holes set at 11 mm apart, to accommodate a 10 mm strip between them.

The narrower strip width IMO would only be to minimize the impact on a tiny machine component.

 

[jcdammeyer]

I already have enough in my Mouser Shopping basket to get free shipping so I think I might just order one of these to play with.

https://www.mouser.ca/ProductDetail/ams-OSRAM/AS5311-TS_EK_AB?qs=Rt6VE0PE%2FOfQFCqoE7AuPw%3D%3D

At $21.74 it's not that expensive. If anyone on the island wants one let me know. Also in the next week or so I will be travelling to the mainland; Coquitlam to be specific.
Then I just need to order some magnetic tape I guess. I have two of these in box #42.

DRO-550 | shumatech.com

www.shumatech.com

https://www.micro-machine-shop.com/OpenDRO%20Supplemental%20Guide.pdf

 

[TorontoBuilder]

I already have enough in my Mouser Shopping basket to get free shipping so I think I might just order one of these to play with.

https://www.mouser.ca/ProductDetail/ams-OSRAM/AS5311-TS_EK_AB?qs=Rt6VE0PE%2FOfQFCqoE7AuPw%3D%3D

At $21.74 it's not that expensive. If anyone on the island wants one let me know. Also in the next week or so I will be travelling to the mainland; Coquitlam to be specific.
Then I just need to order some magnetic tape I guess. I have two of these in box #42.

DRO-550 | shumatech.com

www.shumatech.com

https://www.micro-machine-shop.com/OpenDRO%20Supplemental%20Guide.pdf

I posted a few links for the 1mm tape... not the cheapest.

BUT in future if there was demand the price can be as low as about $28 /meter purchased in 50 bulk rolls

 

[jcdammeyer]

I posted a few links for the 1mm tape... not the cheapest.

BUT in future if there was demand the price can be as low as about $28 /meter purchased in 50 bulk rolls

Well there is this where 1m is $66:

https://www.aliexpress.com/item/1005004985633578.html

and this where 1m is $21.56:

https://www.aliexpress.com/item/1005002822394450.html

They don't seem that different both 10mm wide.

 

[TorontoBuilder]

Well there is this where 1m is $66:

https://www.aliexpress.com/item/1005004985633578.html

and this where 1m is $21.56:

https://www.aliexpress.com/item/1005002822394450.html

They don't seem that different both 10mm wide.

check again...

Your second link you need to change selection to 1000mm from 100mm to get the 1 meter price.. $66 bucks on sale. Normally 122

 

[jcdammeyer]

check again...

Your second link you need to change selection to 1000mm from 100mm to get the 1 meter price.. $66 bucks on sale. Normally 122

View attachment 33719

oops. I thought I had ticked that box. My apologies.

 

[TorontoBuilder]

Well there is this where 1m is $66:

https://www.aliexpress.com/item/1005004985633578.html

and this where 1m is $21.56:

https://www.aliexpress.com/item/1005002822394450.html

They don't seem that different both 10mm wide.

I dont think that the first selection is 1mm pole length either it is 5mm.

read the fine print... it states 1, 2, 5, and 10 mm standards are available but does not say which is for sale under this listing. Additionally the model number given is often used on 5mm pole pitch tapes for sale eslewher

 

[TorontoBuilder]

oops. I thought I had ticked that box. My apologies.

no problem.

aliexpress is designed to be confusing and make comparisons difficult.

 

[jcdammeyer]

Like I need another project...
The CPU cooler was a bit bigger than I imagined. With the CPU cooler mounting frame on the motherboard the mounting area inside the used Case interfere. So I have to do some surgery. Which means adding a DRO to my lathe is slipping further down. But I will continue to watch the progress here.