DIY DRO read heads?

[ChrisBParticipant @chrisb35596]

[ChrisBParticipant @chrisb35596]

So in my long list of tools I need for my mill and lathe, a DRO for each is on the top of the wish list, unfortunately having bought a fair share of tooling lately, spending the best part of €1000 is a bit out of question for now.

I'm after a 2 and 3 axis DRO with magnetic heads, so after sifting through the forum and other sites I came across Yuriy's toys TouchDRO adapters which seem good for my application. Now I still need the read heads, and at around €150ish each, needing 5 of them with shipping etc, its still a bit on the expensive side.

I came across this website which have these magnetic read heads : **LINK**

Would these be any good? At €30 each they are considerably cheaper than a ready made read head, granted there will be lots of work to machine a housing for the read head and cables and connections, but I still recon it will work out much cheaper….if they are any good that is!

[Les Jones 1Participant @lesjones1]

The statement " Resolutions from 0.244 µm " is not clear. Is that the highest resolution or the lowest resolution ? If that is the highest I would not be happy with that. Do you already have the magnetic track to match these sensors ?

Les.

[ChrisBParticipant @chrisb35596]

Why Les, is not 0.244um equivalent to 0.000244mm? Should be good enough for our applications right, or am I missing something?

I have not got anything yet, no track no sensors, just asking if it's something worth doing before I dive in.

[Bob DringParticipant @bobdring71940]

Good find!

Most commercial DROs are 5 µm and some are 1 µm. The number mentioned is about 4 times better at 0.244 µm.

I might mention that something similar, but cheaper, can be obtained as an IC part AS5311 from Digikey etc or as an evaluation PCB from the same sources. The manufacturer is Austria Micro Systems (AMS).

The chances are you might have to add differential line drivers and screened cable if you have the typical noisy ME environment.

Here in Australia you can also buy the 'Optimum' read head assembly for their DR05 display, at about US$75.(check the one with a mini din-6 plug as the DB9 connector one is much more expensive) They both have differential drivers. Optimum also sell the magnetic scale as a spare part too.

Personally I'm looking at the AS5311 IC plus drivers, as I want to make the read head as tiny as possible.

All this is theory on my part with no practical work as yet.

Bob

[ChrisBParticipant @chrisb35596]

I'm no expert in the subject, in fact I have no idea at all when it comes to electronics etc…I just happen to do lots of research on the internet trying to make head or tail of the thing in question

Someone seems to have used this read head with success, not much details tho…

**LINK**

Another thing which I'm not sure of is if the magnetic tape should be matched to the read head…say you're using a 1um read head, should the accuracy grade be the same?

[Les Jones 1Participant @lesjones1]

Hi Chris,
You are correct. for some reason I was thinking of 0.244 mm (Out by a factor of 1000) I have never used magnetic scales but I have seen the track advertised somewhere but I can't remember where, (It may have been Machine DRO)

Les.

[ZebethyalParticipant @zebethyal]

How long do the scales need to be if you are looking at 150 Euro each – you can get a 36" magnetic one for around £40.00.

I bought my igaging scales that work well with Yuriy's Toys TouchDRO from Taylor Toolworks in the US, 2 x 300mm and 1 x 150mm for £82.00 including shipping to the UK – I told him what I wanted and he set up a dedicated ebay listing for me.

Worth changing to shielded 'USB' cables at some point – my scales were resetting due to interference from the Mill motor – this made using them with the supplied displays a bit of a problem. All works perfectly now with a cheap Androd tablet running the TouchDRO app and some shielded cables to my interface board.

Edited By Zebethyal on 19/02/2018 09:54:18

[ChrisBParticipant @chrisb35596]

The igaging scales are not magnetic scales, those are capacitive scales – that's the reason for the price difference. A 1um magnetic read head on it's own from a UK supplier will set you back nearly £170.

I'm after magnetic readhead with cut to length magnetic tape such as the one linked in my first post. Contacted Yuriy yesterday evening and he confirms these **LINK** are compatible with his TouchDRO. I just need to figure out the resolution and frequency I have to choose…and the appropriate magnetic tape for them

[John HaineParticipant @johnhaine32865]

The A5311 looks very interesting, but I think one needs to look carefully at the data sheet to assess the possible accuracy including the device itself, its linearity errors, the scale, and temperature. Though the resolution is ~0.25 microns the read errors could be significantly larger. The basic price of the strip is quite low, EU7.50 for 300mm if you buy 1000, but cost in one-offs and for longer lengths could be somewhat higher. A good find thogh!

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