Chinese Scales

[Sub MandrelParticipant @submandrel]

[Sub MandrelParticipant @submandrel]

I have fitted the ‘cheap’ (not THAT cheap!) DROs to my mill, and made a separate readout box with big 3/4″ LED digits and a tachometer as well.

 

I have a strange problem. For each readout I have a switch that can short one or the other data line. This allows access to features you can’t access with the zero and off buttons.

 

One switch zeros the display , the other switch puts it into a fast readout mode, which is much better.

 

But this only works with two of the DROs. The big one on the X-axis different. For example you need to press both switches in turn to get fast mode, or to stop it. you can only zero it in ‘slow’ mode. Sometimes it goes into what appears to be a ‘hold’ or even a ‘relative’ mode.

 

But.. I can’t work out the logic of all this and it isn’t in the instructions. Has anyone worked out what the secret is?

 

Neil

 

[blowlampParticipant @blowlamp]

Not being an electronics kind of person, I don’t know if this link will help, but I remember reading about it when I built my Shumatech DRO.

http://www.shumatech.com/support/chinese_scales.htm#Hold and Fast Reading

 

 

 

Martin.

Edited By blowlamp on 30/09/2011 22:06:53

[Les Jones 1Participant @lesjones1]

Hi Neil,

Here is a link to a state diagram which shows how to move between the various modes.

Chinese scale states

 

It is possible that some scales do not conform to this diagram. I have not seen any scales that can be zeroed when in fast mode. If you want to do that on your remote display you need to have a zero button which captures the current absolute value from the scales and then display the difference between that value and the value being output from the scales.

This is how the Shumatech DRO350 (And DRO550) work. I wonder which micro you use ?

I have played around using the PIC16 and PI18 range to read these scales.

 

Les.

[Sub MandrelParticipant @submandrel]

Hi Les,

 

Ooops – I posted this as a comment to your reply to HH by mistake.

 

That diagram is exactly what I was looking for. It makes sense now, although it doesn’t mention that pulling CLK high in normal mode zeros the scales.

 

I have been entering ‘max hold’ mode without understanding what it was, and thinking I had lost synch with the unit or something!

 

I tried re-reading the leaflet that came with the scales; a masterpice of mis-translated mis-direction!

 

The two other scales simply toggle in and out of fast mode, and yes you can’t zero in fast mode (the one thing the leaflet does explain properly).

 

I use the Atmel AVR micros, for the display and tacho a TINY2313, but I’ve used a fair few different ones now. Next to me is a lttle Arrex Yeti robot – with a MEGA8 in it, I bought it partly as a way of learning ‘c’, as I normally use assembler.

 

Yeti page on Arrex website

 

Thanks to Steve too. The connectors mentioned were available from Arc Euro, they are just copper springs on a plastic block and don’t work very well. I soldered my cables in place and filled the holes with hot melt.

 

One thing I did, which I haven’t seen anyone else do, is fit the X-axis readout behind the table under some thin 1″x1″ aluminium angle. It seems to stay swarf free and it keeps cables out of the way and I can still add stops on the front of the table.

 

Neil

[An OtherParticipant @another21905]

Don't know if this is the right place for this: I've been playing about making some modifications to some of these chinese scales, and came across something which may be of interest –

I have seen posts from people complaining that the battery life sometimes seems very short – on the 4 scales I am working on, the on/off button does not switch off the measurement electronics, only the display. This suggests that if you are going to leave these things unused for long periods, it might be a good idea to remove the battery.

The scales I am using are from 3 different suppliers, and do look different. Also the 'internals' are not the same, but all have the same power issue.

[JasonBModerator @jasonb]

Common on most of the digital measuring equipment, the battery keeps it ticking over to remember where it was zeroed and the "off" is only for the display

[Neil WyattModerator @neilwyatt]

The 'off' current is also very different with different scales!

Neil

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