[How do I?] Lengthen or Disable timeout feature of cheap DRO's

[PLASTICULTURE]

I have been using these cheap DRO's on my Mini Mill, for quite a while. The reliability has been pretty good. Especially after shielding the wires to electrical interference. I have searched a number of places YouTube, Google and even got in touch with the manufacturer. I have yet to find a solution.
After being a member of this forum for only a few months I have decided to ask my first question.
I have wanted to replace the batteries with a power supply. That I can do with no issues.
However the timeout feature that is inherent to these DRO's is really frustrating.
I would like to know if defeating or lengthening the timeout feature is a possibility with these units and how it's done.
Working faster is not a good option.

 

[itsme_Bernie]

If you turn off/on the power to the DRO before it times out, does the unit turn back on automatically, or stay off?

 

[itsme_Bernie]

You may need to open one and post a pic here for us to see what is happening inside. The timing may be set in the microcontroller (maybe).
There is a "hack" to have another timed relay turn the power OFF and ON, or just ON on a regular basis before the microcontroller shuts off, but unless your DRO scales are absolute, and the program shows absolute no matter what, it might mess up a reading if it shuts off during a cut.

 

[RJSakowski]

The scales with auto off that I have worked with only shut off after a period of inactivity. It shouldn't shut off while making a cut.

 

[pavyan]

As @RJSakowski writes, it works like this: when the reader remains motionless for more than a programmed time (5-8 minutes, I don't remember), the display turns off automatically (but ONLY the display - the measuring system works continuously).

If you make a move (move the reader) before this time has passed, it waits again - and turns off again after a programmed time (but: making another move with the slider will extend the display's active time again).

I have the same old SHAHE quasi-DRO, it's about 10 years old - but this auto-off function suited me very well because I didn't have to remember to turn it off when I left the workshop. Now I moved it to the milling machine's quill because I use it relatively rarely - and half a year ago I bought three newer 5403-xxxF scales for the built TouchDRO.

@PLASTICULTURE: By the way, I can tell you that the newly purchased ones do not turn off automatically - so there is a way out: namely, buy the SHAHE 5403-xxxF type?
Mine has a yellow ON/OFF button, white function buttons and a dark blue cover of the aluminum scale and display - as in the attached photo:


At the moment it does not matter to me whether these auto-off features exist or not because scales are connected to TouchDRO.
Warning: as we know, the Chinese always attack without warning - so the specification can change suddenly, and today the 5403-xxxF type can have an auto-off function.
And it is known that if you ask a Chinese about anything, he will always answer the same: Yes, yes, my friend!

@itsme_Bernie: This is a photo of the inside of the "old" SHAHE slider - mine, but I believe the PLASTICULTURE one is identical; there is an added 0.1uF ceramic capacitor to block interference (green):

 

[PLASTICULTURE]

If you turn off/on the power to the DRO before it times out, does the unit turn back on automatically, or stay off?

Yes, when the DRO times-out... if I press the ON/OFF button the DRO will power back up and yes it retains the dimension.

 

[PLASTICULTURE]

The scales with auto off that I have worked with only shut off after a period of inactivity. It shouldn't shut off while making a cut.

You are correct! However each readout is independent and if that axis is not in motion it will shut off (timeout). Thus, I could be taking a cut only on the "X" axis and both the "Y" & "Z" will time out. That is what is frustrating.

 

[pavyan]

If you are so desperate...
Because the processor is hidden, encased in resin on a PCB and we have no data, no schematic or soft of the SHAHE DRO, there is another way out, but it is quite laborious and it is an unexplored path, a small minefield to be recognized by battle
I suppose that it is possible to design and make a simple timer based on a 555 timer that will periodically, in a time one minute shorter than the auto-off of the SHAHE display, turn the power off and on immediately (0,5-1s). The controlling element (a bipolar transistor or rather a small MOSfet) would be connected in parallel to the ON/OFF microswitch, which is built into the display.



Post Scriptum:
It was late and I made a mistake in my haste - sorry
Unfortunately, it's not that simple: the circuit should generate two short pulses in a short time interval - the first pulse "OFF" and the second pulse "ON". And this cannot be done in a simple way, with a single 555 chip; there must be at least two 555 or other IC's.
It would have to be a slightly more complicated generating circuit.
Apart from that (the second mistake), the waveform should be reversed, but that's less important - I just wanted to illustrate the principle of operation.

 

[itsme_Bernie]

You may need to open one and post a pic here for us to see what is happening inside. The timing may be set in the microcontroller (maybe).
There is a "hack" to have another timed relay turn the power OFF and ON, or just ON on a regular basis before the microcontroller shuts off, but unless your DRO scales are absolute, and the program shows absolute no matter what, it might mess up a reading if it shuts off during a cut.

Yeah, I had a space-cadet moment suggesting it could shut off during a cut, hah hah.

I think Pavyan posted a schematic for what I was attempting to describe. I thought of one more possible function, which may be less useful than Pavyan's schematic which shuts off and on so quickly you wouldn't notice anyway.. BUT.. If there was a circuit to check if the DRO had moved since the last time the added timer circuit did it's thing, you could avoid many of the shut on/off cycles.
So logic would change to a timer that would start every time the new sensor/circuit stopped detecting DRO movement since last Auto shutoff/on (added with your new circuit), When the DRO did not detect movement, the new timer circuit would start again. Now if the screen would flicker or anything when shutting off and on, that would happen less often, even though it probably wouldn't really matter very much.

Just a thought.

 

[pavyan]

I will add a post - because when @PLASTICULTURE posed the problem and I came up with the idea that an electronic circuit in the form of a "double pulse generator" could solve it - I started looking online for just such a SIMPLE generator.
I was surprised, because my several hours of searching did not yield too many results, or to be honest - only a few.
I noted these results, so I will post a few links I found.
Of course, these are not ready solutions, but only inspirations, circuits that can probably be used to design and build a ready circuit that would fulfill the task set.
However, this requires a lot of time - i.e. design and testing, and since no one has probably done this before, it is an "unknown land".
In addition, it is not known whether it will work at all according to our expectations.
Personally, I don't have time to look into this - but since I found some information, maybe it will be useful.
PS: By the way, turning off this DRO with the ON/OFF button does not cause loss of position; only the display is turned off - the measuring system works continuously until the two parallel CR2032 batteries run out (a year or two).

1. https://www.learningelectronics.net/circuits/pulse-generator.html
2. http://www.seekic.com/circuit_diagram/Basic_Circuit/Double_pulse_generator_HEF4538_circuit.html ( I couldn't find PXO301-858 chip used here - maybe it's some chinese "invention"? ).
3. https://www.analog.com/en/resources/design-notes/multiplepulse-generator-aids-ic-testing.html
4. https://schematicsforfree.com/files...ators/High Frequency Dual Pulse Generator.pdf
5. CD4060, maybe it would be useful?:
https://www.eleccircuit.com/4060-timer-circuit-project/ and https://dmohankumar.wordpress.com/2012/05/13/design-your-circuit-part-ii-cd-4060-timer/ and https://www.homemade-circuits.com/how-to-understand-ic-4060-pin-outs/