DIY Digital Caliper

[MitkoDyakov]

I've done some playing with this kind of stuff over the years- I developed the DRO system for Sherline after looking at a bunch of low cost solutions.  Here are a couple of inputs that I haven't seen in the discussion so far.

Book- "Capacitive Sensors" by Baxter, IEEE press.  Only text I've seen that covers these in detail.  A small part of the book- engineering library?

There was a project in "Home Shop Machinist"- Village Press many years ago on this topic.  The guy ended up CNC engraving the spars himself.  He couldn't get 1 meter length and the PCB accuracy wasn't great.  The builder made the spars but used off the shelf readout heads that he could buy cheap that had something like SPI outputs.  I've never seen the asics in these things for sale anywhere.  I googled this article and it didn't pop right up- try Village Press.

Good luck.

Oh this is gold, thank you so much.

[MitkoDyakov]

This analog stuff is a gift that keeps on giving. Now I have a new issue.

My amplified signal rides on a crispy 50hz signal




From what I read this could be remedied with Notch Filter. To implement this filter I need split power supply.

Are there any options to do this with solution with single power supply?

p.s. I am not complaing this is actually fascinating!

[ali_asadzadeh]

My gift to your project
Connect the PWM signal with 50% duty cycle to STM32 the PWM frequency in my case is 64KHz,
Please share the project kicad files along MCU code.

[MitkoDyakov]

My gift to your project
Connect the PWM signal with 50% duty cycle to STM32 the PWM frequency in my case is 64KHz,
Please share the project kicad files along MCU code.

Updates, you can find on the hackaday page. What is this circuit called?

[amyk]

It will be hard to beat the cost of the cheap ones, but maybe you can decap one and see if they're using an MCU (4-bit? 8-bit?) or an ASIC.

There is some more information about the type of capacitive sensor they use here: https://www.mdpi.com/2076-3417/8/12/2419/pdf?version=1543401417

[MitkoDyakov]

It will be hard to beat the cost of the cheap ones, but maybe you can decap one and see if they're using an MCU (4-bit? 8-bit?) or an ASIC.

There is some more information about the type of capacitive sensor they use here: https://www.mdpi.com/2076-3417/8/12/2419/pdf?version=1543401417

I have no delusions that I can make it cheaper. Cost is not the only factor. There is no module you can get to play around with regardless of price.

On the decapping part there is this guy



I had made progress after adding a simple notch filter. Also a hardware redesign could also improve the noise level.

https://photos.app.goo.gl/LLSTbh9mK8QkKRbe8