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All Gauges Attached to DRO
The remaining gauges have been attached to the DRO. There's now 3 gauges on the lathe and three on the mill. All of the gauge channels are now populated and attached:
Each card has a PIC on it that converts from the gauge serial protocol to I2C. The main ARM processor then interrogates each of the relevant gauge channels over I2C and displays the values.
Each of the gauge channel PCBs is identical, the firmware is almost identical, the only difference is the I2C slave address, which is 0x30 and 0x40 for each pair of PCBs on the same I2C bus. There's three I2C busses.
The main DRO PCB has an ARM processor on a commercial LPExpresso card:
The TFT screen is a touch screen and there's a menu system running on it. The DRO can be set to display the lathe channels or the mill channels. The smaller OLED displays then show the appropriate axis tags. When running in lathe mode the two X axis values can be added together.
The gauges have been attached with 3D printed plastic mounts. I may re-make them in metal if they aren't rigid enough.
The gauges are held in clips that can have screws clamping them from the sides:
I've removed the buttons from the gauges if they were pressed by the clips. The buttons aren't needed and you also don't need to read the displays as the DRO does that.
The batteries aren't needed either as the DRO channels all have a 1V5 power supply. The gauges run from that and are powered all the time the DRO is powered. The power down of the gauge display doesn't stop the serial data stream, either, which is nice.
The mill X gauge is mounted in a similar way:
The Y as well:
And the Z gauge:
The lathe bed gauge was one of the more complicated mounting arrangements.
I've started to use the DRO and it certainly makes measuring things much easier. I need to check that the gauges are working correctly by comparing with a dial indicator.
7 comments:
What sort of read rate do you get. Usually there's a limit to how fast you slide those things?
I get several readings a second on each axis. All six channel daughter boards are read all the time, I only display three axes at a time as I only have 3 seven segment displays. I'll post a video of the DRo in action. The gauges themselves seem to have no upper limit to how fast you slide them, they know absolute position. They can easily keep up with the mill or lathe movement.
All the image links are gone :(
Yes, I've had an image problem with the blog. I still have the images, I just need to re-upload them, sorry.
Images added
I was looking to do something similar for a 3d printer and came across your blog. The circuit board of my caliper gauge looks exactly like what you have in the pictures. Could you please share the 3d model for the plastic mount that holds the circuit?
Yes, I've added two models (Openscad) to the github repository:
https://github.com/blackjetrock/arm-dro
Hope that helps.
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