Paint Flow Control Project, Chapter 3.26, Back to the Drawing Board

Happily, our Paint Flow Controllers worked fine in the installation at the painting facility in China. I'm actually not quite sure where the painting facility is but I think it's in Guangzhou in the south of China, fairly close to Hong Kong. It's where UEI (http://www.uei.com/) gets much of the painting done for their remote control units. Anyhow, because of the good results with our controllers, UEI and the Chinese facility are interested in purchasing up to a ten more controllers. Also Vivid Inc (http://www.vividinc.com/) would like two controllers for their own use at their Santa Clara facility.

We don't yet have the go-ahead on manufacturing the additional twelve or so controllers, but they are requesting some design changes, hence, Back to the Drawing Board. The design changes are not extensive, only requiring a change from the enclosure to an L-Shaped bracket since at the China facility, they mount the controller systems inside Hoffman boxes and consequently do not need the full enclosure, just an L bracket design. So I reworked the controller system design, again using Protocase (http://protocase.com/) design software with the aim of having Protocase build the L brackets for us since Protocase has built high quality enclosures for our previous control systems.

Here is my latest L bracket design:

The bracket has cutouts for the 4DSystems 4DCAPE-70T (4DCAPE_70T/) and for the AW Gearmeter (http://aw-lake.com/) MX9000 flow meter display unit, plus the AC ON/OFF switch and the Reset pushbutton. Both these devices have worked well. The Beaglebone Black microcomputer (BBB) plugs onto the 4DCAPE-70T and allows us to make a good Graphical User Interface (GUI) for the users to set the paint flow setpoint and operate the control system software installed in the BBB. Recall that I chose to use the BBB because of its many features including analog and digital I/O and its 1 GHz speed. I programmed the BBB in Python (Python), using tkinter (tkinter) and matplotlib (Matplotlib) to make the GUI.

Thomas Nguyen of Vivid Inc and I had concerns about use of a positive displacement flow meter such as the AW Gearmeter because those flow meters can be plugged up by paint contaminants. Sure enough, there were problems in the Chinese painting facility, resulting mainly from paint getting coagulated because of bends and obstructions in the tubing. Thomas got the tubing straightened out and had filters installed in the tubing to ensure that the paint would be clean and flow freely through the tubing to the paint guns. A further advantage is that the reject rate has greatly been reduced with the cleaner paint. Anyhow, we have been happy with the AW positive displacement gear meters and will continue to use them in the future systems.

Along with the change to the L-Bracket, I decided to change the power supplies to a different package also from Meanwell (Meanwell RS-15), the RS-15 family because of the connections to a barrier strip on the RS units. The Meanwell supplies have worked just fine, allowing a very wide range of AC input power, necessary for the installations in China.

And I am having to correct some design goofs in my Analog interface board. I had the Collector and Emitters of the output transistors turned around, and also I didn't provide enough space for the Phoenix connectors, minor but necessary fixes. The Analog I/O board utilizes outputs from the BBB Pulse-Width-Modulation (PWM) circuitry to provide 0-20 mA current outputs to control the paint pump and a simple interface (a resistor) to the BBB;s Analog-To-Digital-Converter circuitry to measure the current output from the AW Gearmeter display unit. Here's the resulting board layout from Kicad (Kicad):

Analog I/O Board for Paint Flow Control Systems.

As I said, we don't yet have the go-ahead to manufacture more paint flow controllers but hopefully soon.