TouchDRO is designed to work with a wide range of scales and machines, but it will not work right out of the box. After the application is installed, it needs to configured to match your particular setup. The process isn’t complicated and takes just a few minutes, though.
By default the application is configured for a three-axis vertical milling machine that uses imperial units. If that matches your setup, the only thing you’ll need to do is to configure your scales and the DRO will be good to go. Otherwise, there are a few additional settings that needs to be changed.
Application settings are set using the “DRO Settings” page that can be reached via the “Settings” option on the context menu. Depending on the device you are using, the context menu is accessed either via a dedicated menu button, or via the “three vertical dots” (AKA “Action Overflow”) in the top right corner of the screen.
|Designated menu button can be seen in the lower-right corner of the phone|
|Pressing the "three dots" in the upper-right corner brings up the menu|
Settings page is split into several setting groups, such as “General Settings”, “Connection Settings”, and several axis-specific groups. In this post I won’t go into explaining what each setting does. Instead I will cover the settings that needs to be set for the DRO to become usable. For the complete explanation of each setting please refer to the TouchDRO Settings Overview.
If you intend to use the DRO with a lathe, rather than a milling machine, the “Machine Type” setting needs to be changed to “Lathe”. This setting determines what functions are available, how the axis details screen looks and how the points and tools appear in the list.
This section determines how the application will communicate with the scale interface controller. By default TouchDRO is set to use BlueTooth, but if your tablet doesn’t have a built-in BlueTooth controller, the app supports USB connectivity with some devices.
Please note, USB works with a limited number of controllers. Namely, the flavors of Arduino board that use a separate ATMega for USB communications, such as Uno and Mega, or the ones that use FTDI 232R serial-to-usb chip, such as Duemilanove and Namo. The FTDI chip is commonly available mounted on an easy-to-use breakout board, which can be used in place of the BlueTooth transceiver with a MSP430 Launchpad.
No configuration is needed for the BlueTooth mode, but in USB mode the BAUD rate in the app needs to match the BAUD rate used by the interface controller. If the transfer rates don’t match, the app will not be able to receive any data.
X, Y, Z, and W axis Settings
The axis settings are very similar for the four linear axes, but some axes have additional flags that need to be set. Namely, with the exception of the X axis, each linear axis can be shown or hidden using the “Enable Axis” setting. The behavior of the W axis can be further changed using the “Axis Target” setting. Based on the selected value the readout can be either shown or summed up with one of the other three axes. In the latter case, please make sure that the target axis is enabled as well.
Once the desired axes are enabled, the application needs to know what is the resolution of the scales used for each axis (in “counts per inch”, or CPI). The values can be set for each axis individually using the Axis CPI settings.
Counts-per-inch for some common scales are as follows:
These values should get you started, but for the best accuracy I recommend that you calibrate your scales once they are mounted. This will account for any cosine error you might’ve introduced into the setup, etc.
Finally, if the readout from the scales is “backwards”, i.e. the number decrease when they are supposed to grow, etc. the readout can be inverted by checking the “Invert Readout” option.
Please note, that the CPI and direction for the axes that are summed together don’t need to be the same. For instance, you can use glass scales on the kneed and a standard “caliper” on the quilld. The app will figure out the proper conversion ratio internally to get the scales in sync.
The tachometer is very similar to the other axes, except it uses Counts Per Revolution instead of the Counts Per Inch. The value is set to 1 by default and can be changed using the “Tachometer PPR” setting. Similarly, if the value appears to be negative when it should be positive and vice verse, check the “Invert Output” option.
This post covered only the bare minimum setup needed to get the TouchDRO application to display the correct position. There is a plethora of other settings that will enable you to customize the application to your particular needs. For the complete explanation of each of the application settings please refer to the … page. Finally, to make sure that the scales’ CPI is set as accurately as possible, I suggest that you calibrate them on the machine using either the process I described in the “Calibrating DRO Scales” posting or something similar.