New DRO for my Sieg X3 Mill Finished

In the last post I started covering the installation of the glass scales on my Grizzly G0463 (AKA Sieg X3) mill. You might recall that I got the scales loosely mounted on the mill but didn’t have a controller to use them with. I didn’t want to tie-up the unit I’ve been using for testing, so before going any further I had to build a new one. This weekend I got some free time to finally build the controller and [mostly] button thing up.

Adding DRO to my Grizzly G0463 (Sieg X3 Mill)

Several people asked me to post pictures of my DRO setup. Today I started installing a new DRO unit on my Grizzly G0463 (A.K.A. Grizzly Small Mill/Drill or Sieg X3) mill and decided to take advantage of this opportunity to take some pictures and post the progress.

I’ve been itching to get a set of glass DRO scales for a while but the cost has kept me off. Last July I randomly emailed a seller on eBay and asked if they would happen to have a returned or blemished unit they’d sell to me for experimenting. Surprisingly the guy replied that he is discontinuing the Easson scales and has two units [8” and 16”] that he’d sell at a steep discount. Additionally, he had one with a broken reading head that he’d throw in if I wanted it for parts. He wanted $200 for all three of the scales, including shipping. Needless to say, I jumped at the opportunity. When the scales came, I took the broken unit apart to see what’s inside and right off the bat found the problem. The Vcc line was broken and the exposed wire was shorting to the case. Five minutes later I had three working scales: one 8” long, and two 16”.

 

Selecting Scales for a DRO

When building a DRO the selection of scales is the most critical decision. Touch DRO Android application can work with a number of different scale types, ranging from inexpensive calipers to 1 micron glass scales. In addition to the cost considerations there are technical parameters that you should take into account. In the previous post I explained which parameters really matter in a DRO setup. Now let’s take a look at some of the commonly available scales and see how they stack up.

Selecting Scales for a DRO - Six Parameters that Matter

Things were easy when iGaging "Remote DRO" were the only scales Android DRO supported. Now that it can work with most of the common scales things are becoming a bit more confusing, judging from the number of emails I've been getting lately. With other things being equal, the choice of scales will have the biggest impact on you DRO's performance. There is a number of options, ranging from cheap Chinese calipers to glass scales and other quadrature encoders. Although I can't definitively answer the question "which scales should I use for my DRO setup", in this post I'll try to explain which parameters matter most in a DRO application.

Android DRO Mini FAQ #2

As the interest in the Android DRO project grows, so does the number of questions I get each day. Some of those questions keep coming up regularly, and since it’s been almost a year since I posted the “Android Digital Readout Micro FAQ”, it’s time to post another one. This post will not cover every question you might have, but hopefully it will address most of the common ones.

Mixed Scale Controller Firmware Posted

Recently I've been working on a new version of a DRO controller that will be able to read a combination of different scales. Although the project is taking much more time than I anticipated, I’m making steady [but slow] progress. Last week I had some free time, so I was finally able to button-up some stability issues with the common “Chinese” scales. Unfortunately I still haven’t finished a truly universal version, so you won’t be able to mix glass and capacitive linear scales (yet). Never the less I posted two versions of the firmware: one that read up to four scales and one that reads the common capacitive linear scales. Links to both versions are posted on the DRO Project Downloads Page.

Finishing the Voltage Shifter for Mixed Scale DRO

A few weeks ago I posted the build instructions for an adapter board that can be used for interfacing various digital scales to the MSP430 Launchpad DRO controller. Following those instructions you will end up with a base adapter board that still needs to be configured for your particular setup. This includes providing each scale with an appropriate power supply voltage, hooking them up to the corresponding “virtual ground”, and connecting the adapter to the MSP430 Launchpad. In this post I will use the DRO unit I built for my own mill as an example of a mixed-scale setup.

Build Instructions for Voltage Shifter Circuit

Last post covered the design considerations for the Voltage Shifter required for the Mixed Scale DRO Controller. As promised, in this post I will provide detailed build instructions for this circuit. The board is designed to work with up to four scales and has three power rails. One provide 3.3V power supply to the comparators and [potentially] iGaging scales; the other two can be set to any voltage between 1V and about 18V. Although the firmware doesn’t [yet] support glass scales or tachometer input, this board is ready for them.

3"x4" 1200 hole stripboard
with a track cutting tool

Voltage Shifter Circuit for Mixed Scale DRO Controller

In the last post I introduced the new version of DRO controller that is able to read a mix of common digital scales. You might recall that “Mixed Scale” controller uses the same MSP430 Launchpad development kit as the “Basic” version, but requires a bit of extra hardware. Unlike the the iGaging scales, which work quite comfortably with the 3.3 Volt power supply, most other inexpensive capacitive scales use 1.5V (nominal) power supply. This means that their outputs can’t be reliably read by the MSP430 microcontroller. Similarly, glass scales and quadrature encoders use 5V power supply. MSP430’s inputs can tolerate up to 3.6V, so connecting the glass scales directly to the Launchpad will permanently damage the inputs.

Mixed Scale DRO Controller Project Update

Mixed Scale DRO Controller with MSP430 Launchap

So far the DRO controllers I’ve designed have been able to read only the IGaging (Shahe) Remote DRO scales. Lately I’ve been getting an increasing number of requests for a firmware that could read the standard “chinese” linear scales.A few months ago I started working on a new version that would do just that. Although the project is still a bit rough around the edges, I’m pretty sure that the hardware will stay unchanged and any future updates will be done via firmware. Rather than holding off until the whole shebang is done, I decided to post the stable version of the firmware. In the next few posts I will provide details for the project, design considerations, build instructions and firmware implementation.