Cheap chinese digital calipers and you

Some time ago I bought a bunch of cheap Chinese digital calipers and I was surprised to find that there is a port on almost all of them out the top. Now having looked up the format for both Starrett and Mitutoyo SPC formats, I have determined that it matches neither.

A cheap chinese vernierThis one happens to be a Mastercraft one but you can buy one off Ebay for like 8 bucks delivered. You can see the connector is already installed with solder onto the first three pins.

the pinout is as follows, from left to right looking at the face:

  1. Ground
  2. Data
  3. Clock
  4. +1.5v (or whatever the battery happens to be)

Here’s a bit of a closeup:

A look at the pinouts
A look at the pinouts, hastily soldered.

So I hooked it up to my oscilloscope and determined that there is both a data line and a clock. Here are the specs:

  • Data is sent in a packet of 6 nybbles.
  • Data is sent every 100ms
  • Data is LSB first
  • The numbers only seem to represent what’s on the screen. It represents units of the smallest graduation in the current display mode (inch/mm). For example, if values are converted to decimal: 1.5055″ = 3011 units or 3.45mm = 345 units
virgin saleae logic
A look at my virgin Saleae logic analyser

And yes, I bought a Saleae Logic Analyser. Unfortunately it does not support synchronous serial analysis. This would’ve been a great tool, had the software supported it.

Anyways, I tried to get the output to work on the logic analyser but the signal was really spotty. I determined it was because it only output 1.5v. I quickly whipped up a breadboarded circuit with a 7014D op-amp setup like a comparator to amplify the singal to 5V

the board to amplify signals
the board to amplify signals

Simple simple. This allowed me to run the signal onto my logic analyzer. It worked great except for the software not being able to decode the data. Wasn’t an issue though, I decoded it mentally.

Anyways, I hope this is useful to somebody. I can’t guarantee anything is correct but these device might make for interesting low-cost DRO units or something. There are some caveats however:

  • The cheap verniers are exactly that, cheap!
  • They don’t handle any kind of moisture, even a humid day is enough to screw them up.
  • The update rate is a paltry 10Hz
  • You can’t trigger the output when you want to, unlike SPC outputs of other manufacturers.
  • Battery life sucks
  • You can’t feed higher voltages to the battery compartment, no likey!

Again, hope this was helpful to somebody out there on the interwebs.

A look at a small solar panel set.

A while back I had found a bunch of little solar cells on Ebay for cheap. I hadn’t really looked at them or tested them in any real way but today I wanted to see if they could power even a small project. As it turns out, I would require a great number of them in order to make even an LED light up (Assuming no capacitor or storage device). Since the sun was going down, I needed a constant source of light so I used my desk lamp. Here are the comparisons.

Solar cell
The individual solar cell

Those are the units I bought. I think I got like 30 for $10 or something. relatively cheap, but not really. I was expecting some decent performance, which I got, but not nearly as much as I expected.

This is the competitor. It’s the old Archer 6-12V solar cell pack. It’s quite old (25 years), the lens is dirty but it still works quite well.

Archer Solar Panel
The old Archer solar panel

And here is the test cell/array that I soldered together.

Solar panels together
The solar cells soldered in a group of 4

Now, keep in mind that this was all done with a desk lamp. I maintained a certain distance from the bulb and only used the maximum measurement received by moving the panel around. Also given are comparitive measurements for the overall visible area exposed to light.

Old Archer Panel Cheapy EBay panel
Measured Voltage 5.245V .162V
Measured Amperage 305 uA 628 uA
Calculated Watts 1.6 mW .1 mW
Measured Area 14.05 1.6524
Cell Sizes .788in x .563in 1.063in x .433in
mW per .113mW per .06 mW per

That all being said,you could still run quite a few little things at that low current rating if you were to link together all of the cells for whatever reason. unfortunately, nothing that I want to do could use them. So the lesson for the day is “Quality over Quantity”

Also, as an aside, here’s my new Agilent U1271A multimeter. Works like a dream!!!

Agilent u1271A
My new Agilent u1271A, yay!

Perhaps tomorrow or someday I’ll give figures for sunlit voltages/amperages.

Happy 2011! uuh, I guess a bit late though.

It’s been well over two months since I last posted. Frankly, not a lot has happened in the meantime anyways. Work is going well and life is pretty good. That said, I’ve begun to regain my inspiration for electronics again and I’ve been going hog wild building stuff in the evenings. Just some stuff to touch on I guess…

My Lab

Well, again I have a secluded labratory in the shop I work at. It consists of 2 desks, two shelves and all of my equipment. It’s nice to hang around and listen to music and stuff while having access to all of the manufacturing facilities I could ask for!

Here’s a picture of my lab as I was setting it up.

The new lab as of 2011
The new lab as of 2011, this is an early picture. there is more equipment, parts and shelves now

It’s a real treat here and I’ve been sitting up here for many hours on my projects lately. Yay!

A veroboard planner PDF

Not really a project per say, however, somebody might want it. It’s for printed pcbs from PCBIran which have a ground loop on the outside and sets of rows and columns. Somebody may find it useful. I dunno.


The Shop

The shop I’m at is investing in new technology (IE. CNC mill and CNC Ram EDM) and I figured it’d be neat to take an overview picture. Sure is crowded though. 🙂 The mill, as was stated earlier, is a Haas VF-5 with a 40 taper and the Machine is a large CHMER EDM, more on that thing later in the post

Shop Growing
The shop I work at is growing, but not in floor space. 🙂

It’s actually much tidier now, this is when we were installing the EDM.

Rotary Table and CHMER EDM

I am developing a rotary table interface for the CHMER Ram EDM. The fools at CHMER decided that the machine requires NO extra M-codes for interfacing to external hardware… WHY!!!??!?

So now I have to monitor the outrush current of the pump, turn it on and off a prescribed number of times and then the rotary table can index. I’m still kind of in shock that nobody has ever presented CHMER with this problem. Weird!

The TI Launchpad

I have just ordered the TI launchpad for $4.60 or whatever it cost. TI is attempting to break into the hobbyist market something fierce. unfortunately, after looking at the development tools available, they are all way overpriced.

While they do provide a code-size limited version, which is useful for most things, I think people like to have unfettered access to their chips and what kind they use from a particular vendor. When the development tools that allow this are in the $500 range, that’s simply too much.

Perhaps there will be some good 3rd party support like Atmel and Microchip has and they can really take their MCU’s to the next level. It’d be very cool. 🙂

The Rest

Well, there is probably still more to say after such a long hiatus but I can’t think of it now. I do have some other ideas banging around in my head like a new design of the coolant refractometer which won’t foul. A robot that is machined beautifully and function on sonar. And a new coolant nozzle design that will kick Spider Cool’s ass from here to main street (I’m actually pretty stoked about this one).