Sunday, June 14, 2015

What's Inside? Honeywell 3 Axis Compass HMC5883L

One of the more remarkable bits of the last 20 years is how previously very complex and expensive technology has been shrunk in size and cost.

The Honeywell HMC5883L 3 axis compass is a good example.

These sensors probably find high volume applications in cell phones.

It's still a marvel to me how one could fabricate three small bits of silicon (including 2 which are undoubtedly MEMS), package them into a single substrate and then assemble it into an Arduino friendly board for a of 99 cents!

Thursday, June 4, 2015

Poor Man's Metallurgical Microscope

In retrospect I should have bought a metallurgical microscope for the type of work I do..... this video explains how I work around the limitation of a biological microscope to added top side illumination.

A fun outing with fabricating some moderately precise components on a metal lathe.

Saturday, May 30, 2015

AIMOmeter MS8217 Multimeter: Fluke 17B clone with lots of problems....

In the sincerest form a flattery some vendor has copied the exact case of a meter from the much better known Fluke corporation.

Sadly, they did not copy the quality inside such a meter.  Some clear design errors in the meter.

While I did not expect much for $29.99, I was surprised that I was able to buy the meter on  If this was an ebay or alibaba purchase I would have been not as surprised.... I don't know why.  I guess I need to be vigilant no matter what the vendor.....

Some clear design errors which is just so surprising when they could be easily avoided.

Monday, May 18, 2015

Filament LED Long Term Test

There has been much speculation on the service life of these filament LEDs.  Sounds like a good topic to study so I bought one and have been running it 24/7 while mapping out the light output.

At the ~600 hour mark (1 month) I am now getting a sense of the life time of the bulb.

Tuesday, May 12, 2015

BMP180 Barometric Pressure Sensor Extereme Teardown

A much more challenging tear down.  The BMP180 is a pressure+temperature sensor all in a neat little package with a digital interface.  As seems to be the case these days support is excellent for the Arduino platform with a robust library ready for use.

The package looks like a metal - can oscillator... with one big difference: a hole on top!

The top looks like it's simply soldered to the substrate... but no matter how heat I applied it stayed stuck.  An area worthy of further study.

However, as always, acid de-encapsulation worked here and two pieces of silicon were extracted.  One is a pressure sensor, the other a micro controller with I presume a temp sensor.

The die size is at the limit of my microscope.... might be time to get a metallurgical one...

Wednesday, April 29, 2015

What's Inside: Temperature and Humidity Sensor

A part of  a "big buy"... well, OK, $20.00 worth of parts from ebay.

So many just excellent sensors are now available for such tiny amount of money.

This sensor is a really good example... it measures two parameters and presents the data on a serial one-wire interface. All of the complex sensor characterization and trimming is neatly stored inside a micro-controller that's wire-bonded to the back of a small circuit board.   30 years ago this controller would have probably made a pretty good CPU section for a home computer... now it just disappears into sensor assembly.

What was once remarkable on it's own now just becomes a bit actor in the wider technical field... makes one appreciate just how many small CPUs are now part of every day things...

Philips "Basic Bulb" LED: End of the Race to the Bottom

Probably about as cheap as a bulb as possible without sacrificing the non-negotiable (UL/CSA safety), light quality.

By not achieving a high power factor and not enabling dimming the designers were able to jettison tons of cost.  Sometimes these savings are really subtle, for example, when dimming a bulb it often hums due to magneto-restriction in the transformer cores. This is often overcome by adding potting compound to dampen and silence the bulb which drives cost.

Light pattern surprisingly good, efficacy very good.  One can see a place for such a light bulb in the market.