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Blog Housekeeping & Changes

It occurred to me the other day that I’ve been running this blog now for over 10 years! This is the second iteration, as the first was lost in a server crash shortly after it went live. (Wasn’t so good with backups back then!). In that time the traffic to the blog has grown exponentially, who’d have thought that people would actually like reading most of the waffle that comes out of my brain! ๐Ÿ˜‰

2020 Stats
2020 Stats

It seems the global Covid-19 Pandemic actually had an effect on my visitor numbers as well.

At the moment things are becoming a little cluttered on the back end, and there are a few errors that need sorting on the front end – thanks to some of my readers for pointing some of those out!

Site Theming

I’ve also been using the same theme for most of that time, but it’s beginning to show now with many updates over the years, and no updates to the theme code, that I’m going to start having some issues with the next versions of PHP, so this will have to change. This does join up with another project I have going, for a small webshop. The current theme unfortunately isn’t compatible with the most popular WordPress commerce plugins.

Broken Downloads

Thanks again to my readers for catching this one! It seems most of the downloads on the site have become broken, although I’m not sure why. I have changed over the Download plugin, and I am in the process of slowly moving over the shortcodes to the new system, so they will all be operational again.

On-Disk Size

Over the last decade or so of running, this blog has grown massively in size on disk – the usage currently stands at around 80GB. I really do need to reduce this footprint, so some time will have to be taken going through the backend filesystem to prune out any crap.

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Failed GU10 LED Lamp Teardown

GU10 LED Lamp
GU10 LED Lamp

Here’s a recently failed 5W GU10 lamp, which is completely dead – not even a single LED still shining.

Markings
Markings

According to the markings, this lamp draws 50mA at 230v & outputs 345 lumens

Lens Removed
Lens Removed

After popping the lens off the body, the failure mode is obvious. The top right LED has the Black Spot Of Death, where one of the LED dies has catastrophically failed in service. As these lamps usually have all the multi-die LEDs in series, a single failure will cause the lamp to totally fail. Running LEDs hard, with little cooling is a common cause of this kind of failure. There isn’t much in the way of heatsinking in this lamp, as the outer casing is plastic, and even though the LEDs are soldered to an aluminium cored PCB, the only other heatsink is the aluminium base for the PCB, which is in contact with the outer plastic.

PSU
PSU

Removing the LED board & backing plate allows access to the power supply in the rear of the lamp. There’s no switching supply in this one, just a large film capacitor.

Capacitive Dropper
Capacitive Dropper

Snipping the pins off the back allows the PCB to be removed, exposing the capacitive dropper from the mains. The output electrolytic cap has also failed on this board, as can be seen from the opened vent on the top.

PCB Reverse
PCB Reverse

There isn’t much on the back side of the board, apart from the bridge rectifier & a couple of resistors.

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R-134a Refrigerant Analyser Module Exploration

Main Board
Main Board

This unit recently appeared on eBay, as a spare part from a refrigerant charging machine, and I figured it would make a good explorational post. This unit analyses the purity of R-134a refrigerant gas, using an Infrared sensor cell, and communicates over RS-232.

The sensor cell itself is at the top right of the board, we’ll get to that later on. There’s a small diaphragm pump at the lower right, for purging the cell with air. The port with the red cap is the outlet, and the remaining open hose barb is the input of gas to be tested. This would connect to a flow regulator & solenoid valve that the board controls.

It’s pretty clear that this board has multiple applications from all the unpopulated components. There’s space for a keypad, indicator LEDs & an LCD on board, so maybe this can also be fitted to a handheld analyser?

Power Supply
Power Supply

From looking at the input circuitry, I can surmise that the input voltage is somewhere between 12-24v DC, as there is a 35v input electrolytic filter capacitor. There’s a couple of switching regulators which generate 5v & 3.3v rails for the board, with some input fusing.

Main Connector
Main Connector

There’s two serial links on this board, driven from the main microcontroller – the primary one is on the connector marked JMAIN, along with the power input & a couple of other unknown signals.

MSP430 Microcontroller
MSP430 Microcontroller

Over on the other side of the board is the brains of the operation – an MSP430 microcontroller, with an RS232 transceiver IC & another RS-232 port marked COM2. The remaining connector is a JTAG port for the micro.

Gas Analysis Cell
Gas Analysis Cell

Here’s the gas analyser cell itself, sandwiched under another board. There’s a temperature sensor on the side of the cell at the bottom, and even though there’s many pins on the header here, only a couple are actually used for the IR emitter.

IR Emitter
IR Emitter

Removing the screws from the top allows the board to be removed, which exposes the Mid-IR emitter component with an exposed element. This looks to be very fragile, so I won’t be messing with this much. From metering the connections, this appears to be driven at about 2v from the microcontroller.

Top Of Gas Cell
Top Of Gas Cell

The window into the gas cell looks to be made of something exotic – considering the IR application & the colour, this is probably Zinc Selenide.

Gas Test Cell
Gas Test Cell

Removing some more screws on the bottom exposes the bottom of the cell with another IR window, and an O-Ring where a pressure sensor sits.

Output Amplifiers
Output Amplifiers

There’s a couple of very accurate LT1884 Rail-To-Rail Precision Op-Amps next to the cell, most likely used to measure the output from the sensor itself.

Mid-IR Sensor & Pressure Sensor
Mid-IR Sensor & Pressure Sensor

Finally, there is a dual-window thermopile sensor, and a pressure sensor. I wasn’t able to get any information on either of these, but I did find some ranges of sensors for Mid-IR measurement operations, that mentions a wavelength around 10ยตm for R-134a spectroscopy.

I will try to get this module going & measuring some gases, if I can work out how to talk to it – I already know the serial lines so it’s just working out a command set. If anyone has any information on these, please do get in touch! A service manual for the refrigerant machine this came out of would be good!