Electrical – Page 5 – owenduffy.net

Review of Hantek DSO8102E hand held oscilloscope

This article is a brief review of some issues that were found with initial testing of a Hantek DSO8102E two channel 100MHz hand held oscilloscope.

The DSO8102E is a member of the DSO8000 series (DSO8060, DSO8070E, DSO8100E, DSO8150E, DSO8200E), and shares most specifications across the series.

The specifications are very impressive, and price at just under $1000 for a Chinese brand seemed reasonable (hand held oscilloscopes are expensive compared to bench oscilloscopes).

The test scenario was a practical application, observation of the data traffic to/from a DHT22 temperature and humidity sensor in the project ESP8266 IoT DHT22 temperature and humidity – evolution 2. Continue reading Review of Hantek DSO8102E hand held oscilloscope

Last update: 18th October, 2018, 8:07 AM

The fraud of energy efficient lighting – LED lighting

Having been pushed into CFLs due to conservationist action that removed incandescent lamps from the shelves before mature reliable product was available, I ventured into LED lighting because of the failure rate of the CFLs.

The LEDs are about the same power consumption as the CFLs they replace, the hope was that they had a longer life (you have seen the claims of 100,000 hours).

Two years after cutover, it is time to review their performance.

Of some 25 11W LEDs installed, most would not be used for an hour a month, but 11 are used every day for an average of around 4 hours per day.

The pic above shows the failures of two years operation, 5 of 11 have failed. The average life of the lamps that failed is less than 3000 hours. probably in the region of 2000 hours, certainly a long way short of the claims of 50,000 to 100,000 hours. Continue reading The fraud of energy efficient lighting – LED lighting

Last update: 23rd April, 2017, 3:54 PM

Modifications for Jasic 200A TIG welder and pedal

In about 2009 I purchased a Uni-mig Jasic 200A TIG welder (though these are sold under many brands).

The welder came with unusual 2 and 5 pin connectors for the torch trigger switch and an optional pedal. The optional pedal was quoted at around $500, probably partly as the seller had locked the market up with the unusual connectors. (I note that the XS12K2P etc connectors are now available on Aliexpress.)

There is no standardisation of these connectors, but the pedal internals are pretty common. A quite common configuration is a 2 pin Foster (microphone) connector for the trigger switch and 3 pin Foster (microphone) connector for the current pot.

A further usability issue is that the pedal varies current from 5 to 200A, it is not possible to set the maximum current when the pedal is fully depressed. Continue reading Modifications for Jasic 200A TIG welder and pedal

Last update: 22nd February, 2017, 8:59 PM

Earth electrodes in parallel

I came across an article giving guidance to hams about antenna / station grounding, presumably for lightning protection.

The question is, what is the ground resistance improvement of one electrode over the two shown above. Let’s ignore the issue of earthing conductor size and deal only with the issue of parallel electrodes.

We don’t know the soil type, and we need to guess the spacing… it appears to be one house brick which is 9″ or 225mm in a lot of the world, perhaps that applies to the pic.

By way of an example, let’s make some assumptions that are likely to apply in lots of practical implementations. Continue reading Earth electrodes in parallel

Last update: 23rd January, 2017, 9:17 PM

AU ordinary power plug, plug packs and extension cord sockets

Electrical items personally imported to Australia (eg eBay purchases) commonly do not comply with some basic mandated safety features that can be checked with a cursory visual examination.

10A Extension cord sets (AS/NZS 3120)

Extension cord sets sold in Australia for more than a decade must have two ‘new’ features as in the pic above:

insulated live pins (active and neutral); and
shrouded socket;

Plug tops at less than 20A (AS/NZS 3112:2011)

Plug tops at less than 20A must have insulated live pins (active and neutral), and the earth pin if fitted should be longer to make contact first. Continue reading AU ordinary power plug, plug packs and extension cord sockets

Last update: 25th December, 2016, 8:17 AM

LED lighting woes

Pressed to replace working lighting with so-called ‘energy efficient’ lighting by well-meaning but narrow sighted conservationists, I recently replace about 25 CFL lamps with 12W LED MR16 lamps.

They have started failing now after a couple of years of service, perhaps a few thousand hours of service. So much for the claims of 100,000 hours… clearly preposterous.

In an effort to identify which of the switched mode power supply or LED assembly was the problem, I tried to substitute LEDs to different power supplied.

That was not a good idea, lets look at the anatomy of your typical Chinese junk MR16 LED.

Above is the complete 12W MR16 lamp with GU5.3 bipin connector on the back. Continue reading LED lighting woes

Last update: 25th April, 2017, 7:36 AM

Backup for NBN VDSL access

The change from Telstra ADSL to NBN VDSL drops the POTS line that gave telephone access independent of premises power.

Telephony is now provided by an ATA integrated into the VDSL modem, and dependent on mains power.

NBN makes no definitive statements about battery backup to the node, or endurance of any battery backup. Nevertheless it appears from pics people have taken of the node cabinets that the bottom layer is batteries and it is likely that they have endurance of more than 10 hours.

Above, a pic of an NBN FTTN cabinet from NBN’s website, and showing batteries in the bottom layer.

NBN is not customer facing, and it seems they will provide are reluctant to provide all manner of information useful to end users, perhaps guided by lawyers who do not want to create any obligation or liability for the company… the way of modern telecommunications.

In that context, it would seem worth the risk to provide battery backup to the VDSL modem to provide broadband access to battery devices such a tablets, laptops and smartphones, and access for a POTS handset plugged into the ATA port.

The supplied modem includes a 12V DC power pack rated at 2A.

Above, measurement of the current drawn averages around 0.5A with all features running (though it may draw more current during phone ringing). Continue reading Backup for NBN VDSL access

Last update: 23rd October, 2016, 11:17 AM

Backup options for NBN VDSL access

The change from Telstra ADSL to NBN VDSL drops the POTS line that gave telephone access independent of premises power.

Telephony is now provided by an ATA integrated into the VDSL modem, and dependent on mains power.

Above, a pic of an NBN FTTN cabinet from NBN’s website, and showing batteries in the bottom layer.

The supplied modem includes a 12V DC power pack rated at 2A.

Above, measurement of the current drawn averages around 0.5A with all features running (though it may draw more current during phone ringing). Continue reading Backup options for NBN VDSL access

Last update: 18th October, 2016, 12:53 PM

Toshiba alkaline AA leakage problems

I have used Toshiba alkaline cells in several sizes for many years (decades) and had not encountered one leaked cell… however in the last few months I have found 8 AA cells that have leaked in different devices.

The leakage has always had the same failure.

Above is a view of the -ve end of the battery, ground through to expose the inner structure.

The failed batteries have leaked corrosive electrolyte, and they have all split around the circumference of the battery in the region indicated by the red arrow above. The split is common half way or more around the cell, the green seal and remnant of the rolled over case is there, split away from the main case and covered in corrosive electrolyte residual.

This is not a failure of the green seal material, but rather the case fails.

It fails either due to internal corrosion, os weakness of the forming process. It is not clear that this area should be exposed to electrolyte anyway, so the corrosion might result from some other internal failure that releases electrolyte.

Enough reason to remove them from all devices and NEVER use these cells again.

Last update: 12th September, 2016, 5:43 PM

Silver vs alkaline button cells

I purchased a new digital caliper recently (no, they are NOT vernier calipers, though modern usage seems to have misused the term vernier to the point of it having no value).

A pic of the back reveals their recommendation for a battery, it is in the upper right corner of the pic “Battery 1.55V”. This is really subtle and a departure from previous practice of marking them more clearly SR44.

The nominal voltage of a silver button cell is 1.55V, an alkaline is 1.5V. Continue reading Silver vs alkaline button cells

Last update: 27th June, 2016, 10:26 AM