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.

toshibaaa03Above 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.

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).

IMG_1591

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

PAROT with transformerless power supply and 230V AC relay

This article documents an implementation of PAROT (Power Amplifier Run On Timer) using Transformerless power supply for PAROT.

This PAROT uses a 230V AC relay for 230V mains switching and includes PTT switching using an FOD852 opto coupler.

The intended application is to control power to a valve PA, providing programmable heater delay, and cool down delay of power off.

Parot105

Above is the electronics built on a small piece of Veroboard. This one uses a 0.47µF cap as the power supply current requirements are a little lower than for the SSR. Continue reading PAROT with transformerless power supply and 230V AC relay

PAROT with transformerless power supply and 10A SSR

This article documents an implementation of PAROT (Power Amplifier Run On Timer) using Transformerless power supply for PAROT.

This PAROT uses a 10A SSR for 230V mains switching and does not include PTT switching, but space exists for a FOD852 opto coupler for PTT switching.

The immediate application is to control my main station power supply so that if it has been in use, is hot and fans are running, the PAROT provides in this instance a 5min cool down before powering down.

Parot100Above is the electronics built on a small piece of Veroboard.

Parot101Above is the copper side of the Veroboard. The layout is designed to accomodate another implementation using a small Triac to switch a 230V AC relay. The board has been given a heavy coat of acrylic PCB lacquer to improve voltage withstand.

The PAROT is assembled inside a small die cast aluminium box with stick-on rubber feet.

Parot102Above is a view of the interior of the box. A 430V MOV is connected across the SSR output terminals, it is not clear whether the device has internal protection (Chinese product, very brief data). The LED / momentary switch on the right is the only control and indicator for PAROT operation. Note that because of the transformerless power supply, everything inside the box is potentially at mains voltage… a fact that must be kept in mind when working on it. An isolation transformer is a worthwhile tool for working on these type of things. Continue reading PAROT with transformerless power supply and 10A SSR

Transformerless power supply for PAROT

This article documents design of a capacitive transformerless power supply for operating low voltage, low power logic from power mains. The intended application is PAROT (Duffy 2013), though it has potentially wider application.

(Microchip 2004) gives a method for design of a capacitive transformerless power supply for operating low voltage, low power logic from power mains. The equations seem simplistic for a circuit whose apparent simplicity belies the complexity of an optimal design that properly tolerates supply voltage and load variations. For that reason, a SPICE simulation was used to refine a design.

The immediate application is for the PAROT chip driving a 40A SSR.

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Above is measured characteristic of a Fotek 40A SSR, it seems typical of several similar types on hand. It appears that much smaller SSRs in the 2A range require fairly similar current. Continue reading Transformerless power supply for PAROT

Variac refurb

I purchased a Yokoyama 5A Variac quite some years ago which was unsafe as purchased (with a current Test’nTag tag) and boxed up for repair / restoration.

It is needed for a current project, so time to fix it!

variac01

Above is the terminal block of the Variac. The defects include exposed input active and neutral terminals, exposed single insulated conductors, and the earth terminal has no spring washer or like and the screw also secures the resilent plastic P clip so it does not provide a reliable low resistance independent connection to the frame. There is no sign that there was ever a cover for this terminal block. It is noted that the terminal markings have been somewhat defaced.
Continue reading Variac refurb

An Emergency Stop switch for the mill

In a non-thinking moment, I had an accident with the mill because the head had not been clamped fully. I found myself fumbling for the power switch and the incident reinforced the need to fit an emergency stop button. I had procured parts for this a long time ago, it was time to put them to use!

ES01

Above is an inexpensive emergency stop button from eBay, about $6 including the box. This switch had NC and NO contact sets, for this application only the NC set is used.  A gland is used in the bottom of the box to let a 3 core 1mm^2 flex into the box. Continue reading An Emergency Stop switch for the mill

Ultrafire XML-T6 LED torch – a fix for the dysfunctional mode memory ‘feature’

On review of the Ultrafire XML-T6 torch, I found the mode switching / mode memory so dysfunctional that it rendered the torch useless in my evaluation.

XML-T6This article describes a work around  that makes the thing usable (IMHO). Continue reading Ultrafire XML-T6 LED torch – a fix for the dysfunctional mode memory ‘feature’

Fridge / freezer setup

The operating temperatures of refrigerators and freezers used for food storage is important to safe storage of food and to minimisation of energy costs.

The US FDA recommends the refrigerator should be set to 40F (4.4°) and the freezer to 0F (-17.8°).

Temperatures vary inside the cabinets, and they vary over time with opening and closing doors, and introduction of warmer goods for storage.

Many spot temperature checks are helpful but they don’t provide a very complete picture, and opening the door to make measurements disturbs the very thing being measured. Continue reading Fridge / freezer setup