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.
Above is the electronics built on a small piece of Veroboard.
Above 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.
Above 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
Power Amplifier Run On Timer (PAROT) (Duffy 2013) reported some measurements of the voltage withstand of Veroboard. Voltage withstand between tracks was observed to be just over 1400Vpk.
This article reports some further measurements of genuine Vero strip board.
Above is the test piece. Continue reading Voltage withstand of Vero strip board
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.
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
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!
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
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!
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
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.
This 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’
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
Claims of performance of LED torches become more extravagant by the month it seems.
Above is an Ultrafire XML-T6 LED torch purchased on eBay for about A$25 posted. The seller claims “CREE T6 2000lm LED Zoomable Torch Flashlight 2 x 18650 4200mah AAA Batteries”. Continue reading Ultrafire XML-T6 torch review
I purchased a torch (flashlight) on eBay recently. It was described as using CREE T6 LED array, and supplied with two 4200mAh 18650 Li-ion rechargeable batteries with charger for A$25 inc post.
Above, the cells are clearly marked 3000mAh, way short of the advertised 4200mAh… but what is their actual capacity.
Above are the results of discharge tests, the first digit is the cell number and the second is the test. The first test is charged with the supplied charger, the second test is with my charger. Continue reading Chinese 18650 Li-ion cells – Ultrafire capacity test
Further to 18650 Lithium Ion cells on eBay I purchased a pair of Panasonic NCR18650B cells, nominal 3400mAh, from an Australian supplier for about A$22 posted.
Above is a pic of a cell.
Above is a zoomed in view of the same pic with increased contrast. The feint quality control code printed on the underlying steel container is visible. It is usually visible through the jacket on genuine Panasonic cells.
It is always hard to know whether the product is genuine, the Chinese are better at copying the looks than the internals.
The cell was charged, then discharged at 1C on a battery analyser.
Above is the first three discharge cycles, the cell achieved just under 3000mAh to 2.8V, about 93% of datasheet rated capacity of 3200mAH, 85% of the advertised nominal 3400mAh capacity.
The actual discharge curve is fairly similar to the 1C curve from the datasheet.
These cells look more promising than the GTL red 5300mAh cells previously evaluated.