Unorthodox Fire Starting Devices

A fire plunger. Image courtesy eBay

Two gadgets for those who need to light a fire when camping or otherwise and want to show off (although a cigarette or gas lighter is perfectly adequate): A plasma lighter produces an electrical arc between two electrodes using a high voltage, generated from a rechargeable battery. The temperature of an electrical arc can reach up to 19,400 °C, so it can easily melt steel (arc welding) or light tinder for starting a fire.

A fire plunger or fire syringe is like a bicycle pump with a cylinder into which a small piece of tissue or rag is placed. To operate the device, a plunger is rapidly slammed into the cylinder and this compresses the air inside, rising its temperature by several hundred degrees, enough to ignite the tissue inside. This is the same principle on which a diesel engine works—a gas increases in temperature when it's compressed. Once the tissue ignites, the embers can be used to ignite kindling.

Like most real-world examples, a fire plunger doesn't obey Boyle's Law, Charles's Law or Gay-Lussac's Law exclusively. All of these laws of thermodynamics require one variable—temperature, pressure or volume—to be kept constant while two of the other variables change. In a fire plunger, or when pumping a car tyre for that matter, pressure, volume and temperature all change at the same time.

Gay-Lussac's law may be the one you experienced as a child if you ever threw a bottle or can into a fire and it exploded. The law states that, at constant volume, pressure is proportional to temperature. 

A plasma lighter. Image courtesy eBay.

 

Gadgets for Connecting to Old Hi-Fi Systems

Image courtesy Amazon.ie

This sort of gadget might be useful for those of you who have older hi-fi systems and want to stream music from your computer or mobile device. It's a Bluetooth receiver that has left and right, line-out outputs with RCA connectors for connecting to red and white line-in (sometimes called "Aux" ) connectors on audio equipment such as a hi-fi system. Cables are also available (or can be made up) to convert between line-out and DIN 41524, 5-pin connectors, sometimes used for auxiliary input on older equipment.

An alternative is to simply use a modern TV (which will have WIFi and Bluetooth connectivity) to generate the line-out signals for connecting to a hi-fi. Some modern TVs don't have red and white line-out connectors, just a digital optical output, however adaptors are available for converting this back to line-out for connecting to an older hi-fi system without optical input.

Hi-fis that only have phono inputs

My old Sony hi-fi from circa 1993 doesn't have twin line-in input connectors, just RCA phono connectors for the turntable. Although the connectors are physically the same as the RCA type used for line-in/line-out, phono inputs only accept low-level signals of a few millivolts (mV) generated by the cartridge on a turntable (the cartridge isn't powered and the signal isn't amplified). Apparently vinyl recordings use what's known as RIAA equalisation, low frequency sounds being attenuated during recording. The input pre-amp in a hi-fi or "stereo" that's connected to the phono input then does the reverse: cancelling the attenuation of low frequencies that was done during recording by boosting low frequencies on playback, resulting in an overall flat response. I won't explain why, but you can read more about it here.

Gadgets like this one are available that convert line level signals (from e.g. a TV) that are typically almost half a volt peak to the mV levels required by the turntable input. They also use a passive filter to attenuate low frequencies, simulating RIIAA equalisation.

Image courtesy Djbox.ie

I haven't personally used any of these converter adapters. Depending on what you pay for them, some are probably better quality than others and like like any intermediate system that converts and filters signals, noise and distortion will be added which degrades the final output. So sound quality won't likely be as good as when directly connecting line-out from a device to line-in of a hi-fi/amp.

NHK World Japan

Japan Broadcasting Corporation or Nippon Hōsō Kyōkai is a Japanese public broadcasting channel. The international version is NHK World Japan and it's an interesting channel with lots of documentaries about Japanese culture, crafts and technology, as well as news. Japan's Top Inventions is a series about the various inventions that originated in Japan. The program broadcast this evening was about how automatic door openers using PIR sensors replaced older types that used foot operated pressure switches. (I remember the novelty of coming across these for the first time in Dublin Airport in 1972. Did Woolworths have them too?)

USB Extender

Before USB, RS232 serial ports on computers had a range of up to 15 m, however USB is limited to a max cable length of 3 to 5 m, depending on data rate. If you can't use wireless and want to extend your USB connection up to 45 m, you can use one of these. The adapters are connected together using Cat 5 network cable. (I've used ordinary alarm cable, but it's supposed to be screened I think). It's only USB 1.1 standard, so not exactly for transferring lots of data fast, but could be useful for connecting to remote measuring instruments.

This product from RS extends USB up to 45 m.

Plasma Lighters

First there were gas lighters that used fairly big, now obsolete types of zinc carbon batteries for heating an incandescent filament. They didn't produce a flame, so they were usually used for lighting gas cookers and "Kosangas" type portable heaters. The gas lighters and cigarette lighters we have now incorporate a piezoelectric cell, operated by pressure suddenly applied to the cell when a trigger was squeezed. This creates a high voltage spark that ignites gas stored in the lighter. I wasn't aware of these new types of lighters though. Plasma lighters don't need gas and instead produce a plasma between the electrodes (an arc) for lighting things. Sort of like a Taser, but the electrodes are closer together so the arc is hotter. It reminds me of when I had an old induction coil out of car and use to set pieces of timber on fire with the arc. With the lights switched off, the purple glow of corona discharges at sharp points was interesting too. Corona discharge is a phenomenon that can be seen on very high voltage power lines in humid conditions or pointed objects during thunderstorms (known as St. Elmo's Fire). It's effectively a "leak" of electrons through the air at points of high electric field strength. However the leak isn't sufficient to cause a full breakdown of the air and the formation of an arc. Electrical equipment that operates at high voltage is designed to reduce the number of points and sharp edges on conductors which may cause corona effects. Corona can potentially lead to arcing or other damage. It also generates EMI radio interference.

Corona discharage on a power line. Nitromethane, CC BY-SA 3.0

Pocket Weighing Scales From Temu

Pocket scales from Temu © Eugene Brennan

Playing with my latest Temuu gadget. A pocket scales which cost less than €5. Without proper calibration weights, it's hard to tell how accurate it is, but this is what it displays with some weights I bought.
Not sure what I'll use it for 🙄. No, I'm not becoming a drug dealer, but I like measuring instruments.

There used to be a balance in our classroom in the BNS, when it was based in what is now Kilcullen Library, along with glassware and other scientific equipment, hidden away in a cupboard (including a bottle of mercury which is highly toxic). They may have dated from before the war. We never used those items though.

Some information here on the teaching of "Rural Science" and "Nature Studies" in primary schools in the early part of the 20th century. The teaching of these subjects became optional in 1934, more emphasis being placed on using the time for teaching Irish:

ELEMENTARY SCIENCE IN IRISH PRIMARY
SCHOOLS FROM THE LATE 1800s TO THE
PRESENT DAY

Some more photos of what the scales indicated for the various weights I bought.

 

Temu Magnifier That Uses a Fresnel Lens

Credit card magnifier. Photo © Eugene Brennan

My latest gadget from Temu, a credit card-sized magnifier. This is really useful and the scientific angle is that it makes use of a Fresnel lens. This type of lens is used in front of the lamps in lighthouses and also as the plastic window in PIR sensors. "Normal" spherical lenses are made from a curved piece of glass, plastic or quartz, making use of the refractive powers of the material to bend light. However they can be quite thick when used for high magnification. A Fresnel lens reduces the thickness and volume of material required by using individual elements or concentric, prismatic rings, so that magnifiers can even be manufactured in flat sheet. More info about Fresnel lenses is available on Wikipedia here.

© Eugene Brennan

First-order rotating catadioptric Fresnel lens, dated 1870, displayed at the Musée national de la Marine, Paris. Image by Rama, CeCill licence via Wikimedia Commons

How to Use USB Devices With Android Smartphones & Tablets: On-The-Go Cables

© Eugene Brennan