This GU10 LED spot light is cheap (£3 including postage) and bright. But it’s also lethal! There’s a 50% chance of putting live mains within a few microns of the metal casing (which is what you’ll be holding when you insert it) and there’s no earth to protect you. It’s like playing Russian Roulette with 240v AC mains. This sort of thing gives new technology a bad name. Avoid it if you want to stay alive.
Dangerous GU10 LED Spot Light is Cheap and Bright but could Kill You – Seriously - [Link]
A project with only 2 parts, but is great for addressing an everyday situation that is irritating at best and dangerous at worst. This circuit protects the bulb in flashlights from high switch-on current to make the bulb last longer.
For a standard incandescent flashlight, this is a easy little modification make your flashlight bulbs last longer. High powered flashlights typically run their bulbs hot to get a brighter light from them. They also have a much lower on-resistance when cold, so that when you turn them on, the bulb passes a much higher current than it was designed for. This is why the most common time for a bulb failure is when turning it on.
The transistor and resistor limit the current while turning on the circuit and protect the bulb from an initial high current turn on. A simple resistor in series with the bulb might be a tempting option, but there are a couple problems with that approach. Just adding a resistor would reduce the voltage available to the bulb, and aid longevity, but that would reduce the brightness. The resistor would also be wasting energy getting hot instead of using that energy for light. This solution is better in that it limits current at startup and wastes very little energy when in use and when off.
In this application, it might be easier to insert the batteries in the flashlight “backwards” so the circuit connections and parts have the best fit in the body of the flashlight. Flashlight design was stagnant for decades, but now there are many new technologies available, and in some cases, it can even be easy to bring some of them to an older one you already have. In addition to this circuit, you could also take advantage of newer LED and battery technology to really increase the brightness, “on” time, and lamp life of your old flashlight.
Soft Start For Flashlights - [Link]
With OLEDs approaching production maturity, Osram has announced that it is researching another technology that could change the world of lighting: light emitting foils produced in a printing process. The foils are based on light-emitting electrochemical cells made from organic materials, known as organic light-emitting electrochemical cells (OLECs). Although similar to OLEDs, they have a conductive and light-emitting layer containing a liquid material instead of a solid material. This active layer contains freely mobile ions in the liquid phase. When a voltage is applied to the active layer, the ions migrate to the edge. This allows charge carriers to be injected into the layer, where they recombine to emit light in the same way as a light-emitting diode. With suitable combinations of materials, any desired color of light can be obtained. [via]
Printed Light-Emitting Foils Could Challenge OLEDs - [Link]
I really liked the idea of controlling my “Home Theatre” lights with a remote (TV or other), this would save me the exhausting task of heaving myself off the couch to turn the lights on or off.
I found one of my remotes has a spare power button, its one of those stupid “universal” remotes that comes with DVD players or TVs but only work if you have all the same brand equipment, I don’t so this made a good option for a light switch.
Remote Controlled Home Theatre Lights - [Link]
Publitek European Ed writes:
Daylight harvesting is becoming increasingly important in the design and implementation of commercial lighting systems. Being able to integrate the natural light from windows with flexible, controllable sources of lighting helps improve the work environment and cut energy bills.
Being able to have closer control of the lighting systems in a commercial environment is a key element to this strategy and energy harvesting can play an important role. Being able to have flexible placement of control pads for a commercial lighting system is an important requirement as office space is regularly reconfigured as existing clients grow and change their requirements and new clients have new requirements.
Smart Lighting in the Enterprise - [Link]
A photoflash unit is a Resistor-Capacitor circuit. It utilizes a fundamental property of capacitors. A capacitor opposes an abrupt change in the voltage and this ability of a capacitor is put to use.
Circuit design of a photoflash unit:
A photoflash unit has a simple circuit design: a high-voltage direct current (DC) supply is connected in series with a high-resistance resistor (which we’ll call ‘R1′). This resistor limits the current flow. A capacitor ‘C’ is connected in parallel with a flash lamp. The resistance ‘R2’ of a flash lamp is of small value. The circuit contains a switch between the large resistance ‘R1’ and a small resistance flash lamp ‘R2’, such that it can connect either resistance at any time during the process.
How does it work?
When the switch connects R1, the capacitor begins to become charged. The charging of a capacitor is time consuming due to a large ‘time constant’. The time constant is the product of the resistance ‘R1’ and the capacitance ‘C’, given by the following expression:
Time Constant = Resistance of large Resistance * Capacitance
T = R1*C
During the charging process, the potential of the capacitor starts rising gradually. Initially it has the value of zero but by the charging it rises to a steady value of ‘Vs’. As the voltage increases, the value of the electric current passing through it decreases from peak value to zero. This limiting of current happens due to the large resistance R1. The charging time of a capacitor is approximately equal to five times the time constant. That is;
Charging time of capacitor = 5*Time constant
The discharging process of a capacitor takes place when switch connects with the flash lamp (with small resistance ‘R2’). The low resistance of the flash lamp allows a high discharge electric current to flow in a brief period of time. The discharging time is almost five times the product of small resistance ‘R2’ and the capacitance ‘C’, given by the following relation:
Discharging time of a capacitor = 5* (R2*C)
The photoflash unit circuit emits a high current pulse of short duration during the complete charging and discharging process of this simple Resistor- Capacitor Circuit. Such an RC circuit has many other practical applications, including Radar Transmitter Tubes and Electric Spot Welding.
Ivan Sergeev writes:
This project was used as a wireless light dimmer, but in principle can be used to dim resistive loads and wirelessly turn on/off loads. The current code includes a routine to dim a light bulb in a “heartbeat” pattern, with the heartbeat frequency remotely adjustable.
The top left of the schematic shows the wall outlet (US 120VAC) being stepped down with a small transformer, then full rectified and regulated. This powers the entire board from the wall. The top right shows a microcontroller, ATmega48, its programming header, and a UART connection to the microcontroller (for debugging). The bottom right shows the XBee and its basic voltage regulation (it’s 3.3V), as well as an LED that indicates when the XBee is connected.
Wireless TRIAC dimmer - [Link]
Giorgos Lazaridis writes:
I got myself some UV-curable solder mask for my PCB workshop, and as soon as i got it, i discovered that my UV artwork transfer box is totally incapable to activate the UV paint and cure it. I began searching the net for powerful UV lamps, and then it hit me: Some months ago i uploaded a theory regarding the Cold and Hot cathode discharge lamps. During my research for these lamps i found out that they can provide directly visible light (lamps without internal coating), or they produce UV radiation. The lamps that produce UV radiation have an extra coating on their internal surface which glows when excited by the UV rays, thus producing light!
Hack a Hg Lamp to a Powerful UV Light Source - [Link]
How to Attach (or Reattach) EL Tape (Electroluminescent Tape) ElectricFeel writes – [via]
When trying to connect EL Tape, if you have worked with other electronics or EL Wire before, then this should come very easily to you. If you are familiar with most electronics but have never worked with EL Wire before, it still may come fairly easily for you as this concept is actually easier than EL Wire in most respects. Basically there are a positive and negative channel which runs the entire length of the tape. These two channels act like most electronics where you have a positive and negative and the two cannot touch. The main difference is most electronics need to have a closed loop system where the ends double back around and make a consistent flow of energy to make the electronic device work properly. For Electroluminescent products, you MUST have an open loop where the positive and negative channels (or wires) do not touch, otherwise it will short out the tape.
How to Attach (or Reattach) EL Tape (Electroluminescent Tape) - [Link]
Circuit Skills – Infrared Light @ MAKE… [via]
Infrared light may be invisible to the human eye, but its usefulness in the world of electronics is easy to see. From simple object sensors to wireless data transmission, IR emitters and detectors can be used in a variety of different ways. And their low cost and wide availability makes them a great choice for enhancing an electronics project.
Circuit Skills – Infrared Light - [Link]