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There are many approaches to the problem of activating a light when it becomes dark, and a recent Design Idea covers this topic (Reference 1). Some approaches require a dc power supply and an electromechanical relay, but a better approach involves feeding the device directly from the ac line, minimizing the number of components  ( Figure 1 ). Figure 1. The photoresistor activates the TRIAC and the load when darkness falls. The heart of the device is a light-sensitive cadmium-sulphide resistor, PR, with a resistance of approximately 200 kΩ in the dark and decreasing to a few kilohms in the light. PR and capacitor C1 form an ac-voltage divider. In daylight, the voltage across PR is too low to generate the required gate-trigger current to turn on bidirectional ac switch Q1, thus keeping the load – usually a lamp – off. When it becomes dark, PR’s resistance rises, resulting in an increase in the TRIAC’s gate current that triggers the TRIAC and lights the lamp. The circuit uses inexpens...

This article investigate the practical and theoretical fundamentals of electronics. It examines how electrons move and how we measure them; how circuits work and what happens when they fail. You will also learn a bit about LED’s. [ ]

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This is a project of Gentle Touch Circuit Diagram . Consumer appliances these days hardly ever have a proper mains switch. Instead, appliances are turned on and off at the touch of a button on the remote control, just like any other function. This circuit shows how a device (as long as it does not draw too high a current) can be switched on and off using a push button. The approach requires that a micro controller is already available in the circuit, and a spare input port pin and a spare output port pin are required, along with a little software. When power is applied T1 initially remains turned off. When the button is pressed the gate of T1 is taken to ground and the p-channel power MOSFET conducts. The micro controller circuit is now supplied with power. Within a short period the micro controller must take output PB1 high. This turns on n-channel MOSFET T1 which in turn keeps T1 turned on after the push-button is released. Now the micro controller must poll the state of the push-but...

The LM3909 is an integrated circuit (IC) which will flash a light-emitting diode (LED). Using only two extra components and a battery, the circuit is cheap and has a very low current drain from a 1.5 V cell. The circuit can be used as a novelty flasher, an indicator for a dummy alarm bell box, or it could be attached to a torch so that it could be found easily in the dark! The simple circuit Led Flasher with the LM3909 IC Diagram Assembly The circuit can be built on a small piece of Veroboard (the piece shown in Figure 2 measures 15 holes by 10 strips). Using such a board, follow these instructions. 1. Depending on how far away you want the LED from the circuit board, solder a length of insulated wire to each lead of the LED. Use different colours of insulation – say, red and black, connecting the red lead to the anode (a) lead (the longer one) of the LED, and the black one to the cathode (k). Figure 2 shows these leads. 2. Cut the copper tracks as shown in Figure 2, using a 3 mm (1⁄8 ...

There are very few good, original movies these days. Most of what hits the silver screens are prequels as well as sequels of a particular franchise, and the audience continue to lap it up regardless. Well, I guess the same can be said of hardware, especially in the consumer electronics realm – narrowing it down to portable devices like smartphones and tablets. From the Samsung Galaxy S, we have seen it “grow” to end up at the Galaxy S4 at the moment, while the iPhone has ended up as the iPhone 5 till today, with whispers of an iPhone 5S or iPhone 6 on the way. The Asus-manufactured Nexus 7 tablet is no different, and it is all set to embrace a next generation model, simply known as the new Nexus 7 . Just what kind of hardware can you expect this sequel to carry? For starters, this 7” tablet is touted to boast of the highest resolution for a 7” tablet in the world – at 1,920 x 1,200 pixels on its 10-point touch IPS panel at 323ppi pixel density. Apart from that, a quad-core 1.5GHz S4 P...

Today we have a guest post by my good friend Adam. I gave him some advice and tips, but he did all of the work himself. I’ll let Adam take it from here: “I found this guitar at the bottom of my in-laws’ stairwell. It was being thrown out. When I touched the gig bag it was in, my fingers came away black with dust and grime yet inside was this near perfectly clean guitar. I did a bit of a quick clean and initial set up but now it’s time to get serious and get her playing and looking right. She’s an Epiphone Strat copy. I’d expect Scarlet to be getting on for 18-20 years old too. Further search reveals it to be an Epiphone S310 Batwing Stratocaster. This large cavity was what I was hoping for rather than the intricately routed ones on Fenders and Squires. It will make coating the cavity easier with copper sheeting. It also means I may be able to buy a Fender tortoiseshell guard. The pickups were set in different positions to a Fender and I was worried that if the cavity was shaped like a ...

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. [ ]

Most photovoltaic cells are made of silicon chip above which there resides a very thin layer of noble metal through which around 1% of photon particles enter the material and activates electron flow. Here I’m showing how to make one simple solar panel using transistor. [ ]

In lighting, the electrical device that regulates the current passing through the bulb filaments and, thereby, the amount of light emitted from the lighting instruments. A rheostat that varies the current through an electric light in order to control the level of illumination A control that regulates light levels. Electronic controls that allow  lighting to fade up or down slowly, as opposed to being on or off only. An instrument used to change the voltage of lights on the set, regulating in this way thier intensity. A device that controls levels of light by varying the electric current.a device in the electrical circuit used for varying the brightness of lamps in a lighting installation. Device which provides adjustable voltage to a lighting fixture to control light output. Can also be a term to refer to a mechanical device, such as a shutter, that controls output Dimming controls are ideal for any number of rooms because they allow you to change design the lighting to suit each m...