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DIY Hobby Electronics

LED Bar Graph With Transistors

LED bargraph thumbnail

How to build an LED bargraph display using transistor drivers where the number of LEDs illuminated is determined by the input voltage to the circuit. This circuit can be used to indicate temperature or water level or anything that can be converted to a voltage level.

There are a number of integrated circuits and modules available that are designed specifically for led bar graphs but if your junk box looks like mine then you probably don't have one. What if you want to build a bar graph today and don't have the right chip? I always have a small stock of transistors, diodes and resistors to hand just like most other hobbyists. So if I can build something out of these basic components then I can get the circuit working in an hour or two. Why don't you give this one a try. More...

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Sony Vaio Fan replacement

My Sony Vaio laptop was 2 years old when the cooling fan started to become noisy. Normally you would hear a faint whirring noise with a note that changed as the temperature control system altered the fan speed. This had become a noisy rattly sound that was quite objectionable.

So I ordered a replacement fan and set about the daunting task of changing it in my Vaio. As it turns out the process was not as difficult as I had expected it to be which was quite a relief. This is how I did it... More...

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Dremel Multitool - How To Use

Dremel Multitool with cutter Since I got a Dremel not too long ago I've found so many uses for it that I wonder how I ever managed without it. Most of my work is software but recently I've been asked to build quite a few prototypes for people. They may be based on an Arduino or a Raspberry Pi but every project needs a box or enclosure to keep the electronics tidy and safe. The Dremel is ideal for cutting circuit boards or making irregular holes in enclosures. Let me show you some of the things I've been using it for. More...

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Easy Project Power Supply For Raspberry Pi & Beaglebone

DC-DC Buck converter 12 Amp

Using a Buck switching power converter makes powering all the different parts of your project a breeze. Do you need 12V for a display and 5V for your Raspberry Pi and Arduinos but you don't want multiple supplies plugged into the wall? One of these high powered converters could be the solution to your problem. More...

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Raspberry Pi UPS

Battery + Diode for very simple UPS

Small and inexpensive microcomputers like the Raspberry Pi and Beaglebone are increasingly finding applications requiring unattended operation. You can now deploy an affordable solution to all kinds of monitoring and control applications using computers that fit in your pocket. But there is a catch. Computers need to be shutdown in an orderly fashion before power is removed to avoid corruption of the file system which can potentially render it useless. So what happens if there is a power outage or someone removes the power by mistake?

There are two ways to minimise the possibility that your raspberry Pi becomes as useful as a house brick. One way is to ensure that power is never denied to the computer should the mains power fail. Or you can detect a power fail condition and have the computer shut itself down until power returns. This series of articles looks at a variety of simple solutions to this problem. More...

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Long Time Delays With A 555 Chip

555 circuit I've been looking for a simple, low power, method to generate long time delays so that I can power up a datalogger at regular intervals to take measurements then shut it off again to save battery. I found that the humble 555 timer integrated circuit is more than up for this challenge. More...

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A Power Off Delay For Computer Shutdown

Long delay circuit Cheap microcomputer boards like the Raspberry Pi and the Beaglebone are finding applications in many places. They bring breathtaking computer power to seemingly simplistic tasks opening up a world of possibilities. But they are microcomputers and you can't simply switch them off without performing an orderly shutdown. If you do you risk corrupting the file system and rendering the device unusable. More...

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Raspberry Pi Beginner Projects: Setting Up

Raspberry Pi board legend

Get your Raspberry Pi setup and ready to develop projects. If you haven't seen what this little baby can do yet then you are in for a treat. Find out how to download and flash an operating system onto an SD card. Learn how to connect it up then communicate with it remotely as if you where there. Connect it into your local network so that you can share files. More...

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Getting Started With Electronics Review

Book cover If you are a complete beginner to electronics then this is the book for you. It takes you right from the time that you had your first curious thought about how things work right through to building your own circuits on breadboards. There's no time wasted getting there either. It's a no nonsense, straightforward guide to getting started with your hobby without taxing you to understand loads of theory. More...

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How To Measure Output Impedance The Easy Way

Z is for Impedance

Output impedance can seem a bit like black magic until you realize that it's really quite simple. Here is an easy yet effective way of measuring the output impedance of almost any circuit. I've avoided turning this into a full-on mathematical treatment of impedance that would bore you to tears. Instead I give you an easy to understand practical feel to the problem instead.

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