DIY Electronics Projects

This started out as an investigation into how long I could run an Arduino on a small battery and still get it to do something useful. I had to choose the right Arduino board and figure out how to use the 'SLEEP_MODE_PWR_DOWN' mode.

With a little bit of gentle hacking of the board, editing a file in the Arduino IDE and flashing the fuses in the Arduino I managed to get the power consumption down to less than 5µA. At this level a 3v button cell should last for years but I still needed to make it do something.

"A christmas decoration" I said. I will make an LED icicle that drips every few seconds. Perfect I thought. Read on to find out how you can build one too. More...

One of the most versatile of the Arduino family is the Pro-Mini. Its tiny footprint and low power make it ideal for many battery powered devices. However it lacks a USB port and an ISP programming connector which makes it a little more difficult to program.

You can either attach an FTDI USB to serial converter and program it using the bootloader like other Arduinos or you can program it using the ISP programmer built onto this break out board. Don't worry, the ISP programmer is no more difficult to use than the bootloader and it also allows you to reprogram the bootloader and the configuration fuses. This is most important when configuring the board to run at very low current consumption and you can't do that with the bootloader. More...

The Arduino Pro-Mini is a tiny microcontroller with similar features to that of the UNO. It has a bootloader for uploading programs but unlike the UNO it doesn't have a USB interface so you need to use a USB to serial adapter to use it.

Why not use an In System Programmer (ISP) instead? You can use a cheap UNO as an ISP and you can then program the bootloader and fuses as well as the application program. Sounds like a win-win to me. More...

Driving an LED from a 5v microcontroller is no problem. Flashing a red, blue, green or yellow LED should be possible even with a microconroller running at 3v but what if you want to drive a white LED that doesn't strart to illuminate until it's voltage gets to about 3.1v?

Worse still what if you are designing a battery operated device and you wanted to squeeze every last second of juice from the battery by allowing the voltage to drop to the minimum the microcontroller will work at? This would be 1.8v in the case of an Arduino chip which is way short of a glowing white LED. The solution is to add a voltage multiplier to the controller output driving the LED. More...

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...

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...

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...

Build a simple one transistor amplifier circuit that you can use in many projects where you need to amplify small signals. A circuit like this could form the basis of a high quality audio preamplifier and it only uses five components. There is a catch though. Find out what it is in this project article.

You are going to need test equipment. A multimeter is essential and cheap but it will only take you so far. What you really want is a digital oscilloscope, the ultimate tool of any electronics engineer or hobbyist.

Make this the next project that you build and you will be able to use it to fault find and explore all of your future circuits. But oscilloscopes are expensive, aren't they? Yes they can be but this is a solution that everyone can afford.

How to build a simple but useful strobe based tachometer using an Arduino Uno, an LCD/Keypad shield and a few transistors, LED's and resistors. Short pulses are generated with a simple Arduino sketch and used to drive a bank of LED's. This produces short regular pulses of light which when synchronized with the speed of a fan or motor or other rotating object, makes the moving object appear to be standing still. When this happens the light pulse rate is equal to the RPM of the object. More...