DIY Hobby Electronics

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...

Do you have a 5v FTDI serial adapter and a 3.3v Arduino or Raspberry Pi? You know that you can't plug the adapter directly into the 3.3v microcontroller right but did you know that it's quite possible to build a simple voltage level converter to solve the problem?

I bought a 3.3v Arduino Pro Mini compatible board for a project but I made the mistake of ordering the wrong FTDI serial adapter. I got a 5v unit instead of a 3.3v one but I needed to use it quickly so I used 3 resistors to convert the levels so that I could use FTDI adapter with the 3.3v microcontroller. I thought that you might find this little converter board useful too More...

Let me show you how servo motors work and what you need to do to drive them. There's a handy library that you can use with Android which makes things very easy called 'Servo'. But what if you need to drive the servo some other way? If that's the case then you will need to know something about how they work.

I will show you how to connect one up and write a very simple Arduino sketch to experiment with. I explain exactly what goes on inside a servomotor and I finish up with a set of oscilloscope traces. If you want to know more about servo motors then read on. 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...

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...

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...

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.