Anyone who’s manned a hackerspace booth at an event knows how difficult it can be to describe to people what a hackerspace is. No matter what words you use to describe it, nothing really seems to do it justice. You simply can’t use words to make someone feel that sense of accomplishment and fun that you get when you learn something new and build something that actually works.

[Derek] had this same problem and decided to do something about it. He realized that in order to really share the experience of a hackerspace, he would have to bring a piece of the hackerspace to the people.  That meant getting people to build something simple, but fun. [Derek's] design had to be easy enough for anyone to put together, and inexpensive enough that it can be produced in moderate quantities without breaking the bank.

[Derek] ended up building a simple “optical theremin”. The heart of this simple circuit is an ATTiny45. Arduino libraries have already been ported to this chip, so all [Derek] had to do was write a few simple lines of code and he was up and running. The chip is connected to a photocell so the pitch will vary with the amount of light that reaches the cell. The user can then change the pitch by moving their hand closer or further away, achieving a similar effect to a theremin.

[Derek] designed a simple “pcb” out of acrylic, with laser cut holes for all of the components. If you don’t have access to a laser cutter to cut the acrylic sheets, you could always build your own. The electronic components are placed into the holes and the leads are simply twisted together. This allows even an inexperienced builder to complete the project in just five to ten minutes with no complicated tools. The end result of his hard work was a crowded booth at a lot of happy new makers. All of [Derek's] plans are available on github, and he hopes his project will find use at Makerfaires and hackerspace events all over the world.

Read more on MAKE

Read more on MAKE

Read more on MAKE

Read more on MAKE

Read more on MAKE

Electrical engineer Chris Gammell has spent almost a year creating his new online electronics program called “Contextual Electronics“, and we’re excited to share this with our readers. You may have heard of Chris from his regular successful podcast with Dave Jones  – “The Amp Hour“.

Chris has the knowledge and expertise to take electronic ideas from simply that – an idea, right through to production. And by participating in his Contextual Electronics program you can learn the required skills to do this as well. Chris gives us a quick introduction in this video.

Contextual Electronics is a new program aimed at electronics enthusiasts who are ready to take their Arduino (or similar platform) skills to the next level. The first session of the course is an 8 week program that will teach you how to design a large, multi-function Arduino shield using KiCad, the open source CAD software.

It will also show you all of the design decisions that go into making the project. Here are some of the sub-circuits included in the 4-layer PCB design:

• High level signals measurement using op-amps

• Power supply output

• Relay control

• LED driver circuitry

• Current source output

The course has a large community component, so you will be grouped with others learning at the same time, regardless of where you’re located in the world. The goal of the course and the community aspect is to make you more confident designing a project so you can go and design your own.

Future sessions of the course will also go over building, troubleshooting and coding for the shield described above. There is also a free short course that you can review to give you an idea of Chris’ methods and what the Contextual Electronics program will be like.

Additional courses will be developed using other popular development boards, including the Raspberry Pi and BeagleBone. For a more in-depth introduction, check out this video.

Frankly the program will help all of you who are ready to take your ideas and projects off the breadboard and into finished products, and with the guidance available with the program and the use of open-source tools you’ll be up and making things you can be proud of showing to friends or even potential employers. For more information about the program, and to sign up – visit the Contextual Electronics program website.

And if you enjoyed this article, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop”.

The post Learn electronics with Chris Gammell and “Contextual Electronics” appeared first on tronixstuff.

Introduction

Slowly we’re working through the stock of old kits, and in this article we have the “Fluorescent Lamp” simulator from Talking Electronics. To save repeating myself you can read more about Talking Electronics here and watch interviews of the founder Colin Mitchell here.

So why would you want to simulate a fluoro’ tube anyway? Model railways! When your model world moves from day to night, it’s neat to have street lights and so on “flicker” on just like the real thing. And thus you can create this effect as well. It can drive incandescent lamps up to 12V, and allowing it to be powered easily from most layouts.

The kit was originally described in the Talking Electronics book “Electronics for Model Railways” (volume 1) which was full of useful and interesting electronics to liven up any layout. The book may now out of print however at the time of writing this you can download or view most of the projects from the index column of the Talking Electronics website… or contact Talking Electronics if they have any copies of the book (or kit) to sell.

Assembly

Time was not kind to the kit, to be frank it was surprising to find one at all:

(Just a note for any over-enthusiastic readers, Talking Electronics is no longer at the address on the bag shown above). However it was complete and ready for assembly. The PCB has a silk-screen with the required component placement information, polarities and so on – a first for the time:

The instructions and “how it works” are not included with the kit as you were meant to have the book, however TE have made them available as a separate download (.pdf) . The kit included everything required to get started, and there’s an LED which replicates the effect so you can test the board without having to watch the connected bulb (which may be a distance away). Finally an IC socket is included

The actual assembly process was very straight forward, which simply required starting with the low-profile components and working up to the large ones:

The only problem with the PCB was the holes – looks like only one drill size had been used (apart from the mounting holes) which made getting that rectifier diode in a little tricky. Otherwise it was smooth sailing.

Not having a model railway at the moment left me with the simple example of the onboard LED and a small incandescent globe to try with the circuit. You can see the kit working in this video.

John – Why do you publish these “Old Kit Reviews”?

They’re more of  a selfish article, like many electronics enthusiasts I have enjoyed kits for decades – and finding kits from days gone by is a treat. From various feedback some of you are enjoying them, so they will continue for fun and some nostalgia. If you’re not interested, just ignore the posts starting with “Old”!

Conclusion

For a kit from the mid-1980s, this would have solved the problem neatly for model railway enthusiasts. By using two or more of the kits with different capacitor values, many model lights could blink on with seemingly random patterns. However it’s 2014 so you could use a PIC10F200 or ATtiny45 and reduce the board space and increase the blinking potential.

Nevertheless, it was an interesting example of what’s possible with a digital logic IC. Full-sized images and a lot more information about the kit are available on flickr. And if you enjoyed this article, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a third printing!) “Arduino Workshop”.

The post Old Kit Review – Talking Electronics Fluorescent Simulator appeared first on tronixstuff.

Introduction

This is the second of three articles that will examine the LM391x series of LED driver ICs. The first covered the LM3914, this will cover the LM3915 and the LM3916 will follow. The goal of these is to have you using the parts in a small amount of time and experiment with your driver ICs, from which point you can research further into their theory and application.

Although these parts have been around for many years, the LM3915 isn’t used that much however for the sake of completeness we’re writing the tutorial. The LM3915 offers a simple way to display a logarithmic voltage level using one or more groups of ten LEDs with a minimum of fuss. If you’re wanting to make a VU meter, you should use the LM3916 which we will cover in the final instalment of this trilogy.

Instead of having each LED represent a voltage level as with the LM3914, each LED connected to the LM3915 represents a 3 dB (decibel) change in the power level of the signal. For more on decibels, check out Wikipedia.

To display these power level changes we’ll run through a couple of examples that you can use in your own projects and hopefully give you some ideas for the future. Originally by National Semiconductor, the LM391X series is now handled by Texas Instruments.

Getting Started

You will need the LM3915 data sheet, so please download that and keep it as a reference. First – back to basics. The LM3915 controls ten LEDs. It controls the current through the LEDs with the use of only one resistor, and the LEDs can appear in a bar graph or single ‘dot’ when in use. The LM3915 contains a ten-stage voltage divider, each stage when reached will illuminate the matching LED (and those below it in level meter mode).

Let’s consider the most basic of examples (from page two of the data sheet) – a simple logarithmic display of voltage between 0 and 10V:

After building the circuit you can connect a signal to measure via pin 5, and the GND to pin 2. We’ve built the circuit exactly as above on some stripboard for demonstration purposes, with the only difference being the use of an 8.2kΩ resistor for R2:

To show this in action we use a signal of varying AC voltage – a sine wave at around 2 kHz. In the following video, you can see the comparison of the signal’s voltage against the LEDs being illuminated, and you will see the logarithmic voltage increase represented by the LEDs:

We used the bar display mode for the voltage increase, and the dot display mode for the voltage decrease. Did you notice that during the voltage decrease, the LEDs below the maximum level being displayed were dim? As the signal’s voltage was varying very quickly, the change in the LED’s location is a blur due to the speed of change. In the video below, we’ve slowed the frequency right down but kept the same maximum voltage.

Well that was a lot of fun, and gives you an idea of what is possible with the LM3915.

Displaying weaker signals

In non-theoretical situations your input signal won’t conveniently be between 0 and 10 V. For example the line level on audio equipment can vary between 1 and 3V peak to peak. For example, here’s a random DSO image from measuring the headphone output on my computer whilst playing some typical music:

Although it’s an AC signal we’ll treat it as DC for simplicity. So to display this random low DC voltage signal we’ll reduce the range of the display to 0~3V DC. This is done using  the same method as with the LM3914 – with maths and different resistors.

Consider the following formulae:

As you can see the LED current (Iled) is simple, however we’ll need to solve for R1 and R2 with the first formula to get our required Vref of 3V. For our example circuit I use 2.2kΩ for R2 which gives a value of 1.8kΩ for R1. However putting those values in the ILED formula gives a pretty low current for the LEDs, about 8.3 mA. Live and learn – so spend time experimenting with values so you can match the required Vref and ILED.

Nevertheless in this video below we have the Vref of 3V and some music in from the computer as a sample source of low-voltage DC. This is not a VU meter! Wait for the LM3916 article to do that.

Again due to the rapid rate of change of the voltage, there is the blue between the maximum level at the time and 0V.

Chaining multiple LM3915s

This is covered well in the data sheet, so read it for more on using two LM3915s. Plus there are some great example circuits in the data sheet, for example the 100W audio power meter on page 26 and the vibration meter (using a piezo) on page 18.

Conclusion

As always I hope you found this useful. Don’t forget to stay tuned for the final instalment about the LM3916. And if you made it this far – check out my new book “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

The post Tutorial – LM3915 Logarithmic Dot/Bar Display Driver IC appeared first on tronixstuff.

Introduction

This is the second of three articles that will examine the LM391x series of LED driver ICs. The first covered the LM3914, this will cover the LM3915 and the LM3916 will follow. The goal of these is to have you using the parts in a small amount of time and experiment with your driver ICs, from which point you can research further into their theory and application.

Although these parts have been around for many years, the LM3915 isn’t used that much however for the sake of completeness we’re writing the tutorial. The LM3915 offers a simple way to display a logarithmic voltage level using one or more groups of ten LEDs with a minimum of fuss. If you’re wanting to make a VU meter, you should use the LM3916 which we will cover in the final instalment of this trilogy.

Instead of having each LED represent a voltage level as with the LM3914, each LED connected to the LM3915 represents a 3 dB (decibel) change in the power level of the signal. For more on decibels, check out Wikipedia.

To display these power level changes we’ll run through a couple of examples that you can use in your own projects and hopefully give you some ideas for the future. Originally by National Semiconductor, the LM391X series is now handled by Texas Instruments.

Getting Started

You will need the LM3915 data sheet, so please download that and keep it as a reference. First – back to basics. The LM3915 controls ten LEDs. It controls the current through the LEDs with the use of only one resistor, and the LEDs can appear in a bar graph or single ‘dot’ when in use. The LM3915 contains a ten-stage voltage divider, each stage when reached will illuminate the matching LED (and those below it in level meter mode).

Let’s consider the most basic of examples (from page two of the data sheet) – a simple logarithmic display of voltage between 0 and 10V:

After building the circuit you can connect a signal to measure via pin 5, and the GND to pin 2. We’ve built the circuit exactly as above on some stripboard for demonstration purposes, with the only difference being the use of an 8.2kΩ resistor for R2:

To show this in action we use a signal of varying AC voltage – a sine wave at around 2 kHz. In the following video, you can see the comparison of the signal’s voltage against the LEDs being illuminated, and you will see the logarithmic voltage increase represented by the LEDs:

We used the bar display mode for the voltage increase, and the dot display mode for the voltage decrease. Did you notice that during the voltage decrease, the LEDs below the maximum level being displayed were dim? As the signal’s voltage was varying very quickly, the change in the LED’s location is a blur due to the speed of change. In the video below, we’ve slowed the frequency right down but kept the same maximum voltage.

Well that was a lot of fun, and gives you an idea of what is possible with the LM3915.

Displaying weaker signals

In non-theoretical situations your input signal won’t conveniently be between 0 and 10 V. For example the line level on audio equipment can vary between 1 and 3V peak to peak. For example, here’s a random DSO image from measuring the headphone output on my computer whilst playing some typical music:

Although it’s an AC signal we’ll treat it as DC for simplicity. So to display this random low DC voltage signal we’ll reduce the range of the display to 0~3V DC. This is done using  the same method as with the LM3914 – with maths and different resistors.

Consider the following formulae:

As you can see the LED current (Iled) is simple, however we’ll need to solve for R1 and R2 with the first formula to get our required Vref of 3V. For our example circuit I use 2.2kΩ for R2 which gives a value of 1.8kΩ for R1. However putting those values in the ILED formula gives a pretty low current for the LEDs, about 8.3 mA. Live and learn – so spend time experimenting with values so you can match the required Vref and ILED.

Nevertheless in this video below we have the Vref of 3V and some music in from the computer as a sample source of low-voltage DC. This is not a VU meter! Wait for the LM3916 article to do that.

Again due to the rapid rate of change of the voltage, there is the blue between the maximum level at the time and 0V.

Chaining multiple LM3915s

This is covered well in the data sheet, so read it for more on using two LM3915s. Plus there are some great example circuits in the data sheet, for example the 100W audio power meter on page 26 and the vibration meter (using a piezo) on page 18.

Conclusion

As always I hope you found this useful. Don’t forget to stay tuned for the final instalment about the LM3916. And if you made it this far – check out my new book “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.