Tag Archive | "dmd"

Project: Clock Four – Scrolling text clock

Introduction

Time for another instalment in my highly-irregular series of irregular clock projects.  In this we have “Clock Four” – a scrolling text clock. After examining some Freetronics Dot Matrix Displays in the stock, it occurred to me that it would be neat to display the time as it was spoken (or close to it) – and thus this the clock was born. It is a quick project – we give you enough to get going with the hardware and sketch, and then you can take it further to suit your needs.

Hardware

You’ll need three major items – An Arduino Uno-compatible board, a real-time clock circuit or module using either a DS1307 or DS3232 IC, and a Freetronics DMD. You might want an external power supply, but we’ll get to that later on.

The first stage is to fit your real-time clock. If you are unfamiliar with the operation of real-time clock circuits, check out the last section of this tutorial. You can build a RTC circuit onto a protoshield or if you have a Freetronics Eleven, it can all fit in the prototyping space as such:

If you have an RTC module, it will also fit in the same space, then you simply run some wires to the 5V, GND, A4 (for SDA) and A5 (for SCL):

By now I hope you’re thinking “how do you set the time?”. There’s two answers to that question. If you’re using the DS3232 just set it in the sketch (see below) as the accuracy is very good, you only need to upload the sketch with the new time twice a year to cover daylight savings (unless you live in Queensland). Otherwise add a simple user-interface – a couple of buttons could do it, just as we did with Clock Two. Finally you just need to put the hardware on the back of the DMD. There’s plenty of scope to meet your own needs, a simple solution might be to align the control board so you can access the USB socket with ease – and then stick it down with some Sugru:

With regards to powering the clock – you can run ONE DMD from the Arduino, and it runs at a good brightness for indoor use. If you want the DMD to run at full, retina-burning brightness you need to use a separate 5 V 4 A power supply. If you’re using two DMDs – that goes to 8 A, and so on. Simply connect the external power to one DMD’s terminals (connect the second or more DMDs to these terminals):

The Arduino Sketch

You can download the sketch from here. Please use IDE v1.0.1 . The sketch has the usual functions to set and retrieve the time from DS1307/3232 real-time clock ICs, and as usual with all our clocks you can enter the time information into the variables in void setup(), then uncomment setDateDs1307(), upload the sketch, re-comment setDateDs1307, then upload the sketch once more. Repeat that process to re-set the time if you didn’t add any hardware-based user interface.

Once the time is retrieved in void loop(), it is passed to the function createTextTime(). This function creates the text string to display by starting with “It’s “, and then determines which words to follow depending on the current time. Finally the function drawText() converts the string holding the text to display into a character variable which can be passed to the DMD.

And here it is in action:

Conclusion

This was a quick project, however I hope you found it either entertaining or useful – and another random type of clock that’s easy to reproduce or modify yourself. We’re already working on another one which is completely different, so stay tuned.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, 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.

Posted in arduino, clocks, dmd, ds1307, DS3232, freetronics, learning electronics, LED matrix, microcontrollers, projects, scrolling, time clock, timing, tutorialComments (10)

Tutorial: Arduino and the MSGEQ7 Spectrum Analyzer

This is a tutorial on using the MSGEQ7 Spectrum Analyser with Arduino, and chapter forty-eight of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 10/11/2014

In this article we’re going to explain how to make simple spectrum analysers with an Arduino-style board. (Analyser? Analyzer? Take your pick).

First of all, what is a spectrum analyser? Good question. Do you remember what  this is?

It’s a mixed graphic equaliser/spectrum analyser deck for a hi-fi system. The display in the middle is the spectrum analyser, and roughly-speaking it shows the strength of  different frequencies in the music being listened to – and looked pretty awesome doing it. We can recreate displays similar to this for entertainment and also as a base for creative lighting effects. By working through this tutorial you’ll have the base knowledge to recreate these yourself.

We’ll be using the MSGEQ7 “seven band graphic equaliser IC” from Mixed Signal Integration. Here’s the MSGEQ7 data sheet (.pdf).  This little IC can accept a single audio source, analyse seven frequency bands of the audio, and output a DC representation of each frequency band. This isn’t super-accurate or calibrated in any way, but it works. You can get the IC separately, for example:


and then build your own circuit around it… or like most things in the Arduino world – get a shield. In this case, a derivative of the original Bliptronics shield by Sparkfun. It’s designed to pass through stereo audio via 3.5mm audio sockets and contains two MSGEQ7s, so we can do a stereo analyser:

As usual Sparkfun have saved a few cents by not including the stackable header sockets, so you’ll need to buy and solder those in yourself. There is also space for three header pins for direct audio input (left, right and common), which are useful – so if you can add those as well.

So now you have a shield that’s ready for use. Before moving forward let’s examine how the MSGEQ7 works for us. As mentioned earlier, it analyses seven frequency bands. These are illustrated in the following graph from the data sheet:

freqresponse

It will return the strengths of the audio at seven points – 63 Hz, 160 Hz, 400 Hz, 1 kHz, 2.5 kHz, 6.25 kHz and 16 kHz – and as you can see there is some overlap between the bands. The strength is returned as a DC voltage – which we can then simply measure with the Arduino’s analogue input and create a display of some sort. At this point audio purists, Sheldonites and RF people might get a little cranky, so once again – this is more for visual indication than any sort of calibration device.

However as an 8-pin IC a different approach is required to get the different levels. The IC will sequentially give out the levels for each band on pin 3- e.g. 63 Hz then 160 Hz then 400 Hz then 1 kHz then 2.5 kHz then 6.25 kHz  then 16 kHz then back to 63 Hz and so on. To start this sequence we first reset the IC by pulsing the RESET pin HIGH then low. This tells the IC to start at the first band. Next, we set the STROBE pin to LOW, take the DC reading from pin 3 with analogue input, store the value in a variable (an array), then set the STROBE pin HIGH. We repeat the strobe-measure sequence six more times to get the rest of the data, then RESET the IC and start all over again. For the visual learners consider the diagram below from the data sheet:

strobing1

To demonstrate this process, consider the function

in the following example sketch:

If you follow through the sketch, you can see that it reads both left- and right-channel values from the two MSGEQ7s on the shield, then stores each value in the arrays left[] and right[]. These values are then sent to the serial monitor for display – for example:

If you have a function generator, connect the output to one of the channels and GND – then adjust the frequency and amplitude to see how the values change. The following video clip is a short demonstration of this – we set the generator to 1 kHz and adjust the amplitude of the signal. To make things easier to read we only measure and display the left channel:


Keep an eye on the fourth column of data – this is the analogRead() value returned by the Arduino when reading the 1khz frequency band. You can also see the affect on the other bands around 1 kHz as we increase and decrease the frequency. However that wasn’t really visually appealing – so now we’ll create a small and large graphical version.

First we’ll use an inexpensive LCD, the I2C model from akafugu reviewed previously. To save repeating myself, also review how to create custom LCD characters from here.

With the LCD with have two rows of sixteen characters. The plan is to use the top row for the levels, the left-channel’s on … the left, and the right on the right. Each character will be a little bar graph for the level. The bottom row can be for a label. We don’t have too many pixels to work with, but it’s a compact example:

lcdfullon

We have eight rows for each character, and the results from an analogueRead() fall between 0 and 1023. So that’s 1024 possible values spread over eight sections. Thus each row of pixels in each character will represent 128 “units of analogue read” or around 0.63 V if the Arduino is running from true 5 V (remember your AREF notes?). The sketch will again read the values from the MSGEQ7, feed them into two arrays – then display the required character in each band space  on the LCD.

Here’s the resulting sketch:

If you’ve been reading through my tutorials there isn’t anything new to worry about. And now for the demo, with sound –

That would look great on the side of a Walkman, however it’s a bit small. Let’s scale it up by using a Freetronics Dot Matrix Display – you may recall these from Clock One. For some background knowledge check the review here.  Don’t forget to use a suitable power supply for the DMD – 5 V at 4 A will do nicely. The DMD contains 16 rows of 32 LEDs. This gives us twice the “resolution” to display each band level if desired. The display style is subjective, so for this example we’ll use a single column of LEDs for each frequency band, with a blank column between each one.

We use a lot of line-drawing statements to display the levels, and clear the DMD after each display. With this and the previous sketches, there could be room for efficiency – however I write these with the beginner in mind. Here’s the sketch:

… and here it is in action:

Conclusion

At this point you have the knowledge to use the MSGEQ7 ICs to create some interesting spectrum analysers for entertainment and visual appeal – now you just choose the type of display enjoy the results. 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 fourth printing!) “Arduino Workshop”.

visit tronixlabs.com

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website.

Posted in analyser, analyzer, arduino, BLIPTRONICS, com-10468, dev-10306, education, graphic, lesson, MSGEQ7, sparkfun, spectrum, tutorial

April 2012 Competition Results

Competition over.

Posted in competition

April 2012 Competition

Competition over!

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Arduino meets Las Vegas with the Freetronics DMD

Updated 05/11/2014

Time once more to have some fun, and this time by examining the Freetronics DMD “Dot Matrix Display” available from Tronixlabs. We will look at the setup and operation of the display. In a nutshell the DMD comprises of a board measuring approximately 320mm across by 160mm which contains 16 rows of 32 high-intensity red LEDs. For example, in the off state:

Connection of the DMD to your Arduino-compatible board is quite simple. Included with each DMD is a 2×8 IDC cable of around 220mm in length, and a PCB to allow direct connection to the Arduino digital pins D6~13:

Finally the cable connects to the left-hand socket on the rear of the DMD:

You can also daisy-chain more than one display, so a matching output socket is also provided. Finally, an external power supply is recommended in order to drive the LEDs as maximum brightness – 5V at ~4 A per DMD. This is connected to a separate terminal on the rear of the board:

Do not connect these terminals to the 5V/GND of your Arduino board!

A power cable with lugs is also included so you can daisy chain the high-intensity power feeds as well. When using this method, ensure your power supply can deliver 5V at 4A  for each DMD used – so for two DMDs, you will need 8A, etc. For testing (and our demonstration) purposes you can simply connect the DMD to your Arduino via the IDC cable, however the LEDs will not light at their full potential.

Using the display with your Arduino sketches is quite simple. There is an enthusiastic group of people working on the library which you will need, and you can download it from and follow the progress at the DMD Github page and forks. Furthermore, there is always the Freetronics forum for help, advice and conversation. Finally you will also need the TimerOne library – available from here.

However for now let’s run through the use of the DMD and get things moving. Starting with scrolling text – download the demonstration sketch from here. All the code in the sketch outside of void loop() is necessary. Replace the text within the quotes with what you would like to scroll across the display, and enter the number of characters (including spaces) in the next parameter. Finally, if you have more than one display change the 1 to your number of displays in #define DISPLAYS_ACROSS 1.

Here is a quick video of our example sketch:

Now for some more static display functions – starting with clearing the display. You can use

to turn off all the pixels, or

to turn on all the pixels.

Note: turning on more pixels at once increases the current draw. Always keep this in mind and measure with an ammeter if unsure. 

Next some text. First you need to choose the font, at the time of writing there were two to choose from. Use

for a smaller font or

for a larger font. To position a single character on the DMD, use:

which will display the character ‘x’ at location x,y (in pixels – starting from zero). For example, using

results with:

Note if you have the pixels on ‘behind’ the character, the unused pixels in the character are not ‘transparent’. For example:

However if you change the last parameter to GRAPHICS_NOR, the unused pixels will become ‘transparent’. For example:

You can also use the parameter GRAPHICS_OR to overlay a character on the display. This is done with the blinking colon in the example sketch provided with the library.

Next, to draw a string (group of characters). This is simple, just select your font type and then use (for example):

Again, the 5 is a parameter for the length of the string to display. This results in the following:

Next up we look at the graphic commands. To control an individual pixel, use

And changing the 1 to a 0 turns off the pixel. To draw a circle with the centre at x,y and a radius r, use

To draw a line from x1, y2 to x2, y2, use:

To draw a rectangle from x1, y2 to x2, y, use:

And to draw a filled rectangle use:

Now let’s put those functions to work. You can download the demonstration sketch from here, and watch the following results:

Update – the DMD is also available in other colours, such as white:

So there you have it, an inexpensive and easy to use display board with all sorts of applications. Although the demonstrations contained within this article were rather simple, you now have the knowledge to apply your imagination to the DMD and display what you like. For more information, check out the entire DMD range at Tronixlabs. 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 fourth printing!) “Arduino Workshop”.

visit tronixlabs.com

Have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column, or join our forum – dedicated to the projects and related items on this website.

Posted in arduino, dmd, freetronics, LED matrix, lesson, microcontrollers, product review, review, tronixlabs, tutorialComments (0)


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