Limpkin's blog - Tag - 434mhz<div>An electronics geek blog, dedicated to sharing and open source. Check out my stores: <a href="https://lectronz.com/stores/stephanelec" hreflang="en" title="Lectronz store">EU</a> / <a href="https://www.tindie.com/stores/stephanelec" hreflang="en" title="tindie store">EU & US</a>.</div>2024-03-29T00:41:47+00:00Mathieuurn:md5:51de6a3d917257edeff5a252fe925b02DotclearIntroducing the toktoktok projecturn:md5:ced438724e6e9446086b173671623d842012-03-05T13:35:00+00:002024-03-09T11:07:53+00:00limpkinMy Projects434mhzcontact micdomotichome automationteensy<p>Hey guys! Here is the latest project I've been working on for one year now : <strong>toktoktok</strong>. And if you like it, <strong>I could really use your help</strong> :) .<br></p>
<p><img src="https://www.limpkin.fr/public/toktoktok/.logo_m.jpg" alt="Toktoktok" class="media-center" title="Toktoktok, fév. 2012"></p> <p>First, have a look at the indiegogo campaign video I made for the occasion :<br></p>
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<p>Yes, you are seeing my face for the first time :-) .<br>
So I'm gonna start by talking about the general toktoktok project idea:<br><br></p>
<h2>What is the Toktoktok Project?<br><br></h2>
<p>The Toktoktok project aims to create a <strong>simple, intuitive, and unified interface for all aspects of home automation</strong>. This product converts <strong>any surface</strong> into a touch sensitive input device for home automation purposes. To do so, I propose a cheap, simple-to-use and easy-to-implement box that only needs to be attached to a surface to make it sensitive to <strong>user interactions</strong>. This new technology is remarkable because it does not require specific indoor conditions to function and provides an intuitive input interface that anyone can use.<br>
You may ask why is that useful? Well, imagine being able <strong>to control your home within arm's reach...</strong> <br><br></p>
<h2>A Patent Free Idea!<br><br></h2>
<p>I went to the <strong>Institute of Intellectual Property</strong> in Bern, Switzerland (where Einstein was working), and found that this idea of knock detecting boxes <strong>has not been patented</strong>.<br>
Therefore, when this idea goes public, it falls <strong>into public knowledge</strong> and can't be patented anymore (well, in theory ;-) ). <br>
Everyone can then use it but also twist it!<br><br></p>
<h2>So who is it made for and how can you use it? <br><br></h2>
<p>Toktoktok is made for <strong>everyone</strong>, as it is so simple to implement. <br>
But more specifically, it is particularly suited for <strong>persons having a low-mobility</strong>.<br>
Currently, the toktoktok system is composed of toktoktok boxes, lamp/power switching sockets and RF receivers for computers.<br>
Therefore, it will allow you to:<br>
- <strong>add additional switches</strong> in convenient places<br>
- <strong>not spend 10 minutes</strong> looking for the light switch, especially if you are in the dark<br>
- <strong>switch off all electronic devices</strong> when leaving the house<br>
- <strong>control your computer music player</strong> from anywhere<br>
- <strong>quickly turn off your computer</strong> (not the hard way ;) ): this is for people (like me) that like watching films from their beds....<br>
- <strong>simplify your life...</strong><br><br>
What is wonderful is that <strong>you only need to get one toktoktok box to start your toktoktok install</strong>.<br>
Power/lamp switching sockets can be bought <strong>in your country</strong> from various companies, and you can <strong>make the computer RF receiver yourself.</strong></p>
<p><a href="https://www.limpkin.fr/public/toktoktok/principle.png" title="Toktoktok principle"><img src="https://www.limpkin.fr/public/toktoktok/.principle_m.jpg" alt="Toktoktok principle" class="media-center" title="Toktoktok principle, mar. 2012"></a><br>
And now,<strong> let's get technical!</strong><br>
As you can see in the simplified view of the toktoktok box above, the system can be powered by either batteries or a power supply, has an<strong> audio processing circuit and a 434Mhz RF emitter</strong>.<br><br></p>
<h2>The audio part<br><br></h2>
<p><a href="https://www.limpkin.fr/public/toktoktok/contact_mic.JPG" title="Contact mic"><img src="https://www.limpkin.fr/public/toktoktok/.contact_mic_m.jpg" alt="Contact mic" class="media-center" title="Contact mic, mar. 2012"></a><br>
In this picture is shown a contact microphone, <strong>placed at the bottom of the toktoktok box</strong>.<br>
What is a contact mic? Well, it is just a fancy word for a<strong> piezoelectric element</strong>. It is very simple to produce, has a non linear response curve and a resonant frequency around 3kHz.<br>
Why is it well suited for this project? Because it will <strong>only 'listen to' the vibrations of the surface it is fixed to</strong>.<br>
Then you just need to amplify the signal coming out of the mike and you're good to go. However, special attention must be paid to the input impedance of the amplifying circuit, as <strong>the piezo's impedance is very high</strong> (ie: it can't produce a lot of energy).<br><br></p>
<h2>The RF part<br><br></h2>
<p><a href="https://www.limpkin.fr/public/toktoktok/PCB_RAW_Toktoktok.JPG" title="Toktoktok PCB"><img src="https://www.limpkin.fr/public/toktoktok/.PCB_RAW_Toktoktok_m.jpg" alt="Toktoktok PCB" class="media-center" title="Toktoktok PCB, mar. 2012"></a><br>
See the big PCB trace on the right? This is a <strong>loop antenna</strong>.<br>
A loop antenna is basically a piece of wire resonating at a given frequency. However, the <strong>very</strong> hard part is to adapt the length of this antenna to allow <strong>a maximum of power to be transmitted to it</strong> (otherwise it is reflected back to the transmitter).<br>
I'm not going to explain in details the different types of antennas that exist, <a href="https://www.limpkin.fr/public/toktoktok/Tutorial_Antennes.pdf">but here is a very good document that shows them all</a>.<br>
An ideal loop antenna should be a <strong>quarter of the chosen wavelength</strong> long. But it is possible to make it shorter by <strong>adding terminating capacitors</strong> (in the pF range).<br>
So how do you make a good loop antenna? You make <strong>different variations of your antenna design</strong>, choose the one that has the best performances, and again...<br>
Seems very professional right? Well, if you don't have a PhD in RF design <strong>everyone will tell you to do that</strong>...<br>
The tool that I used to measure my RF performance was the RF explorer:<br></p>
<p><a href="https://www.limpkin.fr/public/toktoktok/rf_explorer.jpg" title="RF explorer"><img src="https://www.limpkin.fr/public/toktoktok/rf_explorer.jpg" alt="RF explorer" class="media-center" title="RF explorer, mar. 2012"></a><br>
I have to say it is a wonderful tool, and very cheap: <strong>100$</strong>.<br>
Still, you'll have to spend <strong>several hours</strong> to get a nice result.<br><br></p>
<h2>The whole system<br><br></h2>
<p><a href="https://www.limpkin.fr/public/toktoktok/PCB_Toktoktok.JPG" title="Toktoktok PCB"><img src="https://www.limpkin.fr/public/toktoktok/.PCB_Toktoktok_m.jpg" alt="Toktoktok PCB" class="media-center" title="Toktoktok PCB, mar. 2012"></a><br>
For this project, I have chosen a <strong>RFPIC</strong> from Microchip.<br>
It is actually ideal for what I wanted to do: it has <strong>an ADC, a programmable voltage reference and a 434Mhz RF transmitter.</strong><br>
The ADC will allow me to have the audio data on which I'll run my algorithms while the voltage reference will be used to set <strong>different levels of vibration sensitivity</strong>. Perfect, right?<br>
One switch is present to let the user set the desired behavior of the toktoktok box, and a RGB led displays the system status.<br>
This toktoktok box has a <strong>2 years autonomy</strong> when powered by 2 AA batteries, which is not that bad knowing that you must have <strong>at all times the audio circuit powered</strong>.<br>
Don't forget that a tradeoff must be made between product cost and autonomy ;-) , with this solution, I have a relatively low component count! <br><br></p>
<h2>The RF power sockets & remote control<br><br></h2>
<p><a href="https://www.limpkin.fr/public/toktoktok/rf_plugs.JPG" title="RF plugs"><img src="https://www.limpkin.fr/public/toktoktok/.rf_plugs_m.jpg" alt="RF controlled sockets" class="media-center" title="RF plugs, mar. 2012"></a><br>
I'm sure that you have already seen these RF controlled power sockets... and you'd be surprised to know that they all use the same kind of RF communication: <strong>434Mhz ASK</strong>.<br>
With an oscilloscope connected to the remote control, reverse engineering the thing is done in several minutes ;-) .<br>
And bam, <strong>the toktoktok box is interfaced to these plugs</strong>.<br>
FYI, <strong>my antenna design has a better performance than the remote control shown in the picture</strong>. Epic win!<br><br></p>
<h2>The RF toktoktok computer receiver<br><br></h2>
<p><a href="https://www.limpkin.fr/public/toktoktok/toktoktok_receiver.JPG" title="Toktoktok computer receiver"><img src="https://www.limpkin.fr/public/toktoktok/.toktoktok_receiver_m.jpg" alt="Toktoktok computer receiver" class="media-center" title="Toktoktok computer receiver, mar. 2012"></a><br>
This is <strong>the fastest mini project I have ever made</strong>.<br>
A 16$ teensy, a 5$ RF receiver from sparkfun, 3 solders <strong>and you have a toktoktok interface for your computer</strong>.<br>
You can then do <strong>plenty of things</strong>, from emulating keyboard presses to doing some more advanced processing if you chose to change the RF toktoktok protocol.<br><br></p>
<h2>Cool! So what now? Where are the files?<br><br></h2>
<p>You can already pre-order some toktoktok boxes if you want to play with them in the future :-) .<br>
<strong>All the production files, BoM, source code will be released under a TAPR Open Hardware license if the indiegogo campaign is sucessfull</strong>. Raspberry is doing more or less the same, right ;-) ?<br>
You are several thousands watching my blog every month, I'm sure some of you can help me :-) .<br><br></p>
<h2>Don't forget the logo design contest!<br><br></h2>
<p><a href="https://www.limpkin.fr/public/toktoktok/what_logo.JPG" title="which logo?"><img src="https://www.limpkin.fr/public/toktoktok/.what_logo_m.jpg" alt="which logo?" class="media-center" title="which logo?, mar. 2012"></a><br>
Here is the thing:<strong> I don't have a logo to put on the toktoktok box</strong>.<br>
Therefore, I have decided <strong>to let people contributing to this project to propose their design</strong>.<br>
That's right...<strong> I will not have a say in the chosen toktoktok logo!</strong><br>
And don't worry... the final toktoktok finish quality will not be the same as the one shown in the picture ;-) , final boxes <strong>will have a nice smooth abs aspect</strong>!<br><br></p>
<h2>The future of toktoktok?!<br><br></h2>
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<p>In case the project encounters a huge success, I'm already working <strong>on the version 2 of the toktoktok boxes.</strong><br>
They will have bidirectionnal RF communication and much more processing power to run advanced algorithms ;-) .</p>