Arduino OpenTherm Monitor Shield

Yesterday Freddy Martens contacted me. His name rang a bell, because I had seen his name before.. yep,  he is/has also been working on the Pale Blue Dot Opentherm Monitor as can be seen in the comments at the bottom of the page. He sent me an email and told me that  he had some Eagle designs for an Arduino Shield for the OpenTherm Monitor. His design is based on the schematic he found on the Pale Blue Dot site which I mentioned before – here and in earlier posts. And he asked me if I could host his Eagle files. Sure!

Arduino OpenTherm Monitor Shield


The archive contains both a single-layer and a 2-layer design. He also told me that the designs are not perfect – for example, some of the pads are too small. But this could be a good starting point for others. So if you’re interested, just download the OpenTherm4Arduino archive.

Freddy also provided some images he made of his Arduino OpenTherm Monitor shield, which can be seen here.

Have fun!

Current status on my own OpenTherm Monitor project is that I’m getting lots of decoding errors- but I’m not giving up yet!


Bedroom lighting almost finished

A small update with some results on the bedroom floor lighting project.

Bedroom floor lighting

The small red dot in the center of the image above is where the hardware is (the boxed Arduino) with the PIR to the left. It’s hard to make a picture in almost complete darkness – keeping the picture sharp but also getting a result with colors that match with what my own eyes see is not that easy.. But the picture above resembles what I see when I get out of bed during the night well enough – and it’s exactly what I wanted! The LED strips (1.5 meters on both sides of the bed) light up the floor well enough to spot any obstacles, but it doesn’t light up the whole room. And the 15 seconds turn out to be the right amount of time to light up the floor; and the LDR  takes care of unnecessary lighting during daytime; so in one word, the only conclusion can be: perfect! 

One small glitch though, which points out the difference between a clean testing environment and usage in real life: some days ago, when I had to change the alarm clock, I switched on the bedside lamp so I could see the buttons on the alarm clock. This triggered the LED strips to go on!

This means that the switching of the 230V lamp resulted in a ‘spike’ on the PIR sensor input on the Arduino… hmm. I think I’ll have to redo some wiring and use shielded cables instead of the unshielded & untwisted ones I’m using right now. My bad…

Perhaps another solution would be to watch the incoming PIR signal on the Arduino more closely and detect whether it’s a short ‘spike’ or not and decide not to turn on the LEDs on a short ‘high’; but that just doesn’t feel right – cables first!

No more painful toes

This evening I wrote a sketch to protect my toes better. The sketch switches the LED strip on and off based on motion detection by 2 PIRs. It works 😉

The blue LED on the Protoshield indicates when there is motion detected by the PIR. The motion detection turns the LED strip on and it will stay on until a period of 15 seconds with no motion has passed – only then, the LED strip is turned off again.

The sketch takes care of the “soft on/off” feature, by gently raising or lowering the brightness during a configurable time-span.

All that’s left to do is cleaning up the code, solder some wires, wait for the enclosure to arrive and give the LED strip, PIRs and Arduino enclosure a place under the bed.

Simple, yet very convenient automation 🙂

Bedroom floor lighting

Last week I had some trouble getting out of bed during the night without hurting myself. So this evening I decided to do something about that; I need something that can light the floor while someone is walking through the bedroom at night. So I made a list of things with which I could make something useful for that:

  • An Arduino Duemilanove;
  • a Protoshield;
  • 2 PIR motion sensors;
  • a LDR;
  • a  IRLZ34N MOSFET to drive the LED strip;
  • a 12V power adapter;
  • about 2 m. of white LED strip;
  • 2 LEDs (one for power and the other for motion detection);
  • an Arduino enclosure.


Automatic Bed light for the night

There it is… our automatic bedroom floor lighting is being tested at this moment. The 2 PIR motion sensors will be mounted under the bed in a way that they will only be able to detect motion caused by moving legs, the LDR will be used to detect whether it’s dark in the bedroom or not and the white LED strips will be glued to the bottom side of the bed and will light the floor when motion is detected.

The fun thing is that this floor lighting is almost completely built from spare parts (except the enclosure). The 2 PIR motion sensors were the first motion sensors I ever bought, but the lenses were too big for my taste to actually use them. Under the bed the size of those lenses doesn’t matter. The Duemilanove is one of the many Duemilanoves I have laying around for testing/experimenting, so I can easily do with one less – I could also have picked an RBBB, Teensy or JeeNode. The number of unused protoshields made me decide for an Arduino. And all the other parts were all purchased in the past with the thought they’d be handy to have around for when you suddenly need them 😉

No RF, Zigbee or Ethernet this time – this will be a solution that doesn’t need any other external input, nor do I think I’ll use the fact that someone’s walking through the bedroom in the rest of my system. Nevertheless, I’ll reserve some space on the Protoshield for a XBee Breakout board cause this would actually be a very good place for a Zigbee router on the 2nd floor!

The sketch will be a collection of code  from other sketches I’m already using, so I hope that at the end of this week I can finish this and never hurt my toes again 😉

Building the sensor hub

The basic ideaBecause I’m working on 4 different things simultaneously, all 4 of them are not progressing as fast as they could. And this new sensor hub is not top priority, so sometimes it takes a while before I can spend some time on it. The last few days I came up with some basic idea; this is what I have in mind for my sensor hub.

The lower side of the enclosure will have all the connectors for power and other wires to the sensors and the upper side is where a small 5V power adapter with USB connector (of which I bought a couple recently, for only 5 euro/piece) and cable will provide the necessary ‘juice’ to the Arduino Fio.

The FTDI breakout on the left is just for uploading sketches (and for power, while it’s still here on my desk).

Inside the enclosure there’s a half-size (400 points) breadboard with double-sided tape that will hold the Fio and the required wiring. Cheap and simple; and since this setup will take care of 4 of my all-in-one sensors, I can live with the fact that it’s not battery powered. This certainly doesn’t mean I’ll never build battery powered sensors anymore…

First sensor finished and working

Power wiresToday I finished soldering a cable to my first new All-in-one sensor with motion, temperature and light. Phew, after soldering those 7 wires my eyes really needed a break, even though I used a magnifying glass. The very first thing I did was getting rid of the headers for the H/L jumper; I reduced the 2headers I needed to 1 mm and added a drop of solder in between; the unused header was cut away completely. This gave me some more free space  for the black wire which connects the GND pin of the PIR to pin 1 (GND) of the DS18B20. After that I connected DS18B20 pin 3 (Vdd) and one leg of the LDR to each other so that I only needed 1 wire for supplying both sensors with power by connecting those to the + pin of the PIR; this is the red wire.

Now all the sensors were connected with each other in a way that when I would apply power to the PIR pins, the rest of the sensors would be powered as well.

Connecting the cable

As you can see a CAT5 cable was used; I only needed a total of 5 wires for this sensor. First I needed a way to glue the cable to the top cover of the enclosure; I saw there was some space between the PIR PCB and the top cover, so I what I did was remove the outer isolation on one half of the cable but left the other half intact. I added a drop of hot glue to it and quickly pushed it between the PCB and top cover, which made the cable isolation work like some sort of pull relief. Soldering the 5 wires was the last thing I did; cause now it was time to check some things first – does it work??

I wrote a small sketch that would read all the sensors once a second and display the results (do I hear a drum roll? ;-):

10765455 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=643
10766546 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=640
10767638 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=640
10768730 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=645
10769821 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=653
10770913 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=657
10772004 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=663
10773096 Motion:no,  Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=661
10774188 Motion:YES, Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=666
10775279 Motion:YES, Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=668
10776371 Motion:YES, Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=663
10777462 Motion:YES, Addr:28-98-C9-AF-2-0-0-A3 Temp=25.25 grC, LDR=660

It works! Maybe I’ll put some drops of hot glue here and there to make it all slightly firmer and than I can close this sensor.

The sketch is still very basic; it’s just some Serial.prints you see here, no wireless transmission is done yet and there’s an ugly delay(1000) in the loop() for the 1-Wire delay that I have to get rid of.

And I don’t need temperature and light sent to me every second; but waiting one second before motion is detected is way too long of course. Using interrupts for detecting motion is better I guess… soon I’ll know more about that, cause I need to be able to handle 4 PIRs (on 4 different input pins), but I can’t have 4 ISRs (Interrupt Service Routines); but the ‘solution’ will probably suffice. Sounds like a nice subject for another post.

Success and failure

Today I continued with my “RGB LEDs for the gazebo” job; what would those 6 LED spotlights bring, in terms of light? How would it look? Well, here some images:













I wanted to see the result before I would start digging holes, laying cables under the pavement etcetera. Based on what I saw after sunset, the conclusion can only be: we have a Go! It’s exactly what I had in mind; which is a big relief actually, cause those 6 LED spotlights were quite an investment. But the result is wonderful, these LED spotlights light up the gazebo just the way I want.

I did have a big issue with controlling those LEDs though.. All the tests I did in my office with the LEDs on the desk next to me never failed. But today, with the LEDs, DMX decoder, Arduino+Ethernet shield+DMX shield outside it didn’t work anymore!? Everything was set up and ready to go, but I couldn’t even ping my Arduino anymore!

My first thought was that the new CAT5 cable of 20m length was broken, or the RJ45 connectors didn’t make good contact; but this was not the case, the cable was OK. Maybe it was the new Gigabit switch I received 2 days ago which hadn’t been used until now? Nope. What is this??

I took the Arduino back to the office, connected it to my PC for power and to the switch. And it worked again, just like it always did… although I did see the LEDs on the Ethernet Shield behave differently. Well, I won’t go into all the details, but eventually I found out that it was the USB connection that made the difference! Without a USB connection, I had to push the reset button on the Ethernet shield to make the shield work. With USB, the Ethernet shield worked immediately. Go figure..

What has USB got to do with a (dis)functioning Ethernet shield?? A lot, so it seems. What is this, a hidden feature? By design? I must have missed the addendum to the manual that says “This shield will only function with your Arduino USB port connected”… After I knew what was causing this problem, it didn’t take long before I found a solution – phew, this issue could have been a real party pooper! I haven’t tried the workaround yet, but I will. Very soon, as in tomorrow first thing!

Here you see me testing some colors, sitting behind my laptop under the gazebo:


Arduino DMX encoder on the test bench

Today I started testing my DMX project. The ingredients:

  • Arduino Duemilanove with Ethernet shield and DMX shield;
  • DMX decoder PX24500;
  • 24V PSU;
  • 6 x Artecta RGB LED;
  • some wires;
  • a sketch running on the Arduino;
  • UTP cable;
  • software tools.

After connecting all the wires, switching on the PSU, starting the Arduino and checking if the Arduino was succesfully connected to my LAN by pinging it, I was ready. I opened the Arduino IDE Serial Monitor so I could see what my sketch was doing and sent a “command” to the Arduino. For that I used wget, a non-interactive network retriever; most people who know Unix-like OS-es will probably know about its existence but it’s less known among the Windows folks. Well, in just a few words it’s a tool with which you can store the results of a HTTP call into a file and do all kinds of other handy stuff .

I started carefully; the first command sent to the Arduino was:


What this should do is change the R-value from its current value to 10 in 0.5 (5*0.1) seconds. G and B values are set to 0 immediately.

What the  Arduino webserver will receive is the following:

 GET /10,0,0,5,0,0 HTTP 1.1

 ....etc, the rest is all standard HTTP headers

After parsing the request and figuring out what to do, the Arduino starts changing the LED colour by issuing DmxSimple commands according to the values received in the HTTP call.

Ok, the moment of truth is here… will the LEDs start producing light or not? Yeah, they did! Tadaa…

This is not Red (nor is it a pipe)

The moment I saw this working, I felt the need for a more sophisticated way to control the RGB values, so I wrote a small tool in Delphi to help me pick the right color:


With a mouse click I can now select the color; the rest is done automatically: calculating the R-, G- and B-value and performing the HTTP call. And all it took was 10 lines of code (with the help of Indy and a very nice Color Lib made by Marco Binic). This allows me to choose a color much quicker and more precise than by editing numeric values on a command line 😉

I did find some issues during my first DMX adventure, so I haven’t reached the phase yet where I can start digging holes in the ground; I’m not totally satisfied yet – more on those issues later, when I’ve hopefully fixed them.


Stacked stock

Stacked shieldsHere you see an Arduino Duemilanove, an Ethernet shield and a DMX shield. Well to be honest, the top shield is 1 day old; the rest has been on the shelf for more than a year. I wanted to start using some of the stuff I bought in the past but never used, so with the need for a DMX encoder to control 6 RGB LED spotlights, I decided to do it this way.

It was a bit annoying that I had to deal with how the Arduino platform works with shields and that you have to find out whether you can stack more than 1 of them on top of the Arduino and not have pin conflicts between the shields you want to use; this can happen so it’s always good to have a look at the pins all the shields use and see if there are any conflicts. In my opinion, the JeeNode concept is much smarter and easier in this perspective – and documentation is much better too!

Now back on topic again… as I said, this combination of boards is going to be used as an Ethernet enabled DMX encoder with integrated web server. Sounds difficult? It’s not, actually…

The DMX shield (from the Arduino store, made by uses the DMXSimple library and indeed, it’s very simple. All the hard work is hidden and all you have to do is use 2 or 3 simple functions to get DMX encoding working.

The same goes for the Web server part; the Ethernet library makes it as simple as it possibly can.

So all I had to do was write some code to parse the values I wanted to send to this DMX encoder (R-, G- and B-values and some time values to soften color changes); and now I’m waiting for the LED spotlights to arrive, cause I’m ready for it! Yep, that’s the other side of the story; you can build cool stuff in a matter of minutes, add your own code for some extras and it works!