Crowded or not?

An often heard remark in the domotica scene is that the 433 Mhz frequency used by european devices is to crowded and will give you a bad performance. I also notice that this dogma is often repeated by others without asking themself is the ture? While yes, many devices work at this frequency but not all at the same time. You also have to consider that this isn't a fixed frequency they use but it's a range devided into channels so two or more transmitters can broadcast at the same time.
Test hardware Now let's see how busy it realy is on this frequency by using some high tech tools that are available for just a few euro's. This is the receiver i used. Together with some very smart software it can be turned into a receiver that can operate from about 210 Mhz up to 2.1 Ghz. How about that for just 25,- euro's!
The test equipment i used is a terratec cinergy dvb-t usb stick and SDRSharp as software. Just google on these words and you will get loads of information to get you started.
Frequency This is an overview of the frequency in tuned into. It's the frequency of the RFXCom transmitter used in my domotica system. The red line in the middle is the transmitters frequency and the line next to it is just the cursor showing the details of the location it is pointing at. Now we are listening at the frequency range from 433-435 Mhz. Waterfall If we let this run for a while a so called waterfall image will appear showing all the detections over a time period. The vertical axe is the time axe with the newest information on the top and horizontal the same frequency range of 433-435Mhz. The displayed information is for about 25 seconds. At the bottom you see a transmission of RFXCom and the horizontal line in the middle is caused by a transitting motion detector. As you can see there are no other transmissions in those 25 secs. When i let it run over a longer period of time this hardly increases. So now you know all about how crowded the 433 Mhz band is at first hand.


  • By: A.A. van Zoelen
  • On: 11/11/2012


Autumn We are preparing us for the coming winter but first there is autumn with its rain, wind and falling leaves everywhere. While pruning some trees i had some twigs left over and a load of beautiful colored leafs. I twisted the twigs into a nicely round shaped wreath and decorated it with the leaves. Patiently glueing the leave with hot glue to the twigs. I added some grass from the garden for a nice touch and look and behold the result.
I am ready for wintertime.


  • By: A.A. van Zoelen
  • On: 04/11/2012

Washing machine ready

Washing machine ready notification Another idea born out of fustration. Our washing machine and tumble dryer are on the first floor and when loaded with a new batch it takes an hour or so to finish. However we never knew for sure when it was finished. As a result of several walks upstairs just to find out that they wheren't finished yet this idea was born.
This needs to be improved.
I had a nice circuit from this site ( and i gave it a try. Although it worked at first it had some minor issues. Using two DS10 transmitters didn't work very reliable for me. Also each unit consumed two AA batteries and another 9V block for the circuit didn't do good for me either.
So what did i change?
I took a MS13 motion detector and i removed the cover and i trimmed the sides so it would fit into the enclosure. I also removed the LDR and the PIR sensor from it. Since the LM324 chips can be powered at 3V i hooked this one also to the battery of the MS13 motion detector. The lm324 chips is a low power design so this won't drain the batterij so much. The outputs from the circuits that first where going to the DS10's are now connected to the data pin of the PIR sensor and the hot side of where the LDR was located.
Till now there where no false detections. Time will tell.
Please note that this MS10 is one from the US and it was working at 310 Mhz and is refactored to work at 433 Mhz as seen on the image


  • By: A.A. van Zoelen
  • On: 03/11/2012


Battery dispenser This idea is the result of someone being annoyed about something.Every time when i need some batteries for an experiment or a sensor i had to grabble for them in a large box.There had to be a better solution for this and there is. The battery dispenser. Not only are they nicely sorted, you can also see when a specific battey type runs out of stock.


  • By: A.A. van Zoelen
  • On: 27/10/2012


Z-Dyne Shortwave tube radio Finaly! Finaly i finished my longest project ever. Normaly i only do projects that last about 1 to 2 months otherwise it becomes a drag and then i am loosing intrest in it. This one took me more then a year to complete so this is a personal victory in more than one way.
Klik here for more details


  • By: A.A. van Zoelen
  • On: 14/10/2012

Monster bike

Monster bike On Sunday there was a big celebration in the small village i live with lots of food, drinks, music and a market with all kinds of goods. There where also a few attraction and one of them was riding this bike.


  • By: A.A. van Zoelen
  • On: 09/09/2012

Going to church

Going to church This weekend i had the change to visit the church and more specific the bell tower. On my way up i passed the space between ceiling and the roof of the main area of the church. I had a good look at the construction and wondered how it was made.


  • By: A.A. van Zoelen
  • On: 09/09/2012

Bio diesel

Bio diesel After cleaning the frying pan again i was left with 3 litres of heavily used sunflower oil. Normaly i dispose this by dumping it next to the other garbage but this time i have other plans, making biodiesel!
The chemistry involved in this is to dissolve some lye in denatured alcohol (or methylated spirits ) After the lye is dissolve you pour it into the oil and shake it for about a minute. The oil should be around 60 degrees Celsius for an optimum reaction. For this I just placed the bottle in the sun on a hot metal plate. The eco-friendly way. After an hour or so you see that the bio diesel is floating on top of the residue that is left over. The bottle in the middle is already filled with bio diesel and if you look well you see a darker area at the bottom this is still pollution of the biodiesel.
For me this is enough because i will use this as fuel to light the woodstove in the winter. If you actually want to use this in a diesel engine then you have to wash this to purify it more before it is usable in an engine.


  • By: A.A. van Zoelen
  • On: 08/09/2012

Swallow again

Swallow again There are eight swalow's claynests attached to my roof and each nest had two or three young birds. The swallows have their second nest this season so you can imagion that it is crowded in the sky. The parents and the young birds from the first nest are roaring the sky in search for insects. The young birds in the nest keep a good eye on their parents actions. This one even wanted to take part in it but wasn't able to fly yet and felt on the ground. In just a few days he will be strong enough to join the flock and travel South to Egypte. [update: he joined the flock]


  • By: A.A. van Zoelen
  • On: 06/09/2012

Home grown food

Home grown food Weather was nice and i had a walk in my garden. While wandering around i pick ripe fruit and vegetables that seems ready to harvest. Within moments i have enough vegetables for a few days. And a sugar melon and apples for dessert.
Life can be so good if you can enjoy simple things.


  • By: A.A. van Zoelen
  • On: 30/08/2012


Bookcase The attic has plenty floorspace but a sloping roof make it all rather inaccesible. However it is good enough for storage space. What i did here? I made a large bookcase. About 4 meters width and 1.7 meter high. This bookcase is a divider between the floor area that is suitable to walk on and the storage area behind it. To make the storage accessible i turned the bookcase into 2 large doors. One 1.5 meters and one 2.5 meters width. To carry the load and still open the doors smoothly i used 4 inline skate wheels, two for each door.


  • By: A.A. van Zoelen
  • On: 26/08/2012

Hanging tomato

Hanging basket with tomato plants Getting the most out of my garden during the summer is always my goal.
All the ground area is used so there is no more room for some extra tomato plants. How to proceed next? well, just take a few plastic containers and make sure that there is one or more one inch holes in the bottom. Make three holes in the rim in such way that you can later put wires through them and hangs the container as a basket. Fill the container with plant soil and press it in the container. Not to tight but tight enough to keep it in the container when you turn it upside down. The container is now filled with soil and bottom up on the ground. Place in each hole one or two tomato seeds and water it. Soon the seedlings will raise. When the young tomato plants have a few leaves or are about 10 inch tall take the container from the ground and turn them around again. Now the plants are hanging beneath the container. Put strings through the rim and hang the container in place. Watering is just a matter of pouring it on top of the soil. Now, the production of the plants will not be as high as if they where planted normally but that is always the case with tomatos in small containers. And you didn't had room for it anyway.


  • By: A.A. van Zoelen
  • On: 12/08/2012


Some soap pieces Making homemade soap.
While washing my hands i was wondering how soap is actualy made. They already make soap for ages but that knowledge seems to fade away by the common people. I started a search on the internet and to my surprise i found many, many sites about the subject. It turns out that soap is made from fat or oil and NaOH or commonly known as lye (in Dutch it's also know as 'gootsteen ontstopper'). Different oils give different types of soap. For example cocos oil will give you some foamy soap. The white soap here is just palm oil (Dutch: 'frituurvet'), the rose shaped soap is made from palm oil, olive oil and rose essence and for the pink with green blocks i used the same mixure but i've added some food coloring to get the green color.


  • By: A.A. van Zoelen
  • On: 10/08/2012


I made this picture of a really big dragonfly laying her eggs in my pond. Dragonfly laying eggs A few weeks later i noticed an other dragonfly hanging on a branch. She was changing here skin. Apparently she grown to big for it and had drop it of. The next few pictures will show the process of pumping up her wings and to dry up so everthing hardens enough for a safe flight.
Dragonfly pump up her wings
Dragonfly drying


  • By: A.A. van Zoelen
  • On: 25/07/2012


Insect If you take the time for it you will notice more and more beautiful creatures around you. You don't have to go to the tropics to see nice colors or shapes. You can even find them in your own backyard.


  • By: A.A. van Zoelen
  • On: 28/06/2012


Caterpillar While working in the garden i noticed this beautifull looking caterpillar.


  • By: A.A. van Zoelen
  • On:28/06/2012

Pond vacu

Pond vacu cleaner The pond needs cleaning from time to time and i've seen what seems to be a nice device to do the job. However it got also a hefty price tag on it. So first a visit to the shag to get some materials to make one my own and see if this thing is worth its money. I used some pvc pipe and an air gun that is used to pump up car tires. Combine this with an aircompressor and you have something what they call an airlift. Opening the valve a little and air will blow out at the end of the pipe which is near the bottom of the pond. The bubbles will rise in the tube and push water upwards while sucking in water and dirt from the bottom of the pond. Although it works reasonable i wasn't impressed with it's preformance so i dismantled everything again and started to clean the pond the old fashion way. Just scooping out the dirt by hand with a fishnet.


  • By: A.A. van Zoelen
  • On: 14/06/2012

Block with coils

Tube shortwave radio For about 6 months now i am working on a own design of a shortwave receiver with tubes. I have taken a few steep hurdles already and at the moment i am tackling the biggest one. The bandselector and the coils that come with it. This is a picture of one of the things i tried to get it working and indeed it will work but it isn't a nice solution when you are still experimenting a lot to get things right. This one is desoldered again.


  • By: A.A. van Zoelen
  • On: 10/06/2012

Solar dryer

Herbs dryer Last year i had a lot of herbs and tomatos from my garden that i couldn't process in a energy friendly way so i came up with this device to do the job. It's an old aluminium casing o which i added a wooden door. The lower part has a windowed compartment to collect the solar heat. Inside this area i place soda cans painted black for extra heat absortion. I made a hole in each can so hot air would rise up more easily. The design is rather flawed and isn't working as expected. It does a good job but only when the sun is shinning full at it. Anything less and the thermal losses will take the upperhand. Well i have learned some lessons with this and i will redesign this one again comming winter. .


  • By: A.A. van Zoelen
  • On: 1/06/2012


Opening a new year A new section has been opened to accommodate my activites in domotica. I created a few scripts for traffic monitoring. And with traffic monitoring i mean the traffic jams and the railroad delays. Both scripts are made for HomeSeer.
Get your copy here


  • By: A.A. van Zoelen
  • On: 16/01/2012

Opening a new year

With the new year already going for a few weeks it's time to do the annual swap of the archive. I opened a new page for this years activities.


  • By: A.A. van Zoelen
  • On: 14/01/2012
Postings in 2011