I designed a very simple power converter for the snow flake decoration. The snow flake boards require 3.3V, a voltage which is not commonly available in a household. Therefore the power converter takes 5V USB power and convert it into the required 3.3V.
There is no fancy circuit inside of this box, lazily I simple used a Traco Power TSR2-2433 DC/DC power converter. It is a single component containing everything required. No external components like capacitors or resistors needed.
Today I show you a little bit longer video about the assembly of the component side of the snow flake panel.
Compared with the very small 0402 LEDs (1mm x 0.5mm) on the front side, the component side contains just regular 0805 resistors and capacitors.
The first part of the video shows how I apply the solder paste using a metal stencil. I use a system called “eC-stencil-fix” from Eurocircuits. This is basically a set of plates with metal knobs to perfectly align the board with the stencil. With a tick in a checkbox, they produce panels which perfectly work using this stencil fix system, which is really convenient.
Here a quick video of the snow flake assembly. It shows the assembly of the LED side of the panel using hot air.
The assembly went without big problems, except there was a little bit excess solder on the pads. Therefore the LEDs do not lay perfectly flat on the board.
Eurocircuits delivered some perfect panels for the snow flake board. Each panel has five snow flake boards on it.
This was an impressive good job from from Eurocircuits. There are a quite number of challenges to produce panels in this outstanding quality:
Most vias are tented, which is very nice. These are 0.25mm diameter holes, so it is at the upper limit where tenting works.
I am very happy with the result! The people at Eurociruits have clearly demonstrated their skills and commitment to quality.
Now it will be a real challenge to assemble the board without leaving any marks on the white surface. 🙂
Recently, the boards for a small power converter arrived from PCBWay. This board house provides a fast and reliable service. In the following image you can get a own impression of the produced boards:
Today prototype boards from Eurocircuits arrived. The quality of this boards is outstanding. I do not know any other board house which delivers this incredible quality of boards. They really thrive for perfection.
Recently I finished a small cat feeding device. Meanwhile I added some minor missing parts, like an USB port which can be used to charge the device. I also added a larger battery to keep the device running for months without charging.
Here a short video demonstration of the project:
Read more about the project here
I finished a very simple and quick project recently. It is a programmable cat feeder device. The device is just made for one single portion, but it uses this slide which produces the distinctive sound if the pellets hit the bowl. It is no replacement for the usual feeding of the cat, but some flexible addition to give food out of the regular times.
The whole build was done in roughly four days, using a very quick prototyping and build method.
First I had to make a decision about the final size of the device. I used Autodesk Fusion360 to create a model of the device and try to fit all required parts into the device.
This is one of the last designs I made until I had the right size. I used a different mechanism as shown here, the important part was to get the right size.
Next I bought plywood in the right sizes for the outer shell of the case. I also got some additional panels fitting inside of the shell for the internal structure.
I created the shell with four sides, left the top and front side open. To work quickly I fastened the panels with hot glue in place. This has the benefit that you can remove panels using a hot air gun in the prototyping stage.
There was a long delay with no update about my projects. The reason for this is, I focused on other non electronic related projects. I promised to publish all files and information about the plant watering sensor project in August, and here are all the files.
Even with these files, it is a very advanced project to do. To produce the PCB, you need a board house which is used to precise and high quality PCBs, like Eurocircuits. Also all pads are prepared to reflow soldering, and not hand soldering. It may be possible to solder the resistors in place using a regular solder iron, but it will be hard to do.
This is the sixth part of the meta-tutorial, where I talk about designing a cheap plant watering sensor. If you did not already read the first, second, third, fourth and fifth part please do it now. These parts contain a lot information which lead to this point of the tutorial.
The fifth part ended with step 24, where I talked about calculating the total bill of materials. This part will focus on preproduction of a small batch of sensors to solve some final details.
Just note, I obviously do not follow these steps in a perfect sequential way. Often I start with some tasks earlier and things are running in parallel. There are various dependencies and it would make no sense to wait with some task just to follow a strict sequence. 🙂
If you follow my blog you may already read some details about ongoing tasks. I will just briefly talk about them in this article. You will find more details in the other blog posts.
Everything looks very promising, so its time to build a small batch of the final devices to see if they work as expected. This is also a test to see how a larger number of these devices can be produced and what kind of tools are needed for this task.
First I order the components. This is very important, because the availability of electronic components changes all the time. It is nice to have all required components, so you can order the boards with the correct footprints. If you order the boards first and are unlucky, an important component is suddenly unavailable and you have lots of boards with wrong component footprints on it.
The components for the plant sensor are really cheap, so there is no huge risk. Even it turns out a huge issue requires a component change – it will be a small loss. SMD components also do not take a lot of space, I can easily store all of them in a very small box. Continue Reading
