This is the second part of the meta-tutorial, where I talk about designing a cheap plant watering sensor. If you did not already read the first part, please do it now. It contains a lot information about constraints and decisions made which lead to this point.
The first part ended with step 11, building a working prototype with the selected key components. So let us start with the next steps in this journey.
Step 12: Analyse and Measure the Prototype
Never forget why you actually built a prototype. It is your tool to verify all assumptions you made in the design phase. To do this you need the right measuring instruments.
The Power Usage
I start measuring the current of the circuit. This will show if my assumptions about the battery life will be true. For this test I use a multimeter which has a good resolution measuring in the µA range. The multimeter I use is the Testo 760-3 which is not a very well known brand. Multimeters are usually really poor at measuring low currents on low voltages, so let us see if this will work.
I also use a Fluke 114, but this one has no current measurement. It is sometimes very handy to have two multimeters, one to measure the voltage and a second one to measure the current.
For the first test I program the MCU to do all the tests in a loop and connect the power directly to the second part of the circuit. Now the power is always on and I can measure the current used by the MCU while doing the measurement.
I just finished a small series of the PissOff project. After all work done, I probably would use a stencil and solder paste next time.
For this series I used a slightly larger speaker to improve the loudness and sound quality. Tried some different ones, but the really good ones do not fit on the back of the project anymore.
While soldering all these boards, I found out the contacts of the SD card holder do not always easily connect to the PCB. If the SD card is not working, resoldering these solved problems for two boards. Also in one case, flux came into the trimmer, there was no contact anymore and no sound output.
I just published the guide for the five light spheres project. It is the perfect decoration for this Winter. The spheres always display a nice color combination and blend from one color to the next. It is a quiet and artful decoration.
Recently I had the problem some expensive components did overheat in my server rack. The ventilation was not optimal and I had to install additional fans. Because this rack is in my office and I like a quiet working place, the ventilation had to be as quiet as possible.
First I thought about buying a off-the-shelf product, but then I realised: If this controller does not work as I expect and the fans will spin too fast/loud, this will drive me crazy over time. So I decided to build a own fan controller. A very simple one, where I can write own code and tweak it until it runs as I like.
On the project page I describe how to build this particular controller. It is not meant you really reproduce this same controller exactly as shown, but maybe understand some basic principles to build your own controller.
I just finished part 2 of the project description for the Outmoded Sequencer. In this second part I describe the steps from the prototype to the final device. I copied the preface from the page after this link .
Building the Outmoded Sequencer was a really interesting project where I learned a lot. It was the first project with a custom designed PCB. Usually I just solder everything onto stripe boards, because I only produce one single device. The complexity of this device with the matrix forced me to design a proper PCB, soldering everything on a stripe board is feasible but requires more space and a different approach for the matrix.
Not everything turned out as well as expected. First there was the idea with the matrix using steel balls as switches: Even with the magnets generating a certain force to the pads, the steel balls do not connect as reliable as I would like they do. As you can see in the demonstration video, it is still possible to have a lot of fun playing with the sequencer – however better connections would make the experience even better.
Should you build your work Outmoded Sequencer? Yes, absolutely! But you should definitely use a different approach for the matrix. Best first only experiment with the matrix part until you have a working solution there before you add the other parts around.
Should you use the provided PCBs? No, better design your own board especially implement the matrix in a different way.
Should you use the circuit design as provided? Yes, definitely! The design is, in my opinion, a very good start and should give you a reliable and working device with minimal effort. Keep in mind: This is a minimal design and there and many ways how to improve certain aspects of the circuit. So feel free to address the problems if you have components left, to spend on this project.
Hurray! I just finished the final Outmoded Sequencer device. The tuning of all frequencies was way faster than I expected, because I used a new method. Have a look at the following photo gallery before I tell you some details.
You can see the device is build like a control desk, with the PCB a little bit at an angle. The left knob on the top controls the speed of the sequencer and the right one the volume.
A did a few tests already and the idea with the steel balls is working, but not great – just ok. So sometimes they do not connect and you have to move them a little bit until they make contact again. Most of the positions are working always without problems.
It is a great fun to play with the device, changing the pattern while the melody is playing. Now everything is finished, I also can move two steel balls at a time which can create interesting variations.
Next I will do a detailed video, where I demonstrate the final Outmoded Sequencer. It should give you a better impression of the device in action. I will also setup a complete filter chain, so you can experience how easy you can use the sound of the sequencer as input to do various interesting effects.
I will also add the second part of the project page, where I explain some of the details about the magnet matrix and how the whole thing is built.
There are seven absolutely perfect PCBs left, so I think about to give them away if someone is interested into building the project. But be aware, this is no kit, just the plain PCB. You also have to use the exact same components as I did – or at least ones which perfectly fit into the holes. All components should be available to buy at various stores, and I will provide the exact part numbers.
Here a short update on the progress with the final Outmoded Sequencer project. I did the whole assembly of the final PCB and connected everything. You can see part of the soldering process in the following video:
I accidentally cut a route on the bottom of the PCB, so I had to fix this with a short wire. It is not visible on the final device. The magnet matrix mentioned in a previous post is already securely fastened to the bottom and holds the steel balls in place.
There are only the final adjustments of the frequencies left to do. I have to tune each tone and add the last four missing resistors.
Today beautiful violet PCBs for the Outmoded Sequencer project arrived. I use them to experiment with different approaches for the matrix. The PCBs are ordered from OSH Park, which is a community printed circuit board order service. They put PCBs from multiple parties on one large PCB, which makes everything cheaper.
I just started an interesting new project: The Outmoded Sequencer Project. It is an minimalistic music machine. You can use a 8×8 “programming” matrix to create simple melodies which are looping endlessly. This melody can be changed while the device is playing it. Here a short demonstration:
The device is divided into several parts as shown here:
My goals for the project were:
Only outmoded, basic and cheap components.
As minimalistic as possible.
Maximize the fun with these limitations.
Read all details how you can build this sequencer on the project page: