Boost Converter

After watching a couple of YouTube videos about buck, boost converters and switching mode power supplies, I decided to take a closer look at this Arduino based approach:

http://playground.arduino.cc/Main/RegulatedPositiveVoltageBooster

I just had to find an inductor to start with. Desoldering inductors and capacitors from an old power supply left me with more than enough material to start playing.

For those interested in the details of my setup, here is a Fritzing of my breadboard. This is more or less following the schematic that can be found under the URL mentioned above.

The source code of the sketch I used and the Fritzing drawing can be found here:

https://github.com/fredvj/Arduino/tree/master/Boost-Converter

The three LEDs will indicate the status of the output voltage:

Green: Specified output voltage reached.
Yellow: Minor changes of the PWM duty cycle are required.
Red: Significant change of the duty cycle required.

When starting, the red LED will be on. If the desired output voltage can be reached, you should see the yellow LED within a second. Do not expect the green LED to be on all the time. Yellow will show whenever there are changes being made to the value of the duty cycle. It will depend on your ripple voltage if you just get the green or a mixture of the green and yellow status LED.

For low current loads (LED in my case) I have been able to triple or even quadruple the input voltage (5V -> 20V). The limiting factor is probably the PWM frequency of the Arduino. The sketch is setting the pre-scaler for a PWM frequency of 62500 Hz. Commercial integrated circuits will run at higher frequencies, but this is the maximum we can reach with an Arduino.

Kossel Mini Z-Probe Holder

Let me start by saying that the Think3DPrint3D Kossel Mini Kit is really fantastic. The documentation is pretty good and it took just three long evenings to get me to my first print. I first expected to finish the kit much quicker, but I have to admit that I underestimated a couple of tasks that are not that obvious before you start - including preparation of the printed parts.

The one thing that almost prevented a successful build was a lack of concentration on my side combined with a couple of photos that are hiding one critical detail of the Z-probe holder. The documentation is telling you to "clear out the groove" and this is what I did.

As you can clearly tell from the STL file: I accidentally cleared out the section that is needed for the retraction of the Z-probe to work.

All this left me with a printer that did not print and I had two options: Either ask someone to print a replacement part for me or come up with some kind of quick fix.I finally resulted to using an old CD to create a part that can be placed between the micro switch and the original holder.

Once I installed this quick and dirty fix and I got the printer ready to print I wanted to replace the holder. For obvious reasons I did not quite like the original part. After a couple of iterations this is what I came up with.

https://github.com/fredvj/Kossel-Mini/blob/master/Z-Probe/Z-Probe-holder.stl
 

Not only does it give you a clearer indication of what the groove is and what not. The placement of the spring will prevent it from blocking the probe when you want to release it.

If you do have a M2.5 x 6 socket cap-screw you probably want to replace the 12 mm screw used on the original part to fix the spring.If not - the longer one will work just fine.