This is an enclosure for a cheap type of mini pump, making it compatible with the pneumatic program of the fischertechnik construction toy system. As the pump needs 3V as input, a small step-down converter is included in the design, so that the usual fischertechnik 9V (or anything between 6V and 23V) can be used.
In my tests, the pump provided up to ca. .7 bar at ca. 3.5V input. Due to its size it's quite slow, though, and not adequate for heavy-duty applications.
Apart from the enclosure you'll need:
- Mini air pump e.g. from ebay. You can find them by searching for Transparent Mini Air Pump and comparing the results with my pictures.
- Step-down converter. Find this by searching for Mini DC-DC Converter Step Down Module Adjustable. Watch out, there are several similar looking designs, you want to look for the smallest type with "DSN-Mini 360" on its backside.
- 1A Schottky diode, if you want to protect the converter against reversed polarity (highly recommended). I used a BYS21-45 diode, that I had lying around. I'm sure there are better types, but I'm no expert on this, so if you have a better recommendation, please leave a comment.
- 4mm brass rod, 2.4mm high quality metal drill, and drilling aid from my N20 mini power motor design for the two connectors (see there in the Post Printing section for instructions).
- Soldering iron and short pieces of wire.
- Super glue to seal the enclosure permanently.
Related thread at the Fischertechnik forum: https://forum.ftcommunity.de/viewtopic.php?f=15&t=4821
I print at .1mm, but .2 should be fine
- See my N20 mini power motor design for instructions on how to make the two brass connectors (scroll down to Post Printing).
- Adjust output voltage of step-down-converter to 3V (or a slightly higher voltage for more power, I used ca. 3,5V) and connect its outputs to the motor, polarity is indifferent. Be aware that the step down converter will eat up 1.5V and the Schottky diode an extra ca. .5V, so that your input will need to be at least 2V higher than the output voltage you are choosing.
- Connect the brass connectors to the step-down converter according to the polarity indicated on the enclosure.
- If used, insert the Schottky diode between the negative brass connector (the published design has some extra space at it's side; the pictures show an earlier version, where I squeezed the diode in between the converter and the motor) and the negative input of the converter. The diode's negative (marked with a line) should connect to the brass connector.
- It's a tight fit, so don't make any wires in the above connections longer than necessary.
- The lid should remain closed on its own, use some super glue to be on the safe side.