Doorgaan naar hoofdcontent

Posts

Posts uit april, 2018 weergeven

Fixed voltage on cheap buck converter (MP1584) conversion with single 0805 resistor

Everywhere I look on the Ali and Ebays I see these step down converters based on MP1584. I bought a couple and actually they are not bad at all.

The output voltage is set by the trimming-resistor in the left top corner of the picture. This works OK, but.. it is dangerous because it is rather sensitive to the touch.
I decided that I wanted fixed output, so I had to figure out how this thing worked. The datasheet looks like this :
R1 in the datasheet is what I call "R feedback" in my image. The value of R2 is mostly 8.2K Ohm in the boards I have seen. 


So to set some common values for output voltage:
change R1 to 27K for 3V3 output (actually 3.4 volt, but 27K is a standard value)
or
change R1 to 43K0 for 5.0 Volt output. (43 K is a standard value)
A standard 0805 size resistor fits precisely, how convenient ;-).

Make sure the other resistor is really 8.2K because that determines the feedback ratio.

This way you can not burn up your circuits by accident (or some funny clown tu…

Roman playing sword with my maker-girl

My girl has a classical Roman name "Diana" and with school visited the German city of Xanten. Xanten was a Roman settlement for about 400 years, starting about 15 years BC.
She bought a wooden sword (inspired by the Roman Gladius sword).
We decided to make it more realistic, I call that some good quality time with my girl.

I had seen this youtube video some time ago by Adam Savage.

And what he can do, we can do too we decided ;-) We gathered the materials, the aluminium tape and the 'fake' leather.  Grandmother had some stuff in stock.

We covered the 'blade' (in Dutch 'Kling van het zwaard' of ook wel 'lemmet' of 'blad' genoemd)
with the thin metal foil that is sold for repairing ducts, it costs about 2 euro for 5 meters and it looks very realistic. After we carefully applied it, make sure you do not stick it to itself ;-)  We used some scotch-bright (Dutch : keuken schuursponsje) to dull the glare, it was very shiny.


We found some &#…