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Showing posts from January, 2020

Small 12V Buck PSU

How does one build reliable electronic circuits?  By starting with a reliable and clean power supply. The three terminal linear voltage regulators have been almost obsoleted by three terminal switching regulators.  It is now quite trivial to make a very efficient small power supply by using one of these modules - available from Mouser and Digikey. I tend to buy interesting parts when I see them and the little bag may lie around in my workshop for years until I find a use for them in some or other widget.  Here is a little 12 Volt switcher circuit which took me about 2 hours to find the parts in the depths of my Junque Bochs, and build on strip board: The circuit starts with a self resetting fuse against over current, has a MOV for protection against high voltage spikes, an anti-dumkopf diode, a switching regulator and a couple of electrolitic smoothing capacitors. The big capacitor has a tiny one accross it, to quench high frequency EMI. The two little terminal blocks make

Solar Lantern

One can buy solar powered garden lights everywhere now.  They are useful for lighting up a garden path, outside patio, or your Satnogs ground station, but why buy one if you can build it yourself - at much higher cost of course.  If it would be a rational economic decision, then I'll never build anything! How much current can one get from a small, supposedly 1 Watt, 12 cell solar panel: X-Ray Tube Current According to my ancient 'X-Ray Tube' meter, about 7 mA under my desk lamp! If you want to build one yourself, or repair an existing one that failed, here is a little circuit with only about a dozen parts, that should get you going: There are a few tricks to this circuit.  Solar cells are diodes, therefore one could simply wire a small solar cell panel across the battery to charge it, but solar cells are also cheaply made and full of flaws, meaning that they are not good quality diodes and will slowly discharge the battery when it is dark.  Therefore it i