11-05-2011, 03:11 PM
Thanks, Chris.
Amongst the wide-range of test kit that one can make, linear PSUs must about the easiest to design and build. Layout is not particularly critical and choosing the necessary components is fairly straight-forward if the basic electrical parameters of the devices are known; most calculations are simply applications of Ohm's Law and a few power calculations. Adequate mechanical strength, insulation & safety, surge protection, adequate voltage, current & power ratings and the provision for the escape of excess heat seem to be the limiting factors. Being tight-fisted as I am, it's nearly always a question of "What have I got in the junk box?" when the need arises.
The only other point I will stress is the importance of thoroughly 'soak testing' the finished item on full load before declaring that the item is Fit For Purpose. This is particularly relevant when solid-state devices are employed, since Vbe junctions (and similar - like Zener diodes) can vary substantially at elevated temperatures compared to the 'nominal' 25°C.
Al.
Amongst the wide-range of test kit that one can make, linear PSUs must about the easiest to design and build. Layout is not particularly critical and choosing the necessary components is fairly straight-forward if the basic electrical parameters of the devices are known; most calculations are simply applications of Ohm's Law and a few power calculations. Adequate mechanical strength, insulation & safety, surge protection, adequate voltage, current & power ratings and the provision for the escape of excess heat seem to be the limiting factors. Being tight-fisted as I am, it's nearly always a question of "What have I got in the junk box?" when the need arises.
The only other point I will stress is the importance of thoroughly 'soak testing' the finished item on full load before declaring that the item is Fit For Purpose. This is particularly relevant when solid-state devices are employed, since Vbe junctions (and similar - like Zener diodes) can vary substantially at elevated temperatures compared to the 'nominal' 25°C.
Al.
