16-05-2011, 07:53 PM
I keep an archive of articles that have interested me over the years, of a range of topics, one of which is power supplies. I recently searched for something suitable for a low power regulated PSU for the lathe RPM meter that I'm building, and in that connection, I rooted out an article from July/Aug 1978 Elektor magazine. It didn't quite fit the bill, so I designed my own PSU and circuit for that project, but it occured to me that the PCB in the Elektor design was so small and neat, that others might like to bear it in mind. It would especially lend itself to low-powered test gear which is used infrequently, by which time you find that not only is your 'pound shop' PP3 flat, it's probably leaked and corroded the connections. This little unit is compact and cheap to make, and only needs the addition of a small mains transformer to suit the desired regulated voltage. The PCB is just 40mm x 45mm, (about 1.75" square(ish).
Depending on which voltage regulator is chosen, you can have any Voltage from 5V to 24V but I guess the most popular would be either 5V or 9V, though oddly, the table mentions 5, 6, 8 & 10V, but not 9V, though 9V regulators are commonplace.There is a table which shows the minmum and maximum voltage from the transformer which is required to get the full 100mA regulated output at the desired voltage. The table also shows what value and working voltage rating is needed for whatever is the chosen voltage. Small transformers are avaiable from the lieks of Rapid, for no more than a fiver, and the other components would be no more than two pounds apart from the PCB. For those with no PCB making facilties, perfboard could be used just as well, with the layout along similar lines.
The article is now 33 years old so has yellowed with age, just as my hair has gone grey in sympathy, so the artwork isn't suitable for copying directly as a PCB mask onto inkjet acetate. Hence, I've cleaned it up in Photoshop and added that below, along with the article.
I hope it's of interest.
David
Depending on which voltage regulator is chosen, you can have any Voltage from 5V to 24V but I guess the most popular would be either 5V or 9V, though oddly, the table mentions 5, 6, 8 & 10V, but not 9V, though 9V regulators are commonplace.There is a table which shows the minmum and maximum voltage from the transformer which is required to get the full 100mA regulated output at the desired voltage. The table also shows what value and working voltage rating is needed for whatever is the chosen voltage. Small transformers are avaiable from the lieks of Rapid, for no more than a fiver, and the other components would be no more than two pounds apart from the PCB. For those with no PCB making facilties, perfboard could be used just as well, with the layout along similar lines.
The article is now 33 years old so has yellowed with age, just as my hair has gone grey in sympathy, so the artwork isn't suitable for copying directly as a PCB mask onto inkjet acetate. Hence, I've cleaned it up in Photoshop and added that below, along with the article.
I hope it's of interest.
David