One of the most fundamental resources for an electronics hobbyist is a good robust power supply. Short circuit and overload protection and precise linear control of voltage and possibly load is essential. The only caveat is, it comes at a cost. A DC power supply from Agilent or Tektronix could easily run up to INR 30k. I decided to build my own, last year.
There's this store called 'Universal Transformers' in SP road, who specialize on manufacturing transformers. I got myself a decent 2A transformer. I assumed it would work up to around 1A or possibly a bit more without any issue. Then got in a bunch of 1N4007 diodes from my stocks and built two bridge rectifiers. The transformer was a center-tap and would give me 15-0-15V. S
o I can output both negative and positive voltages. Smoothened the output with two 1F capacitors and it gave a smooth and steady voltage on the scope.
o I can output both negative and positive voltages. Smoothened the output with two 1F capacitors and it gave a smooth and steady voltage on the scope.
The actual voltage control is through a LM317 and its complement, LM337. These are controlled via two precision potentiometers stuck on the main panel. A cheap 7 segment display voltmeter from eBay finished the display part. A switch controlled whether the voltmeter was showing the positive voltage or the negative. The only problem: LM317 and LM337 operate from 1.25V and -1.25V respectively. This leaves a comfortable 2.5V blind spot. Useless for playing with diodes or anything which requires sub-1V.
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