Hi, I'm the newest member to the Arduino community. I'm from Sri Lanka and just ordered my UNO board. I'm posting this while it arrives by mail.
So I did some initial reading to get things started, and thought of building a power supply myself. (Since I'm from a poor country and can do without spending additional money for a power supply that costs as much as the board itself)
So here's my thinking. I have several old radios with a few big transformers. (like 100g) I scrapped one, used the Multi-meter to find out that it outputs an AC voltage of 16V or so. (Sri Lanka has 230V, 50Hz if that's important)
So along with my UNO board, I ordered a few diode bridges known as KBP310 (rated for 3A), and a few 78XXs of 5,9,12 and 15V. These are much cheaper than the power supply prices obviously. I ordered DC jacks as well.
What I expect to do is this. Hook up the transformer to mains AC, then get the 16V from the other side and run it through one of the KBP310s. That should give me a rectified 16V right? Then I would like to use the 78XX to get my 9V. That will go through a DC jack and make my power supply. (add a few cosmetic stuff like tapes, AC plug to make it look better and safer if needed)
So my question is, will this be an okay way of powering my UNO board? Will the voltage from 7809 be steady enough for the job? I don't care about the efficiency at all, and have heatsinks that I can scrap from other old equipment if heat is an issue. If needed, I could spare other 78XXs so it goes like 7815 at the bridge, then it goes to a 7812, and it goes to a 7809. Is that necessary and enough for a stable enough supply so that my UNO will work without issues?
I just want to avoid spending a huge amount on a power supply. Even if I use three 78XXs like above, the whole thing costs me less than 1/5th of a power supply. If I can get away with just 7809, it's like 12 times cheaper.
Sorry if my English is horrible. But I hope my question is clear enough. Any thoughts from an experienced persons on this subject are welcome.