Voltage Conversion Query - Help please!

hi

Let me introduce myself to you. Im a guy who knows-nothing-about-anything in electronics, a newbie to electronics. 0% you can say . Please help me with my querries.

I live in Pakistan and here we have 220V power supply to our homes. Our electronics teacher has given us a project to carry out and he has restricted us to use a DC power supply to it (like AA batteries and stuff). He has obliged our projects to be operated on the same power supply on which our home does. Therefore, my question to you is

How can I convert a 220V power input to 3V or less (while developing my project on a stripboard)?

Please use more of the simplified english to explain the answer and also do guide me if I've posted this thread in a wrong discussion.

Thank you.

 

Are you required to design the power supply or can you purchase the supply?

hgmjr

 

yes, we are required to design it. What is the procedure to build such a power supply?

 

Use google to find tutorials on designing power supplies.

Here is just one example of just such an article.

hgmjr

 

Your example was pretty much closer to the topics we've discussed in class. But can u describe (in plain english) as how to put together these components to work (as you see it)?

Im googling though. Lets see what comes as result?

 

I'm puzzled why a man teaching elementary electronics is exposing students to lethal voltages? Are there too many students in the class or something?

 

Well for that, I must say, he has taken steps already. You see, the whole lab has been supplied with power coming from some kindda transformer (step up or step down that I don't remember right now but it does). He has guaranteed our safety.

 

Yeah, we usually use 3V wall warts (We call it "adapters") but, unfortunately, they're forbidden.

Its been only 3 months eversince been exposed to electronics course and guess what?? Im so screwed in it. I never had the brains for it. Although, my concepts are pretty much clear about logics , gates & adders etc but the only thing that pisses me off is implementing them. I guess you'll get the picture.

 

The circuit operates on 3V and What I've available is 220VAC. Im using a stepped down transformer of 12V and its doing well. I've designed my power supply for 5V (using 7805).

Will a 5V power supply enable a 3V circuit of electrical bell??

 

Yes, but it may cause a failure over time. You can place two diodes in series with the bell to drop an additional 1.4 volts. If the bell current is below 50 ma, you can use something like 1N914's. Higher than that will need a larger diode type, like the 1N4000. It's a kludge, but quite inexpensive.