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?

 

The first component you need is a transformer, it dictates the rest. How are the component sources in that region? Will he allow you to get a wall wart (an unregulated power supply that plugs directly into the wall outlet) and then build a regulator?

For what it's worth, they didn't have wall warts when I was a kid, I pretty much had to build everything related to power supplies in the project. Maybe it has influenced my thinking, but I don't see it as a big deal (high school stuff) as long as you pay attention and follow safety guidelines (example, a fuse is a must!).

If wall warts aren't acceptable, then you'll need an enclosure. You will want to surround the power supply so there are no exposed wires, like Steve said, these are lethal voltages.

Check out the All About Circuits for building techniques. You can make enclosure out of wood and use terminal strips for most of it.

Given you're lack of experience I do suggest the wall wart route, you can build a regulator (which is the important part).

 

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.

 

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.

That was particularly important information. We need details in order to help. It would have to be step down, basically we need the AC voltage you will be working with.

http://www.allaboutcircuits.com/vol_2/chpt_9/index.html

http://www.allaboutcircuits.com/vol_3/chpt_3/4.html

Note to moderators: This is shaping up as homework from what I'm reading.

 

The first component you need is a transformer, it dictates the rest. How are the component sources in that region? Will he allow you to get a wall wart (an unregulated power supply that plugs directly into the wall outlet) and then build a regulator?

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

when I was a kid, I pretty much had to build everything related to power supplies in the project.

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.

 

OK, back to basics though, what is the stepped down voltage you have to work with? I assume 50 Hz, since I don't have a clue what Pakistan standards are.

So before anyone can help, we need the following.

What is the AC voltage you have to work with? We've got contradictory answers on that one. If you have to start with 220VAC then it isn't safe, but it is doable.

How much output current and voltage do you need?

What kind of parts access do you have?

 

What is the AC voltage you have to work with? How much output current and voltage do you need?

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.