[Show Suggestion] 5V power supply.

[masherscf]

There are certainly 5V power supplies available commercially. However, I was thinking about a build that would be fairly simple in order to practice soldering, circuit building and to built confidence using 120V AC power.

My idea is a 5V power supply. The parts are fairly simple. A transformer, some diodes, a power switch, an indicator LED, a power cord and a few capacitors to smooth out the voltage.

You can do the entire built from start to finish. You can even get crafty by putting it it's own kit box. Drill the holes for it. Hook it up to the oscilloscope. You can talk about the practical layout of a home-built device.

As you may know, My BS is in physics. One of the first courses they make you take is a course in Scientific instrumentation. That is, a course in building our own instruments. That was about 20-years ago. We has just a few basic ICs available. The idea of programmable ICs seemed like science fiction. Things have sure come far.

The beauty of the build is, now you can use the 5V supply to power all your other projects.

[tokenuser]

The beauty of the build is, now you can use the 5V supply to power all your other projects.

This is a great idea. Also remember that 5V is what USB delivers, so adding in a USB port as a charger (at the appropriate ampage) would be a neat project.

[mikec]

Why not also have them show how to wind a transformer? The electronics 101 class from many years back taught us how to do that. I think that brick is still somewhere at my parents home.

I think we got 12v off of one set of taps and 6v off the other.

[scienceking]

Using zeners to build your own rectifier is really inefficient compared to using an off the shelf rectifier IC. ON Semiconductor(Motorola's Power spinoff) and a few other companies have lots of great little IC devicies geared toward efficient power supplies. Also, I'd recommend building a switch mode PSU if you were to plug it into AC power, and then regulate at the device side. Switchmode PSU design lets you provide more than a few hundred mA current by your PSU, which is probably a good idea for a hobbiest to have. Also, for safety's sake, you should always use fuses at the very least when debugging circuits that you plan on running on the mains, as they can catch on fire in the event of an overlookd short, and they can burn your house down as a result. And mind you that fuses do little to help you from dying if that short happens to go through you, so be careful.

[masherscf]

And mind you that fuses do little to help you from dying in that short happens to go through you, so be careful.

I guess one of the goals is to build confidence and respect for electricity. Practicing some practical soldiering would be good...

I wish I would have had more practice before I bricked my first PS1 installing a mod chip. :(

[scienceking]

Practicing some practical soldiering would be good...

Unfortunately, soldering is more of an art than a science. The old tech who trained me at my first job to do PCB modification and prototyping gave only one rule for soldering: If it hurts, don't do it. One good piece of advise for practice is to find an old surface mount/pin through hold mix PCB from the 80s(so that the ICs and stuff are bigger, you can find them in old printers and stuff), and just desolder and resolder the components. This can help you practice techniques like tacking ICs and getting the motor skills for flowing solder just right.

And like any hands on activity, the solderer is only as good as his tools. Have a good iron that can deliver a lot of energy and keeping it clean with tip tinner and such can be the difference between a frustrating time and an easy go. Those weller and hakko irons might look expensive, but they really are worth it over the el cheapo ones. Soldering is all about chemistry, so keep this in mind when understanding whats going on or why the plating on your iron tip might make a big difference. Other tools that really make a difference are knowing how to use flux properly(both pastes and pens, they all have a place), knowing how to flow solder already wetting the tip onto pads/joints, and make sure you have a solder sucker but also some braid too.

Braid is good for cleaning up joints a bit if you add too much solder to them. This is a big problem for ICs as sometime I'll add a bit too much to one pin and then when I try to solder the pin next to it, ill invariably heat the last pin's solder and create a bridge between the pins...a bit of braid will fix that quick!

Lastly, if you plan on doing a ton of work, or modifying commercial circuit boards that use really small pads/traces, magnifier glasses or a stereo microscope can really help you see what you are doing for hours without eye strain. The microscopes can be really expensive but are worth it. There are some good deals you can find online though.

You'd be amazed what you can do with a couple months of experience at this. For example, a friend of mine at my school was doing a DIY projector project, and accidentally chipped the edge of the PCB of his monitor panel while installing it. I was able to successfully sand down the traces and run about 10 wires to bridge the PCB again. It worked fine after surgery. Sure was nice saving him $200 for about 10 cents of wire and solder!

If you have a Fry's Electronics nearby, they have a whole aisle for soldering stuff. Its a good place to at least explore the different products out there. But for buying, online retailers usually sell the same stuff for up to 20% less.