Temper Electronics Experts I need YOU!

[Jamstruth]

For a physics project in school I am planning on building an AC->DC rectifier with a 5V output (i.e. USB spec) but I'm having a bit of trouble with Diode Specs. Specifically the Zener Diode at the end that I'll need to get the output voltage smoothed correctly (the regulator). I'll need one with a 5V value and I can then try and tune the rest of my parts to that. So if anybody could give me a hand finding all the parts and specs I need it would be great (any data sheets greatly appreciated as I need references). I need a capacitor, 4 diodes (of same spec so 1 really) and a resistor to keep current down so the Diodes aren't burnt out.

ANy help out there tempers?

 

[nryn99]

i know a little something about these guys so i'll try to find something for you.

EDIT: ahh...
different diodes
http://www.radio-electronics.com/info/data...cs-tutorial.php
http://www.globalspec.com/Specifications/S...es/Zener_Diodes
http://www.ee.latrobe.edu.au/internal/work.../datasheet.html
http://sound.westhost.com/appnotes/an008.htm



i don't understand this much but this might help:
http://engknowledge.com/power_supply_design.aspx
http://en.allexperts.com/q/Electrical-Engi...imple-AC-DC.htm

NOTE: i'm not sure what you're looking for so i just threw in what i found that i think you might need.

 

[FAST6191]

They let you play with wall voltages? Not bad.

Going for a Zener Diode as a regulator? Personally I would use a standard IC style regulator but I guess this is schoolwork so such niceties are not going to happen.
http://www.kpsec.freeuk.com/powersup.htm pretty much covers what I would type out with regards to various design ideas. http://www.kpsec.freeuk.com/powersup.htm#rectifier has the Zener "equations" at the bottom.
http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm is quite nice but not reference material really.

Still USB is 500mA for a single port which is quite a lot so you are going to need a bigger zener than the standard little things you see kicking around parts bins.
Your main problem will be that 5V is not really a common Zener voltage (5.2V is available and within the 10% or even 5% safety allowances/tolerances most electronics types work to- you could also add a resistor to the output I guess or if you prefer to low ball it 4.7V is available).
I am having a bit of trouble tracking them down but http://uk.rs-online.com/web/search/searchB...205W#breadCrumb should get you something.

The resistor for such a current ranges also needs to be fairly good (have a high power rating)- this places you in wirewound territory. You say USB "charge" type arrangements so that is fine but remember for future projects wirewound resistors are fairly good inductors and so will probably annihilate any signals you might get.
http://www.rapidonline.com/Electronic-Comp...77/kw/wirewound

If I can persuade you to go the IC route* then 5V is easy http://www.rapidonline.com/Electronic-Comp...ge+regulator+5v granted this one is surface mount. If you want through hole type things then http://www.rapidonline.com/sku/Electronic-...s/29653/47-3290

*if you need to justify it then these things have lots of internal checks and balances, shutoffs and what have you.

Diodes for the bridge- you can get diodes that can take straight wall voltage AC (and beyond) these days to save you messing with a transformer. You pretty much just need a diode capable of taking the current (consider it 600mA at this stage at least) and not having a breakdown voltage below that of the transformer output (probably going to be around 7V but if you can get nearer 10V that will be better. Leakage current you can probably ignore for this one and forward voltage drop should not be that bad as long as you have the current rating suitably high (there is little point in manufacturing a rectifier grade diode and having it drop the voltage across it). Again you can buy straight up bridge rectifiers.

Datasheets for all the components are on the links- all good electronics shops will have them readily available.

As an aside apart from being one of the few good electronics companies supplying stuff in the UK rapid also have fair ties to education so you might not have work too hard to get stuff (your school might well already have an account with them) and it saves you having to deal with maplins.

 

[Jamstruth]

Wall Voltages? Pah, we have a 5kV PSU that we can use if we need (doubt it though) Was waiting for you to reply FAST. I remember you by your Walrus avatar, not by your username otherwise I might have just PMed you.

I'll likely be using the school's relatively inaccurate supplies to step the voltage down a bit first instead of my own transformer. Saves me any huge resistances to step it down. There are some pretty good variable ones I think. If I was to use another style of regulator it would be more electronics engineering than Physics. I'm going to be doing demonstrations on the properties of each component first to flesh out my investigation (Reverse Voltage Max, Capacitance, Zener Conductivity etc.) So if I don't know how these things are constructed or they're just made up of various parts I've used before then there is little point in using them and trying to demonstrate what they do. I'd need to demonstrate it outside of the Rectifier Circuit if possible.

As for the Zener voltage +/- a bit is fine, the 5V output is just a target so I could maybe do a bit of messing with an old phone charger and stick an old phone on the end to prove it has a practical use, no idea where they're chargers are to check that it will actually work though. They're old enough not to have any USB connection stuff and therefore might have weird voltages.

 

[FAST6191]

High tension is fun to play with but I am more apprehensive dealing with wall stuff than that (HT stuff is usually fairly low current aside from stuff like http://www.lucidscience.com/gal-rock%20disaggregator-1.aspx ).

Yeah phones have odd voltages- I was given a bag of old ones the other week and they run the gamut from about 3.4V to 7.something

Equally most of those datasheets have internal parts lists and circuit layouts in them ( http://www.rapidonline.com/netalogue/specs/47-3290e.pdf page 3 in internal numbering for instance)- if nothing else you can compare yours to a commercial one and say how they differ- kind of like how you get taught equations of motion but can demonstrate how they adapt to more realistic conditions.