Make cool gadgets from a deceased fluorescent lamp

Step 3 Schematic

This is the schematic. 555 drives the Mosfet and it pulses current thru the inductor L and the load. Once Mosfet is off, the magnetic fiel collapses and a voltage with oposite polarity appears on L terminals, thus the Schotsky diode conducts this energy in the form of current to the load, but at the load the polarity remains unchanged. The resulting formula is this: Voutput=Vinput/Duty Cycle. Because power losses are like 15-20% you just need a small heat sink for the mosfet. Believe me, I had one linear converter using a LM317, and it got very hot, even though it had a large heat sink.

Comments

[acmefixer]

The Schottky rectifier could be a 1N5819 if the current is not too high. This diode is limited to 1 amp max. There are 3 amp versions, 1N5822, I believe

Warning. There is no current limiting in this circuit. The input should have a fuse.

[Sagar Gondaliya]

can you put in a "real" schematic insted of this hand drawn one?

[unknownpocketnerd]

Sorry, I used a DOS version of ORCAD then printed them and scanned them. My old matrix printer is mechanically damaged. Freeware for electronic design are very limited in their libraries of symbols. Do you have a link to a good piece of freeware that has a good bunch of symbols?

[acmefixer]

ExpressSCH is a part of ExpressPCB, freeware from expresspcb.com. It doesn't have a very good lib, but with a little time and effort you can make your own. I've also used the other part, ExpressPCB, to design PC boards, but you are limited to using their services for making the boards.

[cyberpageman]

I think your schematics are great. It's a pain to draw them by hand and you did a nice job.

I've tried TinyCAD, which is free and easy to use for schematics. http://tinycad.sourceforge.net/

[spacemoose]

I had a look at dai, which I personally use for UML drawings. It seems to have all of the symbols which you need, and I find a pretty usable program.

I have access to Illustrator through work, and i do a lot of technical drawings: Scientific figures, documentation for code and applications. In the situations where it is applicable (UML diagrams, electric circuits) it's my first choice application. It's simple and provides just the important features. This makes it quite efficient and easy to use for the kind of stuff I need to do.

It's a really old school drawing program, orginally implemented under X-Windows, but it's recently been ported to Gnome. There is apparently a windows version: http://dia-installer.de/index_en.html
It is of course GPL'd.

[spacemoose]

whoops, I should have proofread more closely. In the second paragraph, my intent was to say that DIA is my first choice application, rather than illustrator. I only whip out illustrator when I have to something kinda fancy.

[unknownpocketnerd]

Thanks. By the way, I have all of Forrest Mims' Engineer's Mini-Notebooks, by Radio Shack. Forrest drew them all by hand, no typing, no CAD, just good old fashioned schematics. I think this series was his Masterpiece. So I try, in my own way, to emulate him. I don't like to use computers for everyting, except for programing, but computer drafting seems a bit constrining.

[acmefixer]

Don't try to emulate him. I also have most of his manuals. Beware! You will most likely be very frustrated when you build from his schematics and find that it doesn't work. They are full of gross errors and omissions

[cyberpageman]

Yes, your drawings are very similar to Forrest Mim's sensible schematics. I have many of his notebooks and value them.

[bit_bucket]

Great guy still living in TX with his family, Did you know he corrected NASA and a temperature calculation used in global warming with electronics he built on his farm? The joke at the nearest radio shack when parts are missing like LEDs is that the last guy in the store was him! I keep missing him lol

[cyberpageman]

Thanks for the clue. Because of what you said, I looked him up on the Internet. He has a couple of websites, http://www.forrestmims.org/ and http://www.forrestmims.com (which sells his books), as well as several science sites. Amazing guy.

[Sagar Gondaliya]

I use a software called ExpressSHC which has a bunch. it has all the symbols that you have on your schematic plus more. look it up on google. the download takes like 10 minutes but its free and works great. also, if your a really big electronic geek like me, the program automatically downloades a program called ExpressPCB. you link your schematic to it, send it to the site, and they send you a printed circuit board for it.....for a price of course. I used it to make a bunch of tv remote jammers (KipKay) and it's a lot easier to use than veroboard.

[zippoge]

i think you forget pin 6, it must be connected with pin 2 

[unknownpocketnerd]

you're right!  Sorry for that inconvenience.  Folks, please acknowledge this tip:  Pins 2 and 6 are wired together.

[Nerdz]

What is the max current this device can put out while keeping the same voltage? Do you have to adjust your output once you have the device connected? Ive been wondering about the same thing, but instead of using a Pot, use a feedback section (which is just two resistors connected as a voltage divider on the output) and connect it to pin 5. This way, the device would be self regulating and you wouldnt need a pot to set your output voltage.

[unknownpocketnerd]

Sounds worth trying!