home built power pac

[Anonymous]

Hello, I am looking for a schematic for a home built power pack using no transformer but the 2n3055 power transistor for stepping down the voltage. I am not using it for a model railroad but as a display for a 4-H fair. I remember way back that there was an article on one and could not find it. If anyone can direct me in thr right direction i would appreciate it. Thanks...[:I]

[Anonymous]

I don't want to discourage you from building one it you really want to, but these days its really easy and cheap to buy something already built. My favorite place to buy electrical and electronic stuff online is: http://www.allelectronics.com/

Good luck!

[Anonymous]

I am trying to show the difference between a regular transformer power supply and one with silicon regulators and transistors. I would like to set them up by stages and really show the differences in a large display for people to see. I am going to be putting this on a two by two foot board and on one half the one type and the other below it. With explanations of the differences between them showing people the benefits of silicon and transistors and such. I kind of need a schematic for this to work. Thanks.

[jrbarney]

QUOTE: Originally posted by jeffchele

Hello, I am looking for a schematic for a home built power pack using no transformer but the 2n3055 power transistor for stepping down the voltage. I am not using it for a model railroad but as a display for a 4-H fair. I remember way back that there was an article on one and could not find it. If anyone can direct me in thr right direction i would appreciate it. Thanks...[:I]

Jeff,
I did a search at the Index of Magazines using "power supply" as the search term:
http://index.mrmag.com/tm.exe?opt=S&cmdtext=power+supply&MAG=ANY&output=3&sort=A
You might want to scan some of the more recent handbooks cited at your LHS to see if one has the circuit schematic you need. Also, your local public library should have an index of periodicals, whose title I forget, that you can search for articles in the popular do-it-yourself electronics magazines. This is your 4-H project, you may have to do some of the research. Good luck.
Bob
NMRA Life 0543

[nfmisso]

Jeff;

For UL® safety compliance, you need some sort of isolation such as a transformer. A transistor does not cut it.

Further more, a 2N3055 does not have sufficient voltage capability to be connected directly to 120VAC lines - it will blow. Further requiring a step down transformer.

I suggest that you show the difference between a transistor throttle and an old fashion reohstat throttle, both using the same step down transformer. With the reohstat you could show the need to add load compensation resistors. With either, you could show the additions required for momentum, etc.

e-mail me directly if you want to discuss this further.