| |
G4EBT > TECHY 27.09.03 16:53l 61 Lines 2128 Bytes #999 (0) @ WW
BID : DF1581G4EBT
Read: GUEST OE7FMI
Subj: Neat 10A 13.8V Homebrew PSU
Path: DB0FHN<DB0RGB<DB0FSG<DB0ZKA<DB0KFB<DB0CZ<DB0GE<DB0GV<DB0SIF<DB0EA<
DB0RES<ON0AR<WB0TAX<N1UAN<ZL2BAU<GB7FCR
Sent: 030927/1441Z @:GB7FCR.#16.GBR.EU #:16948 [Blackpool] FBB-7.03a $:DF1581G4
From: G4EBT@GB7FCR.#16.GBR.EU
To : TECHY@WW
Following on from the thread of PSU's, I came across a neat 10Amp 13.8
Volt homebrew PSU design on an excellent website I've revisited, having
not looked at it for some time. The PSU is, like the Manson/Palstar types,
is based on the ubiquitious LM723 regulator IC, and 2N3055 pas
transistors.
The website is that of the Radio Amateur Society of Norwich - R.A.S.O.N
(Norwich in the US of A that is - not the "sleepy hollow" market town
in the back of beyond in East Anglia).
All credit to Mike Martell, N1HFX who had put 26 most useful and varied
projects on the website, plus lots of other stuff.
Interestingly, he touches upon the risk of emitter to collector shorts
which can lead to an overvoltage situation, with potentially dire
consequences for any expensive gear attached to the PSU. What he says
in conenction with design considerations for his homewbrew PSU
is, to some extent, reassuring for users of PSU's such as Manson/Palstar,
which have no overvoltage protection:
Quote:
"Although it isn't really needed due to the type of current limiting
circuit used, over-voltage protection can be added if desired. The only
way that over-voltage could occur is an emitter to collector short, and
although this can happen, it is much more likely that an open circuit
will occur".
Unquote.
Mike purposely destroyed several 2N3055's by shorting emitters to ground
to see what the effect would be, and all went open circuit. He does
however, include as an add-on a crowbar over-voltage protection circuit
consisting of only four components - as Zener diode, an SCR, a cap and a
resistor. This would make an easy outboard add-on for any PSU such as the
Manson EP925/Palstar etc, for added peace of mind.
Take as look at this and the other projects at:
http://www.rason.org/Projects/projects.htm
(Note that the first "Projects" in the URL has an upper case P)
Enjoy!
73 - David, G4EBT @ GB7FCR
Eddystone User Group Member
G-QRP Club Member No: 1339
QTH: Cottingham, East Yorkshire.
david@crofters89.freeserve.co.uk
Message timed: 23:09 on 2003-Sep-26
(Registered).
Read previous mail | Read next mail
| |
