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G8MNY > TECH 01.01.03 15:17l 34 Lines 1518 Bytes #999 (0) @ WW
BID : 35554_GB7CIP
Read: GUEST OE7FMI
Subj: PS for Floating Pb batts
Path: DB0MRW<DB0RGB<DB0FSG<DB0ZKA<DB0KFB<DB0CZ<DB0GE<LX0PAC<LX0HST<HA3PG<
7M3TJZ<OZ2DIZ<GB7YKS<GB7LGS<GB7TUT<GB7CIP
Sent: 030101/0943Z @:GB7CIP.#32.GBR.EU #:35554 [Caterham] $:35554_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
One power supply I have used for my packet system, which is a floated on gel
type battery was to use a 12V regulator IC 7812 & offset adjustment to get the
O/P up to 13.5V which is the max for gel types in float use.
in _______ out
+22V ------------------!_______!---------!>!-------- +13.5V
RAW DC ! 7812 ! ! 1N4001 FUSED
FROM >1000uF --- ! --- FLOAT
BRIDGE 30V === VR 10K --- 0.1u BATTERY
RECTIFIER ! ! !
0V -----------------------------------------------
Because it is for a float battery & I don't want any back discharge on no mains
I put a 1A diode in series with the battery.
A variable R in the common leg of the regulator (multiturn say 10K?) will vary
the O/P voltage as the regulator puts a constant current (typically 50uA) out
on the common leg.
The regulator I/P needs to be at least 18V DC for the max 1A O/P & the
regulator will need a heatsink (insulation kit?), so the transformer (18V AC),
bridge & cap need to be able to supply this.
The 0.1uF cap across the regulator O/P are for stability.
For 6V battery, use a 5V regulator IC 7805, & adjust for 6.95V.
For much less current than 1 Amp use 78L12 or 78L05 for 100mA Max. All
regulators of this type are current limited just over there maximum current,
they also have thermal shutdown.
73 De John, G8MNY @ GB7CIP
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