[time-nuts] Parallel voltage regulators

[Don Collie]

Bollocs, Bruce! If National say it will do it, you can bet that it will. An 
LM338K will do the job too, but in my opinion it`s overkill, and in the 
event of a short circuit on the output of the regulator the current for the 
LM338 will only be limited to [.......he gets the book......] 8 Amps [Typ], 
as against 2.2 Amp [Typ] for the LM317T. This would probably be too much for 
the transformer, rectifiers, and smoothing capacitor, effectively meaning 
that you would have no current limiting. If the input/output differential 
was kept in the range of 5 to 10 Volts, while the oven was stabilising, and 
the LM317 had an adequate heatsink, it would do the job nicely [and cheaper 
too!] Actually, it wouldn`t matter if the oven supply went unregulated while 
the temperature was stabilising, because you wouldn`t be using it for 
measurements during this time anyway - or is that a bit radical!?
All the best!,..................................................Don.
----- Original Message ----- 
From: "Bruce Griffiths" <bruce.griffiths at xtra.co.nz>
To: "Don Collie" <donmer at woosh.co.nz>; "Discussion of precise time and 
frequency measurement" <time-nuts at febo.com>
Sent: Thursday, October 25, 2007 5:42 PM
Subject: Re: [time-nuts] Parallel voltage regulators


> Don Collie wrote:
>> Hi Tom,
>>     If you really want to regulate the oven`s supply voltage, my National
>> Voltage Regulator handbook shows that the LM317T will supply over 2 Amps,
>> with an input/output differential of between 5, and 12.5 Volts. A single 
>> one
>> of these should do the job OK.
>> Cheers!,.................................Don Collie jnr.
>>
>>
> Never rely on typical specs always use the minimum spec which is 1.5A
> not quite enough.
>
> Bruce