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From: John Devereux
Subject: Re: V regulator input cap size?
Date: Tue, 22 Oct 2002 22:10:13 +0100
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Lizard Blizzard wrote:
>Frank Bemelman wrote:
>> "DaveC" schreef in bericht
>>>On Tue, 22 Oct 2002 8:10:08 -0700, Lizard Blizzard wrote
>>>(in message ):
>>>Circuit current requirements:
>>> 555s: 10mA each x2
>>> 4020: 1mA max including output drive current
>>> LEDs: 15mA each x2
>>> Relay coil: 25mA (I was a bit off on this figure!!)
>>>Supply voltage measures at 28vac rms. (for some reason it's running lower
>>>than normal for HVAC) which will give ~ 37vdc(?). The max input for the
>> The easiest way is a 7824 followed by 7812. Both should be
>> on a heatsink, you can use a single heatsink for this.
>I searched National's web site and they didn't have a 7824. But
>assuming that the 7824 has the same 35V maximum limit on input voltage,
>he would still have the same problem, the unreg'd voltage would still
>exceed its limits.
Of course it has a higher limit, otherwise why would Frank
have suggested adding it? :) !
It's a good idea. (The voltage limit may still be a bit
close for comfort, though).
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