[time-nuts] Thunderbolt monitor

Thomas A. Frank ka2cdk at cox.net
Thu Jul 17 00:05:42 EDT 2008

On Jul 16, 2008, at 10:46 PM, Didier Juges wrote:

> One issue with the Noritake display (common to all VFD devices) is  
> that it
> draws over 100mA of current at 5V. A 3 terminal linear regulator  
> running
> from 12V will need a reasonable heat sink to operate. A better  
> choice would
> be a small switching regulator such as the LT1375 which I have used  
> in a
> great many products. It's a small 8 pin device that requires only a  
> handful
> of external components to convert 12V to 5 with excellent  
> efficiency (no
> heat sink required). I may lay out the PWB for both types of  
> regulators,
> depending on the type of display you want to use.
> Didier KO4BB

Why would you run this external box off of 12 volts?  Do you have  
portable use in mind?

I ask because to my way of thinking, I would provide the display/ 
processor box with 5 volts straight out of a "wall wart"; I've  
probably got a dozen in that voltage range lying around (left over  
from ZIP drives).

The only use for 12 volts in the display box would be for the RS232,  
and that can come from a MAX232 chip.

Seems like a simpler approach to me.  If I really wanted portable,  
the 12-5v unit would be external.

Tom Frank KA2CDK

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