> From:         Jinx[SMTP:joecolquitt@CLEAR.NET.NZ]
> Sent:         Saturday, September 27, 2003 8:00 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE:] Newbie Question: Electrical protection for PICs

>> Maybe
>>
>> 3 * 2.1V = 6.3V (lead-acid cells)
>>
>> 6.3V / 2 Ohm = 3.15A
>>
>> Mike.

> Just out of interest, there's an explanation of why valve
> heaters came to use 6.3V in the 9/2003 issue of Silicon
> Chip. According to Vintage Radio columnist Rodney
> Chambers (VK3UG), in the early 1930s valves had various
> heater voltages but it was the efforts in the US to make a
> practical car radio that led to the standardisation of valves
> to run on the car's 6V (used at that time, and as you say,
> actually 6.3V) battery

That's right, although storage batteries were also used
outside of cars for experimenters at home. To match the tubes,
transformers were made in 6.3 (and 12.6) VAC. The battery
use is now gone, but the transformers remain, which is why
home made power supplies have to make due with transformer
voltages that are just a little too low for 5 VDC.

John Power

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