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Author Topic: Another Item In My Grotto  (Read 12872 times)

burakkucat

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Re: Another Item In My Grotto
« Reply #30 on: June 07, 2012, 01:05:15 AM »

It's late, and so apologies in advance if I'm overlooking the obvious and asking a stupid question, but what does the large push button actually correspond to on the schematics?

The schematics show two apparently independent single pole 'on' buttons, S3 and S4, either one of which would seem adequate, and annotated LH and RH.  Any clues?

Clues? Let's see . . . :hmm:  Hmm, the schematic diagram that you have consulted is for the newer Hatfield Instruments device. I did mention that there was a subtle difference (or two) between it and the original Wayne Kerr  device. The two single pole push buttons, S3 and S4, are on either side of the Hatfield Instruments device. Something to do with equal opportunities for left- and right-handed people! The Wayne Kerr device just has the "on" push button on the left-hand side . . . that is the large push button of your query.  :)
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burakkucat

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Re: Another Item In My Grotto
« Reply #31 on: June 07, 2012, 01:12:31 AM »

Quote
Ah, so your favourite voltage is 6.3v ??

Why, yes, it is. To date, I have absolutely no idea why that particular voltage was chosen. I am referring to the peculiar "extra" 0.3 of a Volt. Why not just 6V ? Ideas, anyone?  ???
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roseway

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Re: Another Item In My Grotto
« Reply #32 on: June 07, 2012, 07:22:48 AM »

Something to do with the typical voltage of lead-acid cells perhaps?

Edit: Yes, that's it - http://www.r-type.org/addtext/add014.htm
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  Eric

burakkucat

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Re: Another Item In My Grotto
« Reply #33 on: June 07, 2012, 06:12:24 PM »

Well I never knew that! Thank you, Eric.

However I suspect there is a minor logic error in the page whose link you have provided. A freshly charged Lead Acid Cell will provide 2V. Three LAC's in series (as in an American car battery of that era) would be 6V. However to ensure that the car battery remained charged, greater than 6V would need to be provided by the car's charging circuit. Hence I assume that is where the "extra" 0.3V comes from.

I seem to have a memory that modern day vehicles, with 12V electrics, can have up to 14V supplied to the SLA battery and so any in-vehicle electrics are designed to be input voltage tolerant -- 10 to 15 volts, I believe.
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roseway

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Re: Another Item In My Grotto
« Reply #34 on: June 07, 2012, 06:43:00 PM »

Quote
However I suspect there is a minor logic error in the page whose link you have provided. A freshly charged Lead Acid Cell will provide 2V. Three LAC's in series (as in an American car battery of that era) would be 6V.

No, that's not quite right. The fully charged voltage of a lead-acid cell is a bit over 2.1V, so a nominal 6V car battery would actually have a voltage of just over 6.3V when fully charged.
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  Eric

burakkucat

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Re: Another Item In My Grotto
« Reply #35 on: June 07, 2012, 06:57:10 PM »

 :hmm:  Hmm . . . b*cat pads off to check his electro-chemistry.  :-\
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sevenlayermuddle

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Re: Another Item In My Grotto
« Reply #36 on: June 07, 2012, 07:04:57 PM »

I must admit, whilst I was probably curious as a youth (among other youthful interests  ;) ) about the 6.3V filaments convention, there was no easy way (pre www) of researching such things and so I suppose I just came to unquestioningly accept it.

Good to see it being discussed again, I'll read with interest  :)
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