DHT Heater using VCCS - PCB or Kit (Possible Group buy)

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pre65
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#586

Post by pre65 »

1 Gnats Whisker = 0.000" to 0.005" or less (i.e. a light gap).
2 Gnats Whiskers = 1 Gnats todger
3 Gnats todger = A Gnats.
4 Gnats =a Tad
3 Tads = a Smidgen

YMMV

OR

Gnats dick.

An extremely small unit to measure things by, subdivided into a `gnat's dick-end', (about 8 to the gnat's dick), and a `gnat's cock-hair', (about 12 to the gnat's dick-end) thus giving an imperial scale of 96 divisions. This sort of accuracy is essential if you're trying to engineer the worlds best amplifier. :wink:
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Ali Tait
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#587

Post by Ali Tait »

Is a midgie's dick the same as a gnat's todger?
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pre65
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#588

Post by pre65 »

Ali Tait wrote:Is a midgie's dick the same as a gnat's todger?
Depends if it's a black, or white midge. :wink:
The only thing necessary for the triumph of evil is for good men to do nothing.

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Mike H
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#589

Post by Mike H »

You've left out a fly's eyebrow.



:D
 
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Dave the bass
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#590

Post by Dave the bass »

Dave the bass wrote:LD1085 in the BB's though innit, thats what's on the PCB legend? :shock: 1.78V across ip/op pins Andrew, AC i/p to BB is 6.38V AC, so a smidge higher than I'd bargained for. I'll experiment with a small trim down as suggested by Phil and see what happens here mindful of the whole thing falling out of regulation.

DTB
Any updates or thoughts Andrew? I can sub-in LD1084V in 1085's place 'fairly easily' as the amp is only a breadboard project at the mo.

DTB
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#591

Post by Andrew »

Sorry, I think that LD thing was just a typo on my part, it should be a LD1085, no need to change it out.

Andrew
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#592

Post by Andrew »

Andrew wrote:Remaining folk to be delivered...


IPLS 4 + 4BB
Greg 4BB
Lynn Olson 4BB
Little Eddy 2BB
Richard H 2BB
Michaelvv 2 (not answering PMs)

Did I miss anyone?

Andrew
Steve, did I miss you off? So sorry!!!

SS 2 + 2BB

I can bring to Owston for you?

Andrew
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IslandPink
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#593

Post by IslandPink »

If you're there on Sunday afternoon then Owston is fine for me Andrew.
I'll try & tweak Lynn Olson to contact you .
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#594

Post by Andrew »

OK Mark, no problem, I plan on being there on Sunday afternoon.

cheers,

Andrew
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IslandPink
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#595

Post by IslandPink »

Andrew :
Couple of questions :
(i) what values of Rx , Ry should I be using for 20V-out on the big boards ?
(ii) If I'm using an SMPS at 24V DC coming in, could you just confirm where the best place for the +V would be to 'tap in' to the board. The ground connection/plane is fairly easy to see on the underside.
( Edit : maybe just use the + and - on any of the big cap positions ? )

(iii) If you have time could you add (i) and (ii) info to the 'Stacks' section, please ?
"Once you find out ... the Circumstances ; then you can go out"
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#596

Post by Andrew »

IslandPink wrote: (i) what values of Rx , Ry should I be using for 20V-out on the big boards ?
Its basically Vout = 2.5v(1 + Rx/Ry), something like 6k8/1k might be a good place to start.

It's all in here. http://www.ti.com/lit/an/slva445/slva445.pdf

(ii) If I'm using an SMPS at 24V DC coming in, could you just confirm where the best place for the +V would be to 'tap in' to the board. The ground connection/plane is fairly easy to see on the underside.


Hold the board longwise, so the horizontal axis is the longest axis, make sure its face up, screen print in front of you, now make sure the diodes are in the top left hand corner. OK?

Right, now flip it over along the horizontal axis, do you see a 'T' block of polygon where the plus of two of the big caps are connected? The block of signal feeds the top pin of the voltage reg, I would pick one of those holes, probably the nearest one.


( Edit : maybe just use the + and - on any of the big cap positions ? )
(iii) If you have time could you add (i) and (ii) info to the 'Stacks' section, please ?
Will do.


Andrew
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IslandPink
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#597

Post by IslandPink »

Thanks !
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IslandPink
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#598

Post by IslandPink »

thomas wrote:......once I was reliably informed what I took to be links were in fact the sense resistors!...
Now, I need info on this bit. Is Rs a sense resistor and therefore in series with the filament - for measuring the current ?
Can I bridge this with wire if i don't need it ?
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#599

Post by Andrew »

The wire link is the sense resistor for the VCCS part of the reg, its an integral part, even if you're using a different supply you need that link.

Andrew
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#600

Post by IslandPink »

I'm not sure I understand the answer .... :(
Do I put a resistor in there ( if so what value ? ) or do I put in a piece of wire ?
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