Alt-BEAM Archive

Message #07508



To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Wed, 10 Nov 1999 10:31:08 -0800
Subject: [alt-beam] Re: solar head misery


temporarily connect pins 2,4,6,8 to 0V: never leave HC inputs floating!


Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411

> -----Original Message-----
> From: Jason - [SMTP:evenflow88@hotmail.com]
> Sent: Wednesday, November 10, 1999 8:21 AM
> To: beam@sgiblab.sgi.com
> Subject: solar head misery
>
>
>
> Hie....i dont know why after i wired up the power smart head schematic
> from
> darrel's site(without the SE like the one below)...the thing dont seem
> to
> work...it just stays there even when i cover the
> other LDR on one side...how can i test if my solar head is working or
> not
> cause it
> has been giving me a headache after the whole night of wiring i gave
> up..thanks a
> lot
>
>
> jason
>
> ______________________________________________________
>


7509 Wed, 10 Nov 1999 13:58:19 -0500 [alt-beam] Pots in the head BEAM List Victor Snesarev Hi,

After reading Wilf's wonderful tutorial, I decided to build a PS Head.
Once I started looking for components, though, I found that either a
5MEG pot is not easy to come by, or I am looking at all the wrong places
(DigiKey, All Electronics, ....)

First is a question of naming things. I call a potentiometer a variable
resistor with a longish nob that can easily be turned with fingers, and
a trim potentiometer a boxy-looking device (plastic on the
outside--that's all i've seen) with a tiny screw. Trim pots seem to be
used in photopopers for example. Am I naming these devices by their
correct names -- names that a supplier of these parts would use? Oh, and
then there are tapers, and I think they look more like potentiometers,
but I am not sure.

DigiKey doesn't have any pots over 2MEG. However, All Electronics has a
5MEG linear taper (PC mount pot with 3/16" diameter, half-moon nylon
shaft. Non-threaded bushing.) PC mount, and 3/16" diameter make me
believe that it is one of those small deals that would fit nicely on a
head. Am I wrong?

And the final issue. Since the frequency of the of the HI/LO OSC, and of
Nv/Nu stage is controlled by the resistance of the pots (R1 & R2) and
cap. values (C1 & C2), is it feasible to increase the C's, and decrease
the R's to get the same RC constant and hence frequency? With
approximate values from the tutorial

RC = 2.5MOhms * 0.01uF = 250KOhms * 0.1uF.

I.e. replace the pots by 500K pots and the caps by 0.1uF caps.

Thanks in advance for any info.

Victor



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