Alt-BEAM Archive

Message #07485



To: beam@sgiblab.sgi.com
From: "Jason -" evenflow88@hotmail.com
Date: Wed, 10 Nov 1999 06:05:20 GMT
Subject: [alt-beam] Re: solar head questions..





>From: Wilf Rigter
>Reply-To: beam@sgiblab.sgi.com
>To: "'beam@sgiblab.sgi.com'"
>Subject: RE: solar head questions..
>Date: Tue, 9 Nov 1999 16:15:18 -0800
>
>Well I would say, "read the manual" but seriously,
>
>1.what motor driver?
>
>2.Without the solar circuit ie battery power the light stays on. Darrell
>added the FLED to "attract attention" to the solar PShead when it is ready
>for action.
>
>3.That certain component wouldn't be pin 6 and 8 of the HC240? Those should
>be connected to 0V (instead of floating as shown on Darrell's layout
>drawing. Also make sure you add a small (eg 10uf /10V) electrolytic
>capacitor from pin 20 to pin 10. The actual cap value does not matter much
>but it should have relatively direct connections with short leads. This
>stops high frequency oscillations which upset normal circuit operation.
>
>Keep em coming guys and do read the manual.
>
>regards
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493
> fax: (604)590-3411
>


Wilf,

I would like to know if i could make a solar head out of these stuff i had

1.)servo
2.)a few 74AC240
3.)enough caps and resistor for the PSH V.1
4.)1381J
5.)six small calculator solarcells which rates 3.5V each...

do u think i need a motor driver or something...thanks a lot

______________________________________________________



7486 Tue, 9 Nov 1999 22:05:49 -0800 [alt-beam] Re: solar head questions.. "'beam@sgiblab.sgi.com'" Wilf Rigter the big cap has high resistance to high frequencies.

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

> -----Original Message-----
> From: SG [SMTP:Sparkyg@seark.net]
> Sent: Tuesday, November 09, 1993 9:16 PM
> To: beam@sgiblab.sgi.com
> Subject: RE: solar head questions..
>
> At 04:15 PM 11/9/99 -0800, you wrote:
> >make sure you add a small (eg 10uf /10V) electrolytic
> >capacitor from pin 20 to pin 10.
>
> hey wait a sec....
> since + and - from the storage cap go directly to 20 and 10,
> i don't see how another 10uf's would change anything.
>
> or am i missin sumpthin here?
> -Sparky



7487 Wed, 10 Nov 1999 01:15:43 -0500 [alt-beam] Re: solar head questions.. beam@sgiblab.sgi.com Victor Snesarev

SG wrote:

> At 04:15 PM 11/9/99 -0800, you wrote:
> >make sure you add a small (eg 10uf /10V) electrolytic
> >capacitor from pin 20 to pin 10.
>
> hey wait a sec....
> since + and - from the storage cap go directly to 20 and 10,
> i don't see how another 10uf's would change anything.
>
> or am i missin sumpthin here?
> -Sparky

From Wilf's earlier post:

"Also make sure you add a small (eg 10uf /10V) electrolytic
capacitor from pin 20 to pin 10. The actual cap value does not matter
much
but it should have relatively direct connections with short leads. This
stops high frequency oscillations which upset normal circuit operation."

I will try to add more detail, but as I am not an expert by any measure,
feel free to jump in and set me right, anyone. It'll only help me
understand this stuff better.

The cap doesn't add much at all (can consider it's contribution to be 0)
to the storage of the storage cap. It is there to compensate for noise
on the power and ground. It has to be a fast switching capacitor to be
able to compensate for high frequency (tiny duration) spikes and dips in
power. Those spikes and dips occur when lot's of transistors inside the
chip switch at the same time, and in general if there's lots of noise in
the system from whatever source. When a dip in +V (power), for example,
occurs, the cap discharges and smoothes out the dip making it less deep.
Same thing goes for the spikes.

The leads of the cap have to be as short as possible because at high
frequencies (noise for example) a wire no longer has negligible
inductance. (Inductance adds more fluctuation to the signal.) So the
shorter your capacitor leads are, the less inductance they have, the
greater the effect of the capacitor on smoothing the power and ground
signals.

HTH

Victor

P.S. You know, it is true: you have to teach someone a concept to be
sure you understand it.

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