Alt-BEAM Archive
Message #01827
To: jason - evenflow88@hotmail.com, beam beam@corp.sgi.com
From: Sean Rigter rigter@cafe.net
Date: Sun, 28 Mar 1999 17:00:02 -0800
Subject: [alt-beam] Re: FLED misery
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The jig is up mR.jason. Great fun!
Sounds like you would make a good target for my new uPOPSE design
attached.
jason - wrote:
>
> hie do u have any ideass how i could contact mR.scott martin the guy who
> built komodo dragon...cause i want to ask him a lil bout his FLED
>
Hello beamers,
Here is a micro power (5uA) version of the ever popular solar engine.
The micro Power OPamp Solar Engine (uPOPSE) is designed for 5V-12V
applications perhaps using the LEGO motors recently mentioned. It should
work well with BG Micro and other lens motors. I tested this design with
a couple of Sony lens motors. The circuit uses small power mosfets and a
dual cmos opamp (TLC27L2) made by TI (Cdn$1.25). Similar CMOS opamps and
larger mosfets should also work. The photo diodes are generic (5 for
Cdn $1.99) with build-in IR lens. They are moderately sensitive : with a
20W halogen light 6 inch away and a 5V bias the leakage current is 500
uA and in normal ambient light I read about 5 uA. The lenses of the PDs
seem to integrate light omni directionally although the front is twice
as sensitive as the back or the top. With components shown, the
circuit draws a constant current of about 5uA By adding Green or Red
LEDs in series with the existing green LED the threshold can be raised
to 8V or 12V. The cut-off voltage is about 3V which is the voltage
(Vgs) at which FETs come out of saturation. The Rds of the BS170 is
about 4 ohm with >3V at the gate and lower Rds FETs may be substituted
for higher motor current loads.
The size of the capacitor can be reduced at the higher voltage, my lens
motors start turning over with a 220 uF @ 4V charge. This is because
the energy stored in the cap is proportional to the square of the
voltage so 4700uF/2V is (approximately) equal in energy to 330uF/8V.
Since many caps which are used for these application are the common 10V
or 16V rated variety, there is some untapped potential in terms of the
maximum energy that can be stored in these capacitors. To make efficient
use of the energy at higher voltage you must find a suitable
(efficient) motor designed for 6V or 9V use. I believe many camcorder
lens motors are 6V or 7.2V and may be good candidates. You will have to
use solar cells in series to generate the higher voltage output but
charging time should be about the same for a given energy whether you
use the smaller cap and series panels or larger cap and parallel panels.
Forward voltage drops in switching devices are somewhat less of a
concern at 9V compared to 2V applications since for equivalent power
higher voltage rated motors, the winding impedance is higher and motor
currents are lower.
In a nutshell (am I dating myself here?), the micro Power OPamp Solar
Engine (uPOPSE) works as follows:
The basic circuit a threshold detector with hysteresis: the opamp output
switches positive and turns on the FET when the (+) input is more
positive than the (-) input (threshold) . When the FET turns on the (-)
input is pulled to the 0V line reinforcing the difference between the
(+) and (-) inputs (hysteresis) . This is the same principle used in the
Schmitt trigger and most solar engine designs which use transistors or
CMOS inverters as ( not so low power) opamps.
The design is by no means optimized but it is free and unencumbered and
I invite everyone to help themselves to make improvements. A 3V version
is on the drawing board. I just hope it will not be considered "too
linear" for BEAM land 8^)
enjoy
wilf
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1828 Sun, 28 Mar 1999 20:22:50 -0500 (EST) [alt-beam] Re: Personality Bruce Robinson DENNLILL I actually tend to agree. I mean I know I'm not so uptight about my
personal stuff but I do see the nature of the beast here. It's not like
the message was just "My Names dennison, I'm a professeor at such and such
university. I've written these books, e-mail me at blahblah@blah.com"
These messages are more like "I like this and do this, and this". So yes,
I would agree. There should be a curt listing of people, but perhaps just
name and e-mail, web site and some particular claim to fame (like a
particular bot or somehting) Other than that, lets keep this off web
pages.
Dennison
On Sun, 28 Mar 1999, Bruce Robinson wrote:
> Richard Caudle wrote:
>
> > What is going to be done with the "personality" posts? Are they going
> > to be assembled into a Rogues' Gallery or something of that sort?
>
> Hmm? Is this appropriate? Will's original posting was more along the
> lines of. "Let's introduce ourselves". No mention about hanging
> everyone's personal details out for the world to see.
>
> There are 400 people on the list, more or less. Only 27 have sent in
> bios in response to this suggestion. Could it be the remaining 93% held
> off because they were afraid this might happen? What does everyone else
> think?
>
> I've got enough disk space to keep the notes on my PC, for my eyes only.
>
> Regards,
> Bruce
>
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