Alt-BEAM Archive
Message #00046
To: beam beam@corp.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Sat, 30 Jan 1999 22:05:06 -0600
Subject: [alt-beam] Re: New (feasible) photovore circuit?
Iave a giant solar panel that produces 9 volts @ 60 mA and wate to make a large
photovore, and for larger devices, where there is plenty of solar panel and
motor size, this may infact be better than the traditional SE! I'd like to try
it out! This realy isn't an SE, in that it doesn't appear to have any form of
storage, but it's probably possible to add it. is might be good for the idea of
a battery based system, or maybe one that stops and charges, then runs a while.
Doesn't look to hard. Anyone got a charge, run type circuit?
Victor Snesarev wrote:
>
> Below is a circuit and a description of possible photovore. Since I have
> not built this circuit yet, I cannot be sure that it works, but the
> theory seems ok to me. I would appreciate any comments or suggestions
> that you might have.
>
> Also, I sending this message as text, and if viewed with fixed width
> font the schematic below should have correct proportions. I also put the
> schematic in graphics on my WWW site
> (http://www.eel.ufl.edu/~vsn/photovore_circuit.html).
>
> (+) (+)
> | |
> | ----[MR]----
> | |
> - /C
> RR ----[R1]----| B Q1
> - | \E
> | | |
> | N1 | (gnd)
> |-------[>o-----|
> | | (+)
> | | |
> - | /E
> RL ----[R2]----| B Q2
> - \C
> | |
> | ----[ML]----
> | |
> (gnd) (gnd)
>
> RR & RL = Photoresistors (CdS) right and left
> N1 = 74HC14 (Inverter with Schmitt-trigger input)
> R1 & R2 = 1k transistor bias resistors
> Q1 = NPN transistor (2N2222 for example)
> Q2 = PNP transistor (2N3906 for example)
> MR & ML = motors
>
> Circuit operation (at least how I expect it to work):
>
> Photoresistors (devices that change resistance in proportion to light
> intensity. More light = less resistance.) form a voltage divider. The
> voltage is "sensed" by the schmitt-triggered inverter which, depending
> on the difference between the voltage dropped by RR & RL, would output
> either a 1(+) or a 0(gnd).
>
> When the light source is left of the direction faced by the bot RL is
> lower than RR, so the voltage at the input of the inverter drops. The
> inverter output goes high. Q1 turns on. MR runs (ML doesn't run), and
> the bot turns left around the left motor.
>
> Opposite happens if the light source is to the right of the bot.
>
> If the light source is straight in front of the bot, and both CdS get
> the same amount of light, due to hesterisis (schmitt-trigger) the bot
> will turn in whatever direction it was turning before it was facing the
> light source (before entering the threshold region of the trigger). Once
> it turns far enough to cause the inverter input voltage to go above or
> below the schmitt-trigger threshold, it will turn in the other
> direction.
>
> I am not sure what to call the forward movement of such a creature, but
> it's almost like a walking gate (or is it just wishful thinking on my
> part?). A wide wheel base would be advantageous in this design.
>
> I should also say, that I realize that the design is not very efficient.
> The inverter would keep switching, and doesn't CMOS need more current
> for switching then driving a constant voltage? Also, below 2V (lowest
> operational voltage of CMOS) the inverter would not work.
>
> Anyway, please let me know if you think this might work and include any
> other comments.
>
> Victor
--
Richard Piotter
richfile@rconnect.com
The Richfiles TI Hardware and BASIC web page:
http://www.geocities.com/SiliconValley/Lakes/5081/Richfiles.html
------------------------------------------------------------------------
eGroup home: http://www.eGroups.com/list/alt-beam
Free Web-based e-mail groups by eGroups.com
Home