Alt-BEAM Archive
Message #08907
To: beam@sgiblab.sgi.com
From: "Ben Hitchcock" beh01@uow.edu.au
Date: Sat, 08 Jan 2000 12:41:21 +1100
Subject: [alt-beam] Re: Alf & Dragonfly
Hi,
>From: "Mike Kulesza"
> So I was looking at Ben's bots on his page just a moment ago...
>
> What are the specs on those solar cells you use Ben?
Hmmm - I'm not really sure. They cost $4 from my local department store,
and you get a free calculator with every one ;-)
> How is it that you only need 440 uF for the Dragonfly to flap its wings? Is
> it becaue the coils are so efficient?
Well, 440 uF gives a very nice solid flap for the coil that I used, so I
don't see the point of using a bigger storage cap. A bigger cap means more
off time - and I like to see my dragonfly flap as often as possible.
>You see, I use a 2433 cell on my
> magbot, and a 1000 uF cap. Under a 500 W halogen lamo it flaps like crazy -
> the clicking sound can keep up with a beat of most rock music. I know thats
> a weird thing to do with a magbot. Oh wel...
With mine, I had to eventually put a resistor in parallel with the coil. in
direct sunlight, the poor little thing couldn't dissipate the energy fast
enough. The wings were permanently held down by the coil!
It's funny, I gave this dragonfly to a friend, and he was quite happy to not
let the dragonfly out into the harsh sunlight because it couldn't cope. I
wanted to fix it so that it could cope, but he quite liked the idea that it
might be so fragile that it couldn't be out in the full sunlight!
The way it is set up the dragonfly will flap every ten seconds or so about
20 cm from a 60 Watt reading lamp. It belongs on a windowsill or desk near
a reading lamp. That's all the energy it needs.
>
> Are those normal yellow LEDs on Alf? Not photodiodes?
Ohhh yeah! Normal, run of the mill, rectangular LED's, the kind that light
up when you run 20 mA through them. I chopped them off a bit to improve the
photovoltaic effect, but they still work even unmodified.
The only reason I used LED's instead of phototransistors was size. I
couldn't find any rectangular PT's, but there were heaps of yellow LEDs in
my local Dick Smith.
If you are planning to copy the circuit, try clear LEDs as well. The kind
with a clear lens, not the kind give off white light. The red LEDs work
quite well, so long as they have a clear lens.
Cheers,
Ben Hitchcock
8908 Fri, 7 Jan 2000 17:53:02 -0800 [alt-beam] Re: SIMPLIFIED D1 CIRCUIT "'beam@sgiblab.sgi.com'" Wilf Rigter Hi Jim,
Just one solar cell is used both for charging and sensing in the SIMD1. It
is connected between 0V (neg) and the Schmitt trigger input (pos) and
through a diode to V+. When the solar cell output voltage drops 1/3 of the
voltage on the storage caps or battery. The Schmitt triggers and the SIMD1
output goes active high and can be used to control any other circuit. The
SIMD1 PNC example provides some positive feedback to clamp the solar cell by
loading it down. The diode in series with the 100 ohm resistor can be
replaced with a LED for a higher reset voltage.
Yes you can power boost 74HC14s the same way as HC240 by stacking them.
Connecting any number of HC gates in parallel, will multiply the available
output current by that number.
BTW I have tested an alternative SIMD1 circuit using an HC240 can be used to
control the remaining 6 inverters used for 3 bicores circuits which I will
post in a few hours. There are loads of other SE circuits which can be
adapted to the same D1 type single solar cell charging and "dark" sensing
configuration.
regards
wilf
> -----Original Message-----
> From: JVernonM@aol.com [SMTP:JVernonM@aol.com]
> Sent: Friday, January 07, 2000 4:36 PM
> To: beam@sgiblab.sgi.com
> Subject: Re: SIMPLIFIED D1 CIRCUIT
>
> In a message dated 1/7/00 3:56:24 PM Eastern Standard Time,
> Wilf.Rigter@powertech.bc.ca writes:
>
> > When the SIMD1 triggers at night, it snaps on
> > and the output signal can be used to control the 5 remaining 74HC14
> > inverters connected in parallel with the outputs used as a "power"
> switch.
> > Or the signal can be used as the tristate control of a HC240 or HC245
> or be
> > used as a PNC input for a microcore etc. to apply the stored energy to
> the
> > load.
> OK, I have a couple of questions Wilf. Does this circuit use two solar
> cells?
> One hooked to the +V and 0V connections and another for the switching
> function? Also, in your "power switch" configuration, would hooking all of
>
> the inverters in parallel add a power boost as it does with a single
> Bicore
> freeformed onto a single HC240?
>
> See ya,
> Jim
> http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
> ICQ# 55657870
8909 Fri, 7 Jan 2000 19:14:46 -0800 Re: Pressure Sensors beam@sgiblab.sgi.com Sathe Dilip Hi Wilf,
What you say is true & such a conductive rubber band will be ideal for
many applications. However I haven't come across any easy/cheap source
of such material. Once I was thinking about the antistatic mats. But
their conductivity is very low & sometimes the rubber material is bonded
to another cloth like layer. Do you know of something that will fit the
bill?
Meanwhile, the sandwich of a zebra strip (oriented properly) should work
better than the foam.
Dilip
-----------------------------------------------------------
Wilf Rigter wrote:
>
> Hi Sathe,
>
> The zebra strips do not conduct longitudinally (end to end) but only
conduct
> laterally (side to side) of the strip. But an all conductive elastomer
> "rubber band" would provide both spring action and a changing longitudinal
> resistance when stretched. This may make it suitable for use as tendons
> providing direct feedback of the longitudinal force and displacement.
SNIP
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