Alt-BEAM Archive
Message #08894
To: beam@sgiblab.sgi.com
From: Jonathan D Rogers chessmaster14@juno.com
Date: Fri, 7 Jan 2000 11:59:56 -0500
Subject: [alt-beam] Re: Pressure Sensors
Actually, Images Company(www.imagesco.com), which advertises in Robot
Science & Technology, has bend sensors for $10 each, and unlike Jameco,
no minimum order.
But I bet if you hunted about you could find some surplus for even
cheaper than that. All Electronics or Electronics Goldmine, for instance.
jonathan
8895 Fri, 07 Jan 2000 14:12:25 -0500 [alt-beam] Re: Pressure Sensors beam@sgiblab.sgi.com "Sathe Dilip" If crumbling of the foam & it's non elasticity are the main problems,
another thing that might work is a zebra strip. These are thin strips
of rubber (actually they use the term elastomer) with alternate black &
white stripes you may have seen providing connections between PCBs & an
LCD. The black stripes are conductive & the whole strip has excellent
elasticity. A construction similar to the foam sensor should work with
these strips as the sandwich material. Just a thought.
Also I don't remember where I read it, but the flex sensor
(Imesco/Jameco) was described by someone as changing resistance in steps
& not a continuous curve. If this is true, the robot might become jerky
in response too.
Dilip
------------------------------------------------------------------
Evaristo Westplate wrote:
>
> Hi,
>
> I used foam when I started with the biped and it works great except after a
> while the foam gets compressed due to the weight of the robot. We had to
> give the robot a break and get it of its feet in order to let the foam
> restore itself. We also looked at piezo sensors but they only give a
SNIP
--
Pl. remove *s from the e-mail address to reply
8896 Fri, 07 Jan 2000 20:21:24 CET [alt-beam] Re: events? beam@sgiblab.sgi.com "johannes urke" lucky you having beamers near you.
i live in norway you know and it looks like im the only beamer in the
coutry.
and your lucky to live in america at all if you got a map youll see that
norway is WAAAY up to the north pole!
those workshops... i heard something about one in summer.
i wanna go to one of those too:(
>From: "Mike Kulesza"
>Reply-To: beam@sgiblab.sgi.com
>To: beam@sgiblab.sgi.com
>Subject: Re: events?
>Date: Thu, 06 Jan 2000 23:19:31 GMT
>
>
>
>>hey guys are there any events around: from 23.5.2000 to about 18.7.2000?
>>(thats my summer vacation)
>
>Here in Canada, our summer vacation is from end of June to start of
>September. I doubt that ther is any other BEAM related events besides this
>and workshops... Too bad there's nothing ever in my area, in Ontario - but
>I
>know theres several BEAMers around here...
>
>______________________________________________________
>Get Your Private, Free Email at http://www.hotmail.com
>
______________________________________________________
8897 Fri, 07 Jan 2000 20:26:16 CET [alt-beam] Re: Pressure Sensors beam@sgiblab.sgi.com "johannes urke" what!! that stuff is conductive??
i gotta get it out of the thrash then.
>From: Gadagada@aol.com
>Reply-To: beam@sgiblab.sgi.com
>To: beam@sgiblab.sgi.com
>Subject: Re: Pressure Sensors
>Date: Thu, 6 Jan 2000 22:01:52 EST
>
>In a message dated 1/6/00 9:17:45 PM Eastern Standard Time, rix.g@bmts.com
>writes:
>
><< > Hi, I was just looking around for pressure sensors to use on my biped
> > walker. The first place I looked was Jameco and I found one that looked
> > good. I thought to myself "I'll get on the net and order 8 of them".
>That's
> > when I looked at the price and noticed that they were $10 each. No way
>I
> > could spend that much money. I then checked DigiKey. Prices there range
>from
> > $13 to $150. Ouch! I then checked that web site that Evaristo posted
>but I
> > couldn't find any prices on their site. Anyone know of a cheap source
>for
> > pressure sensors? Thanks
> Well, if you didn't mind some extra effort, you could attach a small gear
>to
> the end of a pot, and then use a rack (like in rack and pinion steering)
>to
> change the resistance. Just give it a spring to go back to normal, and
> voila! A pressure sensor (I hope). >>
>
>I remember reading in an old robotics book, maybe the "101 projects for
>robot
>hobbyist" or something like that, that a pressure sensor could be made at
>home using conductive foam, the stuff that IC's sometimes come with their
>pins stuck into. You simply attach a metal plate to either side of the
>foam,
>with connector wires attached to each plate. As the foam gets squeezed
>together, the resistance in the setup is decreased. Or something like
>that.
>
>
>
>Gary
______________________________________________________
8898 Fri, 7 Jan 2000 12:23:33 -0800 [alt-beam] Re: Pressure Sensors "'beam@sgiblab.sgi.com'" Wilf Rigter 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.
wilf
> -----Original Message-----
> From: Sathe Dilip [SMTP:sathe_dilip@bah.com]
> Sent: Friday, January 07, 2000 11:12 AM
> To: beam@sgiblab.sgi.com
> Subject: Re: Pressure Sensors
>
> If crumbling of the foam & it's non elasticity are the main problems,
> another thing that might work is a zebra strip. These are thin strips
> of rubber (actually they use the term elastomer) with alternate black &
> white stripes you may have seen providing connections between PCBs & an
> LCD. The black stripes are conductive & the whole strip has excellent
> elasticity. A construction similar to the foam sensor should work with
> these strips as the sandwich material. Just a thought.
>
> Also I don't remember where I read it, but the flex sensor
> (Imesco/Jameco) was described by someone as changing resistance in steps
> & not a continuous curve. If this is true, the robot might become jerky
> in response too.
>
> Dilip
> ------------------------------------------------------------------
>
> Evaristo Westplate wrote:
> >
> > Hi,
> >
> > I used foam when I started with the biped and it works great except
> after a
> > while the foam gets compressed due to the weight of the robot. We had to
> > give the robot a break and get it of its feet in order to let the foam
> > restore itself. We also looked at piezo sensors but they only give a
> SNIP
> --
> Pl. remove *s from the e-mail address to reply
8899 Fri, 7 Jan 2000 12:52:53 -0800 [alt-beam] Re: SIMPLIFIED D1 CIRCUIT "'beam@sgiblab.sgi.com'" Wilf Rigter
Yes,
Much it can be more efficient.
to quote Jim Mullins:
>The only problem that I anticipate is setting the
>"on" level of the D1. The range of coming on too
> soon versus not coming on fully is very small.
The original D1 using the 2N7000 gate threshold voltage as a detector gives
a "mushy" turn on point and no hysteresis and a significant amount of energy
wasted in the forward voltage drop when partially turned on.
Depending on the design, the 74HC14 leakage current near the threshold will
be reasonably small (of the order of the self discharge leakage rate of a
large super cap or battery). 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. An example circuit of a SIMD1 charger / "dark" triggered PNC for a
microcore is attached. Note the 100 ohm positive feedback resistor loading
the solar cell only after the SIMD1 turns on, can be adjusted to optimize
the SIMD1 turn off point. The output diode is connected in place of the
usual PNC in a microcore circuit.
regards
wilf
<> -----Original Message-----
> From: Bumper314@aol.com [SMTP:Bumper314@aol.com]
> Sent: Thursday, January 06, 2000 9:04 PM
> To: beam@sgiblab.sgi.com
> Subject: Re: SIMPLIFIED D1 CIRCUIT
>
[Wilf Rigter] ---8<---
>
> is this more efficient then the original D1
>
> Steve
Attachment: uSIMD1.gif
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