Alt-BEAM Archive
Message #08590
To: beam@sgiblab.sgi.com
From: jester96beam@iname.com
Date: Fri, 24 Dec 1999 12:14:34 -0500 (EST)
Subject: [alt-beam] Re: 4 motor walkers
It may have more functionality, but it is an 8 motor walker, where as Dave's is a 4 motor. Dave's kits are of VERY high quakity. I haven't ordered Lynxmotion kits before, but they don't look any better than Dave's, just different.
Anyway nobody has really answered my original questions yet. How do you make a 4 motor walker turn or reverse? I just want to know if it's as simple as reversing one (or 2?) motors as in 2 and 3 motor walkers or what?. And to turn them do you do the same as 2 motor walkers, or adjust the gate of the front (or back) TWO motors or something else?
Chris
---- you wrote:
> In a message dated 12/23/99 7:07:38 PM Eastern Standard Time,
> jester96beam@iname.com writes:
>
> > What about Scout Walker 2? I found a few sites with good info on it earlier
> > today. They say it does a fairly good job of getting around. It's motors
> are
> > mounted differently, so what about it?
> If you mean the Solarbotics kit, I'd have to say it doesn't compare to the
> Quad walker at Lynxmotion. This is just my opinion based on the options and
> expandability of the Lynxmotion product and is not a knock to Dave (although
> it will be seen that way no matter what). Particularly if you compare
> functionality to price. If this offends anyone's sensibilities, please,
> imagine that I said Scoutwalkers are wonderful, beautiful, robotic platforms
> destined to revolutionize robotics as we know it. And also, please everyone
> go out and buy at least 6 of them.
>
> See ya,
> Jim
> http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
> ICQ# 55657870
>
---------------------------------------------------
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8591 Fri, 24 Dec 1999 09:44:59 -0800 [alt-beam] Re: LEDs "'beam@sgiblab.sgi.com'" Wilf Rigter Hi Mike,
The forward voltage (Vf) of LEDs is all over the place depending on color,
semiconductor material and structure, temperature and current. The standard
GaAs IR and Red LEDs have the lowest and flattest voltage curves so are
probably better suited for low current "zener reference" applications. Most
IR and some standard GaAs red LEDs can be used in single battery (1.5V)
circuits. High efficiency LED applications require a 2 cell supply. Green
and Yellow LEDs are usually 10% higher Vf than equivalent Red LEDs.
Here is my rule of thumb:
At a 20mA forward current:
GaAs IR LEDs used in TV remotes, slotted detectors typ Vf = 1.2V
GaAs standard Red LED visible low efficiency) typ Vf = 1.5V
GaAsP or AlGaAs visible high efficiency, any color LEDs typ Vf = 2.0-3.0V
A few LEDs have 2 chips in series which doubles the Vf.
At low forward currents (10uA-1mA) for voltage reference or zener
applications, LEDs Vf is about 80% of Vf @ 20mA. At very low <1uA forward
currents the photovoltaic voltage can dominate unless the LED is covered.
An FLED is a LED with build-in flasher IC which has very low leakage current
while OFF and which does not turn ON until the voltage across the FLED
reaches the lowest operating voltage. The FLED is normally used for flashing
indication with a constant supply voltage but for FLED SEs, the supply
voltage slowly rises while the solar cell charges the supply capacitor,
until it reaches the minimum operating voltage of the FLED which then turns
on to trigger the SE latch and motor driver dumping the stored solar energy
through the motor.
hope this helps
wilf
> -----Original Message-----
> From: Mike Kulesza [SMTP:mikekulesza@hotmail.com]
> Sent: Thursday, December 23, 1999 6:01 PM
> To: beam@sgiblab.sgi.com
> Subject: Re: LEDs
>
> What about the colours on normal LEDs? what are the voltages?
>
>
> >From: Dave Hrynkiw
> >Reply-To: beam@sgiblab.sgi.com
> >To: beam@sgiblab.sgi.com
> >Subject: Re: LEDs
> >Date: Thu, 23 Dec 1999 18:36:26 -0700
> >
> >At 06:00 PM 12/23/99 , Mike Kulesza wrote:
> >>So how do all these different kinds of LEDs effect the SE anyway? Why
> does
> >>the FLEDSE use a FLED? not say some other type? What do the colours
> mean?
> >>--> trigger voltage? What does whether it flashes or not mean?
> >
> >FLED = FLASHING LED. Pretty much a necessity, although you can get away
> >with regular LED's as triggers if you've got enough solarcell.
> >
> >FLED colour DOES affect trigger voltage. Green is the lowest (going from
> >memory here...), triggering at about 2.8V. Yellow triggers at about 3,
> and
> >Red is highest at 3.4V, but these are dependant on the FLED manufacturer
> >too.
> >
> >Regards,
> >Dave
> >---------------------------------------------------------------
> >"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
> >that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
> > 2 vowels. Pronounciation? _SMITH_".
> > http://www.solarbotics.com
>
> ______________________________________________________
>
8592 Fri, 24 Dec 1999 20:33:07 -0800 Re: Carbon fiber, very dangerous and construction overkill
>
>
>
> re the recent chat on carbon fibre
> as I pointed out before carbon fibre splinters dont tend to be visible to
the
> naked eye and once in your skin migrate around your body,
> the recomendation is that when handling the raw cloth or strand rubber or
latex
> gloves are worn,
> when cutting the stuff as some have described large coluds of the stuff
become
> airborne so when cutting rod lubricate with washing up liquid (soap) that
way
> you will keep down the stuff , NEVER NEVER NEVER sand the stuff without
a
> wetting medium.
>
> The use of carbon in our context is downright stupid since its just
overkill for
> the task, I remember the chaps that made a walker in 1/8 th carbon sheet
!!
> they dont even use stuff that sort of sheet dimension often aircraft let
alone a
> mincing little bot. These fools apparently sanded the stuff to shape
!!!!!!
>
> This stuff is only of any value if you use it in the correct places for
the
> right reason rather than for the sake of using it !!!!!
> Remember that Carbon Fibre is stiff but britle and in rod form the resin
that
> surrounds the inividual fibres will delaminate from the fibres long before
the
> actual fibre snaps.
> I recomend that beamers stick to safer alternatives that are plenty
strong
> enough for our task unless you know the PROS and CONS of Carbon,
> have a valid reason to use it ,
> and intent to use it in sensible construction techniques.
>
>
> Rob D
> AKA " Powerbuilder"
>
>
>
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