Alt-BEAM Archive

Message #12393



To: beam@sgiblab.sgi.com
From: "sebastiaan van Vliet" sebastiaan_van_v@hotmail.com
Date: Thu, 23 Mar 2000 13:44:48 PST
Subject: [alt-beam] Allmost complete walker.



I've built the "allmost complete walker" design from Ian's page. How can i
turn the frequency down? I allready doubled all the cap's.

The schematic is great, good beginners stuff (like me). On Ians page there
is another schematic with two tactile sensors. How is that connected? what
are the "In's" for?
______________________________________________________



12394 Fri, 24 Mar 2000 10:03:53 +1200 [alt-beam] Logic puzzle - I need to built a new gate... :-) beam@corp.sgi.com Justin
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Hiya,
For the turning system of a walker I=92m designing, I ran into an engaging
logic problem that I thought I=92d share will you (mainly in the hope that
someone could solve it in a more elegant manner than I have :-).

The problem: (As illustrated below) I have a 4-state truth table and
want to build a circuit to give these outputs at the appropriate input.
It=92s easy if I use an XOR gate, but that would mean adding an entire
extra IC and I=92ll be trying to build small. My current solution when
freeformed would be slightly smaller than a chip, trouble is, it needs
adjusting when the voltage changes, and the voltage will change a lot
(solar walker) thus ruling out my design. I have no idea what the
circuit for an XOR gate is, and I think that could give someone who does
a big advantage.
The outputs are connected to the enable pins of a HC240, so that=92s the
kind of HIGH/LOW requirements the outputs have to meet.

If someone could see a way to fix the sensitivity of my circuit, that
would also be great :-)

Here is the guff:


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Attachment: puzzle1.gif

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12395 Fri, 24 Mar 2000 10:03:48 +1200 [alt-beam] A more efficient Solar PowerSmart Head beam@corp.sgi.com Justin
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Part of a solar walker I=92m designing involves the PS Head. I was looking
at two spare inverters on an HC240 that nothing would fit on (due to
needing to be on when the SE-driven enable would be off), and realised I
could use them on the PS Head. I think=85

Attached is the circuit showing what I thought off. I don=92t know enough
to know if it will work, but the idea is that when the SE switches off,
the inverters switch off, thus no matter how low the LDR resistance
falls, you=92re not losing any power across them.

So - whaddiya think? Would it work? Would it be better than not doing
this, given that I=92ll have the inverters just sitting there doing
nothing otherwise?


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12396 Thu, 23 Mar 2000 16:33:38 -0600 [alt-beam] Dumb newbie Q. beam@sgiblab.sgi.com CORBIT GIBERSON Before I really get goin I think I should get myself a multimeter. But
my experiance with electronics is nill ( in fact I think I'm pretty
dense) and I don't know what to look for in a multi, any help would be
greatly appreciated. I'd like something basic enough that I can jump
right in, but not so basic that as I improve I don't have to replace
it. Thanks all!
Corbit



12397 Thu, 23 Mar 2000 16:39:11 -0600 [alt-beam] Cricket beam@sgiblab.sgi.com CORBIT GIBERSON
I've got a schem. for a criket cricuit that uses a thermistor to
regulate the interval between chirps, the warmer it is, the more active
it is. If any ones interested let me know. (I'm not to sure how BEAMable
it is--it's made to run of a 9v supply)
Corbit



12398 Fri, 24 Mar 2000 10:00:50 +1100 (EST) [alt-beam] Re: Logic puzzle - I need to built a new gate... :-) beam@sgiblab.sgi.com Ben Hitchcock Hi,

Here a little bit of trickery I learnt at uni helps to solve the puzzle :)

Let's draw a map of inputs vs outputs for output 2.

S1 S2 out2

0 0 X
0 1 0
1 1 X
1 0 0

Since X menas irrelevant/not important, then we can just tie output 2
straight to ground! You can't get much simpler than that!

Now let's do the same for output 1:

S1 S2 out1

0 0 1
0 1 1
1 1 1
1 0 0

In other words, output 1 is S2 OR(NOT S1)

So here's the circuit: If S2 is high, output is high. Draw a diode from
S2 to the output.

If S1 is low, then output is high. Put a PNP transistor between Vcc and
output 1, with a base resistor that you think is about right going to S1.

Otherwise, it's a low.
Put a 100 k or so resistor between ouput 2 and ground.

Can anyone beat four components?

Ben

[Charset iso-8859-1 unsupported, filtering to ASCII...]
> Hiya,
> For the turning system of a walker I_m designing, I ran into an engaging
> logic problem that I thought I_d share will you (mainly in the hope that
> someone could solve it in a more elegant manner than I have :-).
>
> The problem: (As illustrated below) I have a 4-state truth table and
> want to build a circuit to give these outputs at the appropriate input.
> It_s easy if I use an XOR gate, but that would mean adding an entire
> extra IC and I_ll be trying to build small. My current solution when
> freeformed would be slightly smaller than a chip, trouble is, it needs
> adjusting when the voltage changes, and the voltage will change a lot
> (solar walker) thus ruling out my design. I have no idea what the
> circuit for an XOR gate is, and I think that could give someone who does
> a big advantage.
> The outputs are connected to the enable pins of a HC240, so that_s the
> kind of HIGH/LOW requirements the outputs have to meet.
>
> If someone could see a way to fix the sensitivity of my circuit, that
> would also be great :-)
>
> Here is the guff:

[image/gif is not supported, skipping...]


--
Nothing is foolproof to a sufficiently talented fool.



12399 Thu, 23 Mar 2000 18:00:33 EST [alt-beam] Re: Cricket beam@sgiblab.sgi.com Toby503@aol.com That sounds pretty cool. Could you send me the schematic?

Rusty Jones

email- toby503@aol.com



12400 Thu, 23 Mar 2000 15:24:23 -0800 [alt-beam] Re: Cricket beam@sgiblab.sgi.com Bruce Robinson CORBIT GIBERSON wrote:
>
> I've got a schem. for a criket cricuit that uses a thermistor to
> regulate the interval between chirps, the warmer it is, the more active
> it is.

Cool! Did you know that you can accurately tell the outdoor temperature
by timing cricket chirps? Unfortunately, I can't give you the formula,
because I was driving when I hear an entomolgist explaining it on the
radio.

Bruce



12401 Thu, 23 Mar 2000 18:25:15 EST [alt-beam] Re: Botic.com operational ! beam@sgiblab.sgi.com BUDSCOTT@aol.com Cool, i'll finally have a place to post a page!

-Spencer



12402 Thu, 23 Mar 2000 18:26:33 EST [alt-beam] Re: Allmost complete walker. beam@sgiblab.sgi.com BUDSCOTT@aol.com There are two resistors, both of which are 1.5M i believe, those hook up on
the side, they are red i believe, heighten the value to about 2.5 or 3, i had
the same problem with that circut!

-Spencer



12403 Thu, 23 Mar 100 23:23:01 GMT [alt-beam] re: Beam Motors beam@sgiblab.sgi.com cactus@dynamite.com.au Curiously, Timothy, I saw a tutorial on the web somewhere for building a walker
using a system like what you're describing. Cotton thread was used as a drive
belt and little pulley wheels were placed on the motor shafts. Sorry, I didn't
keep the URL. Frankly (no offence to whoever made the thing) it just didn't
look like something I was likely to ever want to try doing myself. I couldn't
imagine it working even half as well as the most rudimentary gearbox.

Dennison, Timothy is right about the availability of gear motors I'm afraid.
We aren't REALLY an industrialised society here (we just pretend). We export
primary products like wheat, wool, coal etc. and import manufactured goods from
Asia. Robot Oz doesn't seem to carry gearmotors and neither does anybody else,
although I'm sure you could get them by breaking open camcorders etc. There
probably is somewhere here that imports/makes gearmotors but they don't make
them available to the general public. With a population of 18 million there
just aren't that many people that want to buy half a dozen gear motors, so
nobody that has them sells them in small quantities.

Timothy, you have a couple of options. You could use servos. The cheapest
I've seen run at about A$25. Any model shop should have them, especially if
they sell remote control cars or planes. You can also order them from RobotOZ
or Oatley electronics. I think beam online has a tutorial on how to modify
them (you can't use them unmodified). There are many walkers made with servos
and they seem to work well.

Failing that, you could build your own gearbox or hack one from something
else. I just bought a kitchen timer from woolworths that has a very promising
gearbox inside it. The brand is "Propert" (an Australian tradition - you can
tell because it says so on the packet, just near where it says "made in China")
and its a 60 minute timer - looks like a white box with a dial on the front
that goes from zero to 60. You find them in the kitchen section and they cost
about A$5.50. A screwdriver is all you need to take the gearbox out and modify
it by removing some of the unneeded parts. The only thing I have to figure out
now is how to get the motor to mesh with the first gear. That shouldn't be too
hard, I have a few ideas.

Any clockwork object will have some kind of compliant gear box inside it (that
includes clockwork toys, though the gear boxes most likely won't be very
strong). You just need to find the one that works for you.

If you're really keen you can buy a set of plastic gears from Dick Smith and
build a gearbox from scratch.

Alternatively you can hunt around for things that might have good gearmotors in
them. Possibilities are: electric lens assemblies from camcorders or
autofocus cameras, ejector motors from Macintosh disc drives etc. You may be
able to get some of these things free from electronics repair places etc.

Happy hunting,
Cactus.

Dennison wrote:

Noo, you need gear motors. While I live very, very far away from Australia,
I do know for a fact there are gearmotors in autralia. To be perfectly
blunt, (and somewhat curiously) You couldn't be an industrialized society
without gearmotors. There are quite a few of them in Australia, as much as
anywhere else. You just aren't looking in the rigth places. Try robotoz or
other Australian robotics distributers.

dennison

Good Day,
I'm just enquiring about a method of operating legs on a beam walker.
Geared motors are not available here in Australia, and geararray's are way
expensive, I have hobby motors which are known to not have themselves, maybe
a rubber band joined to the shaft and to the legs, that work?? or another
suggestion?? Thanks to any correspondance.
Timothy
---
lee0-@eastloddp12.vic.edu.au
http://www.eastloddp12.vic.edu.au/


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