Alt-BEAM Archive
Message #03809
To: beam@corp.sgi.com
From: Don Papp donp@cronus.oanet.com
Date: Thu, 27 May 1999 18:10:38 -0600 (MDT)
Subject: [alt-beam] Re: Heads
On Thu, 27 May 1999, Keagan Schpfer wrote:
> 1) do you have to use gear motors. could you just use normal motors.
You *could*, but it won't work as expected. The gears provide
the torque ('power') to move the head, whose weight may or may not be a
problem - depending on how you built it.
But, assuming the motor is able to move the head without the
benefit of gears, a plain jane motor will usually cause problems by a)
moving too fast (gears slow them down), and b) not being able to 'hold'
their last position well (if at all) when not under power.
Finally, a motor doing work without the advantage of being geared
will consume more power. (A big concern when using solar power)
> 2) is it possible to use CDS cells instead of photodiodes if you put them
> parallel with a regular diode? or, do you even need the diode.
People have made alternate designs using cds cells. I believe Ian
B has done so - though not necessarily with a head. Check
www.beam-online.com for his site.
However, to answer the implied question - No. A cds cell with a
diode is not the same as a photodiode and will not act the same. A cds
cell and photodiode both are influcenced by light levels, but they don't
work the same.
> 3) is there such a thing as a Z bridge head? i know that dave from
> solarbotics made a head of some sort of a bridge, but i can't remember the
> name. does any one have the circut for this bridge???
I made a head using a Z bridge, so yes. I'm not sure this is what
you're asking though. The Z-bridge (schematic on the BEAM Tek faq, should
be a link from beam-online at least) is just a motor driver. The head I
made has 2 suspended bicores driving the motors through a Z-bridge.
(total of 4 photodiodes for the 'eyes')
> 4) is the best power source batteries? how effective are solar powered
> heads?
You can do either. A battery-powered head is more active, as it
moves pretty much all the time. A solar powered head will work more like
a sunflower. (ie slower but self-contained and will never run out of
power as long as there is light) May be a bit like watching the minute
hand on a grandfather clock, though.
> oh yeah, i am building a herbie, and i was wondering what kind of a
> body/frame i should use.
The components themselves can be the 'frame' if you freeform, or
you can use something light like paperclips or light gauge (but not too
light) copper wire if you have it available. Check some beam sites and
pictures out to see how others build their bots, then steal the best
ideas. :)
| Donald Papp, T.T., MCP
| Support Analyst
| OA Internet Inc.
| don@oa.net
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