Alt-BEAM Archive

Message #08929



To: beam@sgiblab.sgi.com
From: "Ben Hitchcock" beh01@uow.edu.au
Date: Sun, 09 Jan 2000 12:05:13 +1100
Subject: [alt-beam] Re: Yo, Team!


Hi, wilf and all,

----------
>From: Wilf Rigter
>Date: Sun, 9 Jan 2000 4:35
> (c) The newer CMOS opamps can do practically everything and are "extreme"
> power misers to boot. (check Ben Hitchcock's Whistle Blower application for
> a 1uA oscillator at 9V which can't be done with any digital CMOS circuit I'm
> aware of)
>
> regards
>
> wilf

Just in case anyone is interested in the circuit and missed the URL, here it
is again:

http://wollongong.apana.org.au/~ben/elec250/

This has an index page with some cryptic links on it. The page with the
opamp circuit on it can be found by clicking on the link that says:
"Modified transmitter circuit".

Basically I had to make a project for uni that had to pulse a 300 MHz
transmitter once every five seconds. Since the battery used is one of those
little 12V batteries about half the size of an AAA, you need a pretty good
oscillator to do this without draining the battery away very quickly.

I used a TLC351 which, when operating, had an 8 uA standby current. The
lecturer wouldn't believe me when I told him that, he crossed it out of our
report and we lost marks for the value not being realistic. But then he was
the same lecturer who said that the transmitting aerial was too small to
transmit anything. "So what you're saying is that the remote control I have
been using for the past six months to get into my garage won't work because
the aerial is too small?"

Anyway, incompetence aside, this circuit goes to show that micro-power
opamps do work, and work very well. Wilf actually made a solar engine using
a micropower opamp, which I hope to try soon. If you want to find it,
search for uPOPSE on www.egroups.com, in the group alt-beam.

P.S. Yes, wilf, I am aware of the irony on my page where I say that opamps
can't be used for SE's! I'll fix it up soon.

Ben



8930 Sunday, 9 January 2000 7:27 photovore beam@sgiblab.sgi.com johannes urke
>hey guys i finally started making a photopopper photovore and when i had
>glued the transistors, 1381`s,the trimpot and the photodiodes together
>(usind chiu`s tutorial of course)i found out that the caps i had were 2.=
2uf
>not 0.22uf.
>now ill solder together the stuff i can without them,
>and when i get some caps there will be a mail with the subject: "why the
>#=A4@$ doesnt it work?" in your inbox so get ready to reply guys.
>
>______________________________________________________
>


8931 Sun, 09 Jan 2000 12:24:34 +1100 [alt-beam] Pressure transducers beam@sgiblab.sgi.com "Ben Hitchcock" One thing I haven't seen mentioned yet is a voltage divider idea.

I would imagine that a difference in pressure is far more valuable than
absolute pressure as far as balance is concerned, anyway.

Where I work, we use load cells to measure the load on various things (coal
bins, hot metal rollers, shears etc). These work by having an excitation
voltage, and a signal voltage.

It's a bit complicated to describe how they work, but applying the
technology to a BEAM foot is pretty easy:

Say you want to see what the difference in pressure is between two sides of
the foot, say left and right. What you do is make a voltage divider.

First of all, attach two foam pads to the foot, one on the left side, and
one on the right side.

Put two leads into each foam block, so now you can vary the resistance by
squashing the foam.

Put +5V onto one lead on the right hand side, connect the other lead on the
right hand side to a lead on the left hand side, and connect the last lead
(it should be one on the left hand side) to 0V.

To use it, simply measure the voltage on the lead that connects both the
blocks. 2.5 volts means that the pressure is equal, more means that you are
leaning to the right, less means you are leaning to the left.

This setup will be independant of the foam compressing over time (so long as
both sides compress equally), will be independant of the actual resistance
used and is about as simple a circuit as you can get.

Ben



8932 Sun, 09 Jan 2000 12:52:23 +1100 [alt-beam] Re: Alf & Dragonfly beam@sgiblab.sgi.com "Ben Hitchcock" Hi,

>From: Rob
>Date: Sat, 8 Jan 2000 19:24

> Ben,
> Do you find your Dragonflies lock up occasionally whether the blinking LED is
> covered or not? Any change in light gets them going again.
> Rob
>

Well, since I don't use a blinking LED at all, I can't really cover it up!
*chuckle* I used a SunEater circuit by Stephen Bolt. The schematic is at:
http://wollongong.apana.org.au/~ben/dragon/schematic.html

It's funny that you should mention this, however. I've been intrigued by
all this talk of FLED SE's and how you supposedly can't make a FLED SE using
pager motors, and can't have a FLED popper that uses one solar cell, etc.

Yesterday I made a photopopper using one solar cell, 2 pager motors and two
FLED solar engines. I managed to make it phototropic so that it circles
around underneath my reading lamp, but I'm not entirely happy with the
low-light performance. I'm in the process now of improving the circuit to
make it better in low-light conditions.

I've experienced the FLED lock-up problem, and I think it's because the FLED
pulls just a bit too much current for the solar cell to replenish, but just
not enough current to turn the transistors on. It's to do with the FLED
being supplied through the motor and the 2.2 k resistor.

I'll let everyone know if/when I make an improvement.

Ben



8933 Sun, 09 Jan 2000 13:24:46 +1100 [alt-beam] Re: Alf & Dragonfly beam@sgiblab.sgi.com Rob
Ben,

Well it still works beautifully the rest of the time despite the FLED. I haven't
been able to determine in some BEAM circuits online exactly which component is
used.
If you want to contribute another tutorial there seems to be an one missing on how
to go from a schematic to a rat's nest.
Rob
Ben Hitchcock wrote:

> > Ben,
> > Do you find your Dragonflies lock up occasionally whether the blinking LED is
> > covered or not?
> Well, since I don't use a blinking LED at all, I can't really cover it up!
> *chuckle* I used a SunEater circuit by Stephen Bolt. The schematic is at:
> http://wollongong.apana.org.au/~ben/dragon/schematic.html

Home