Subject: [TCRG] A good RSOH last night.
Date: Sat, 15 Sep 2001 21:50:50 -0500 (CDT)
From: Alan Kilian
To: tcrobots@orbis.net (Twin Cities Robots Group)
Jeff S, Ron and I had a good time at last night's RSOH.
I am working on solving a problem at the Neuro-behavioral lab
at the U where they were seeing some noise mixed in the signals
coming from people's brains, and I THINK I FIGURED IT OUT!!!
After several weeks of experiments, I think the last of the
noise was coming from a 12 Volt DC power supply in the amplifier
rack. This will make a great story once we have run for a few
weeks, and can be sure that the noise is gone, and that it wasn't
caused by the PET scan van outside the building, and that it will be
back when the van returns. I'll write the story up sometime, and post it.
It was a great investigative/political/social/engineering problem.
An order from www.meci.com arrived. A two-motor/clutch assembly for use
with a bicycle to make an electric bicycle. I'm using it on Scooter-II
$40.00
Two 17 Amp-Hour sealed lead-acid batteries $20 each
Three 24-Volt chargers $20.00 each
I think the chargers look VERY nice. They switch from 30 Volts back to
28 Volts as the battery becomes completely charged. You can see two
LEDs blink back and forth when the battery is mostly charged.
I'll let you know if they really work in a few weeks.
I think the battery price is good also if they turn out to be good
batteries. I charged overnight, and now I'm discharging through a
100 Watt house light bulb at 0.350 Amps, so it will take 48 Hours
or so to discharge. I'm recording loaded Voltage, Unloaded Voltage,
Current and individual battery voltages as it discharges.
These are going to be the scooter batteries.
So for about $150 you can build a scooter yourself. Motor, batteries,
charger you can build a scooter yourself. Motor, batteries, charger
and a $50 scooter from Toys-R-Us.
Ron had some code for a PIC12C509A to act as a speed controller for a
model airplane motor, so we used one of my $0.93 processors, wired
it into an 8-Pin DIP socket, and programmed it. It works!!! You can
move the radio control transmitter stick, and the thing produces
a PWM output. We had an LED hooked up as a test, and it's brightness
changed. This thing even has a "brake" output to short out the motor,
and stop the propeller.
We hooked up a geophone to the sound card input of my Linux box, but
didn't get it to work. Then we went to a Windows box, and got it
working. We stomped around, held it up to our throat, and sang, and
generally had a good time with it. Purely in the pursuit of further
understanding of some science thing I assure you.
Then we went to Perking at 1:30 to eat and listen to some drunk people.
3:30, and it was time for bed.
And Jeff's transmission didn't leak TOO much fluid on my driveway!
-Alan
Subject: [TCRG] meci.com 24 Volt chargers.
Date: Sun, 16 Sep 2001 19:38:25 -0500 (CDT)
From: Alan Kilian
To: tcrobots@orbis.net (Twin Cities Robots group)
I think that these meci 24 Volt lead acid chargers are a good deal
at $18 each. ($20 and a 10% online discount)
It looks like they are a constant-voltage charger set at 2.55 Volts-
per-cell which is exactly what the "battery bible" says to use for
maximum number of cycles.
It does mean that it takes a fair amount of time to charge.
I am getting about 3 Amps out of the charger at the beginning, and
then after about two hours, it shifts into a pulse-at-a-time mode
where it hits the battery with 30 Volts, and then idles while the
battery falls to about 28.6 Volts, then it hits it again.
I think it should charge a 17 Amp-Hour battery overnight from 100%
dead. That's good enough for me. It will probably get a 100% dead
17 Amp-Hour battery 70% charged in 8 hours.
It's the switch from constant-voltage to this pulse thing that
makes it take longer than you would expect, but that's also a
good way to make sure that the batteries don't get overcharged.
I think it will be perfect for the scooter.
-Alan
"Battery bible" = _Handbook of batteries_ 2nd Edition David Linden
Editor McGraw-Hill 1995 ISBN 0-07-037921-1 $125 at amazon.com
