Chip with simple program for Toy

[Phil Allison]

"Sjouke Burry"

http://i360.photobucket.com/albums/oo48/ron08840/000_0003.jpg

The top part is a very nice signal generator,

** You nuts ??

The top unit is a simple DC volt and DC mA meter.

the lower part is an ac/dc voltage supply, unclear what frequency
the AC setting supplies.

** Mains frequency, of course.

It can apparently also act as a variable resistor,

** Huh ?????

How many fairies have you been chasing lately ??

The two analog meters give a nice display of the selected output range.

** They BOTH read incoming DC voltages and mA.

The VOM one will additionally read AC volts and mA plus resistor values -
with low accuracy compared with even a very cheap DMM.

If it works correctly, you have a very nice piece of equipment, with
extremely high output ranges in voltage and current.

** Utter nonsense.

The max AC is 40 volts and the max DC is 20 volts.

It is designed to be safe for novice, teenage students to use.



....... Phil

 

[Phil Allison]

"Sjouke Burry"

John Popelish wrote:

No. That section is an amp/volt meter that goes up to 200V /2A.

The top part is marked as a signal generator

** No it is NOT !!

It is clearly marked as a " DC Meter ".

Are you sure you are not just seeing a volt ohm meter? That is what I
see.

The bottom part is marked as AC/DC supply.

** Huh ??

Totally off with the garden fairies.

So I advise you to re-examen the last picture.

** I advise you get your eyes and head examined.



...... Phil

 

[Phil Allison]

"Peter Bennett"
rjv494@verizon.net

http://img504.imageshack.us/img504/6294/0000003hx4.th.jpg

A decent-sized picture rather than that thumbnail

** Been posted long ago.

Any maker's names,

** The name is in the heading " Lab-Volt "

http://www.labvolt.com/


The OP's unit look like something they produced for electronics students 30+
years ago.



...... Phil

 

[Rob Dekker]

"John Bailey" <john_bailey@rochester.rr.com> wrote in message news:ks8vc49rhpdt6hhtrenrb3nsrvos723lpp@4ax.com...

On Mon, 15 Sep 2008 12:49:22 -0700 (PDT), Bret Cahill
BretCahill@aol.com> wrote:

The pursuit of a "super" battery that could cheaply and efficiently
store energy all at a high density might not be the best use of time
and resources.

A more plausible solution would be a system of several different
batteries with an electronic controller which would charge and
discharge the various batteries depending on the source of power.

Include capacitive storage in your selection and you may have a
winner. Especially with regenerative braking as a power source. The
charging rate needed to transform kinetic energy into a stored form is
higher than most batteries can efficiently accept.
Recovery efficiency estimates range from 20% to 40%. The extra weight,
cost and complexity of redundant storage may be justified.

I think your numbers are outdated.
Modern systems can recover more than 80% of the kinetic energy during regenerative braking.
PML's Hi-Pa drive gets even 85% back :
http://www.pmlflightlink.com/motors/hipa_faq.html
Quote from this page :
"The Super capacitors are sized to hold the full energy of the vehicle kinetic energy at 70mph. This is around 700kj. So as the
vehicle speed increases we maintain "space" in the capacitors to absorb the regenerated energy from braking to stop from this speed.
Note that the regenerative braking captures about 85% of the available kinetic energy from the vehicle motion. This means that you
no longer need feel guilty about the amount of fuel burned when accelerating fast from the traffic lights! Most of the energy used
to perform this acceleration will be recovered when you stop!"

Simply charging a capacitor without large resistive losses is a
problem. Possibly this can be solved with clever switching of an
inductor but this is not obvious.

True, and the opposite problem occurs when you want to pull the supercapacitor empty when you are accellerating.
Yes, there is a inductor involved. In home-built electric vehicles this is often an aluminum coil.
But the switching part is easy : high-power electronics are marvels these days in solving the differences between power requirements
and capacitor charge level at very high efficiency rates.

Rob

 

[hanson]

"Rob Dekker" <rob # verific.com> wrote
http://groups.google.com/group/sci.chem/msg/3b40a7e5c2b19b0d?hl=en
[snipped non-germane lamentations]
recycling alone will not solve the looming Lithium shortage
once we start using Lithium batteries for PHEVs and EVs.
Here is a report (thank you B. Richardson for the link)
which outlines the supply constraints on Lithium :
http://www.evworld.com/library/lithium_shortage.pdf &
http://www.meridian-int-res.com/Projects/Lithium_Microscope.pdf

hanson wrote:

Of course, any and all recycling has always been done
when it was/is and will be commercially economical
and profitable. --- ----- ------ --- No Green shit advice
is required for that.... ahahaha... Of course, the green
turds had to muzzle in & charge waste re-processing
fees & recycling-permit charges on the OEM, the user
and the recyuler... all counter productive taxes that are
possible cuz or the hordes of little Green idiots who
are the witless & unpaid enablers and facilitators for
the Green Sharpies who fucke'm like Hogan's goat....
ahahaha...
There's no difference between Oil hogs & Green shits.

Now, in classical green fashion, you naturally have not

recognized that your looming Lithium shortage is largely
artificial and simply engineered by speculators for the
investors in that Li market... done along the very same
recipe by which the oil bois are fucking us a the pump....

The same gig, but much more serious is the Copper

issue precipitated by the coming mass introduction
of electric cars and the revamping and expansion of
the power grind... --- --- 3 weeks ago the Chairman of
the largest Copper/mining producer was on TV and
said what I just mentioned and added... "Come on in
folks!. Sink your investments into copper... for we are
running at capacity now and we have NOT found any
new untapped Copper ore deposits, anywhere on the
globe, despite looking for them for the last 20 years"...

Thanks for the laughs.. Your Green chicken are coming

home to roost.... ahahhaha.... ahahahanson

 

[Phil Allison]

equal105@gmail.com
"Phil Allison"

** The name is in the heading " Lab-Volt "

http://www.labvolt.com/

The OP's unit look like something they produced for electronics students
30+
years ago.

http://www.labvolt.com/products/electricity-and-electronics/instrumentation/laboratory-instrumentation-system-438

This device's design is indeed very old, but it's still being produced
and sold.

** Amazing something so obsolete is still available.


It is intended for students and novices, not for professionals
or serious hobbyists.


** Like I commented.


I used to work at Lab-Volt and I've tested or
fixed a few of these...
If you could see how this thing is made inside it would feel like
making a time travel some 25 years back.


** Only back to 1983 ?


There's a link for the datasheet on the page.


** Can you give the OP an idea of its value then ?



...... Phil

 

[christofire]

"davidd31415" <davidd31415@yahoo.com> wrote in message
news:1cefa215-e28d-47b4-9ca4-7fe9811b6f19@y38g2000hsy.googlegroups.com...

I'd appreciate some help with this equation... I've been looking at it
for a few days now...

Here's the equation:

http://img367.imageshack.us/img367/1222/...

I'm trying to understand how the formula for the phase angle is
determined.


Thanks for any help.

Link doesn't work for me.

Chris

 

[christofire]

"davidd31415" <davidd31415@yahoo.com> wrote in message
news:fe7bc8b6-37d6-4f6b-8bd5-d7cca9ebc7a9@m45g2000hsb.googlegroups.com...
On Sep 17, 8:53 am, "christofire" <christof...@btinternet.com> wrote:

"davidd31415" <davidd31...@yahoo.com> wrote in message

news:1cefa215-e28d-47b4-9ca4-7fe9811b6f19@y38g2000hsy.googlegroups.com...

I'd appreciate some help with this equation... I've been looking at it
for a few days now...

Here's the equation:

http://img367.imageshack.us/img367/1222/...

I'm trying to understand how the formula for the phase angle is
determined.

Thanks for any help.

Link doesn't work for me.

Chris

My mistake. Correct link:

http://img367.imageshack.us/img367/1222/img7229xj0.jpg


Take a look at the relevant page in Wolfram Mathworld, titled 'Complex
Argument' at:

http://mathworld.wolfram.com/ComplexArgument.html

The 'argument' is what you've called the 'phase angle' and it is shown how
the argument of the product of several complex numbers is found by adding
the arguments of the individual complex numbers. Consequently, for your
case, the argument of one complex number divided by another can be found by
subtracting the argument of the divisor from that of the numerator.

Does this help? Is your working, on the page to which you linked, correct?

Chris

 

[David Bostwick]

In article <pan.2008.09.17.19.08.36.182504@example.net>, Richard The Dreaded Libertarian <null@example.net> wrote:

On Mon, 15 Sep 2008 16:09:48 -0700, Uncle Al wrote:

We know to the gallon how much gasoline is burned in Southern California -
it's taxed. We know the efficiency of an IC engine. We know the
efficiency of an electric motor. We know battery charging, storage, and
use effciencies. We know how many kW-hr replace that gasoline. We know
what demand brings the grid down on hot summer days.

Run the numbers, then apologize.

Hey, I've got an idea! Why don't you run your _own_ numbers, and show us?

Thanks,
Rich

Burden of proof is on those who want to change things.

 

[Jerry]

"Dave, I can't do that" <davenpete@gmail.com> wrote in news:a08a31d0-129e-
446d-a507-529a30e0cb81@z6g2000pre.googlegroups.com:

http://www.electronickits.com/kit/complete/motor/ck1400.pdf

Try this; http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm

 

[Bob Masta]

On Wed, 17 Sep 2008 14:52:47 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com>
wrote:

On Wed, 17 Sep 2008 13:11:06 -0700 (PDT), "jalbers@bsu.edu"
jalbers@bsu.edu> wrote:

From my reading about electronics, I have been made aware that
resistors are sources for noise in circuits. It is kind of a downer
finding out that a very basic building block (the resistor) will
probably be a source for trouble later on if I was ever to get really
serious about amplifier design. Right now, I am at the crawling
stage. I want to do some of my own experiments and have some very
elementary questions.

1. In a simple DC circuit (stable power source, and carbon resistor
for example), will the resistor create noise? Looking at the fromula
Vrms = SQRT[4KRTB] where B is the bandwidth, since it is DC would the
B=0 making Vrms = 0?

Resistors make Johnson noise, per the formula, with no DC bias ("power
source") present. And yes, if the measurement bandwidth is zero, the
noise is zero. But it will take literally forever to make the
measurement.

To clarify, B is the *measurement* bandwidth. This
has nothing to do with the fact that you applied
DC to the resistor. The resistor generates noise
at all frequencies, and the more frequencies you
include in the measurement (larger B) the larger
the total noise will be.

If you are using the resistor in an audio circuit,
then you'd probably want D to be something like
20000 Hz to cover the audible range. (In a real
audio device like a preamp, you might also want to
include a "weighting curve" to attempt to adjust
for the fact that our ears don't hear all
frequencies with equal efficiency. The curve you
see mentioned most often is "A weighting". It
actually isn't very good for the job, but it has
become a de-facto standard.)

Hope this helps!


Bob Masta

DAQARTA v4.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!

 

[Paul E. Schoen]

"Dave, I can't do that" <davenpete@gmail.com> wrote in message
news:a08a31d0-129e-446d-a507-529a30e0cb81@z6g2000pre.googlegroups.com...

Hi,

The following is a PDF of a motor control kit...

http://www.electronickits.com/kit/complete/motor/ck1400.pdf

Currently it is designed to run at around 410Hz.

I assume that too will be the frequency for the PWM output but I need
5KHz from the PWM.

I looked at the formula for frequency on page 1 and it may as well be
written on Chinese as far as I can tell.

Could someone with a brain significantly superior to mine, please tell
me what components need to be changed to get this to operate at 5Kz. I
need this to operate at 5KHz, 5volts and 100mA PWM output from 0%-95%

Thanks so much.

This would be very easy to implement with a PIC, but then you would need to
learn how to program using PIC code, which is not all that simple.
Microchip has an app note for motor control using a PIC16F684, which I have
used for a step-up DC-DC boost converter. The document shows the schematic
and basic operation of a motor control kit which I got as a prize at a
Microchip seminar. You can have a look at:
http://ww1.microchip.com/downloads/en/AppNotes/00893a.pdf

Another good app note is:
http://ww1.microchip.com/downloads/en/AppNotes/00905a.pdf

These show a full bridge controller, which is more complex than a single
MOSFET with PWM, but it is really much better because it can reverse
direction under software control, and you can also use dynamic braking
which slows the motor more quickly and provides more precise control.

If you really want good control, a stepper motor is best. The PIC16F684 is
also usable for stepper motors, and I have had some experience with that
device if you want to go that route.
http://ww1.microchip.com/downloads/en/AppNotes/00906B.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00907a.pdf

But stepper motors are even more complex, and I think you want something
very simple. Still, the PIC16F684 would be able to provide a nice PWM drive
to a logic level MOSFET at 5 kHz, and you could add a pot across the 5 VDC
power supply to an A/D pin, and you could have a complete PWM circuit with
only a few components. And you could change the frequency just by
reprogramming it, or add other things like pushbuttons, LEDs, and even
literally "bells and whistles".

You can use a PICkit 1 (which I have) to build your entire motor
controller. It connects by a USB cable to your computer for programming,
and it has a prototyping card that can be snapped off and used separately.
There is also a PICkit 2 that has more features. Here's more info:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en010053

And for the PICkit 2:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023805

I could give you a PC board that could be used to make a simple PWM motor
control using a PIC16F684 or the similar PIC16HV616 (which I am using). The
board is designed to produce up to 60 VDC at 750 mA as a boost converter,
but you could replace the inductors with a motor (and diode), and you could
add an external pot for speed control. But it's only about 1" x 2.5", and
mostly SMT. I got about 100 boards for about $150, and I could spare a few.

I also have about 100 boards that were designed for an LT1247 or UC1843a
PWM controller, and they might work also. It's a simple IC, and you could
get a free sample in DIP package from Linear Technology or TI. The boards
are essentially scrap, and I have some extra parts, so let me know if you
(or anyone else) is interested. Again, this was for a boost converter, and
it works, but not quite right.

Sorry for getting carried away, but these are just some other ideas that
might help you with your project, and maybe you might enjoy a more
software-oriented approach to circuit design with PICs.

Good luck,

Paul

 

[Electronworks.co.uk Elect]

What about a 556 timer (dual 555).
Wire one in monostable mode (to give a single shot output that is
controllable) - this is your duty cycle.

Trigger it with the other 555 running in astable mode - this is your
frequency

Let me know your thoughts
Bill Naylor
Electronworks.co.uk - electronic kits for education and fun

"lerameur" <lerameur@yahoo.com> wrote in message
news:85477911-c01f-4d14-83e7-8924477e41bc@k30g2000hse.googlegroups.com...

Hi,

anybody know of an oscillator or multivibrator than I can crontrol
both frequency and duty cycle. I tried to find a chip like the CD4047
but with variable duty cycle. My output needs to be about 12v.
I also looked at the 555 timer, but it is hell to tune the duty cycle
as the frequency changes.
Maybe there is a circuit out there with a 555 that has fixed frequency
and variable duty cycle?


thanks

Ken

 

[Electronworks.co.uk Elect]

Firstly, I have seen your correction about the Vcc = 12V. Do you have the
ground pin connected properly? Dry joints on this pin can cause you hours of
undeserved fun.

Check this, then tie a load to the output (1k should be OK) and check the
output.

Have you got the output connected to anything that could be keeping the
output high?

Also, not related to this problem, make sure your decoupling caps are close
to the Vcc pin to get best transient response from FET drivers once the
circuit is working

Let me know

Rgds Bill Naylor
Electronworks.co.uk - electronic kits for education and fun


"lerameur" <lerameur@yahoo.com> wrote in message
news:c9418969-3c09-4635-8b38-3ed1f5f6f210@k30g2000hse.googlegroups.com...

Hi,

I am trying to use the TC4432. I am doing the exact circuit of page 7
below. My Vdd is at 1v, and my input is coming from a pic chip running
at 10khz 60% duty cycle.

http://www.datasheetcatalog.com/datasheets_pdf/T/C/4/4/TC4432.shtml
page 7 of microchip

What I am getting at the output is oscillation between 10v low to 12v
high. The frequency is good, but it is not coming down to zero volt
like expected. Any body used this chip and can show me a working
circuit or have any ideas why that is?

thanks

K

 

[Bob Masta]

On Thu, 18 Sep 2008 08:13:49 -0700 (PDT), lerameur
<lerameur@yahoo.com> wrote:

Hi,

anybody know of an oscillator or multivibrator than I can crontrol
both frequency and duty cycle. I tried to find a chip like the CD4047
but with variable duty cycle. My output needs to be about 12v.
I also looked at the 555 timer, but it is hell to tune the duty cycle
as the frequency changes.
Maybe there is a circuit out there with a 555 that has fixed frequency
and variable duty cycle?

See Don Lancaster's "CMOS Cookbook", pages
228-231. The basic idea is to use a simple 2-gate
(inverter) oscillator. Inverter 1 provides the
output, which goes through C to a node that feeds
the input of inverter 2 through 470K, and also
connects the feedback (frequency setting) resistor
R from the node to the output of inverter 2. The
output of inverter 2 connects directly to the
input of inverter 1.

That's the basic oscillator, where R and C set the
frequency. To vary the duty cycle as well, you
use a pot for R, with the wiper connected to the
output of inverter 2. The legs of the pot connect
back to the C node through diodes with reversed
polarities.

One problem with this is that R sets the
frequency, and the duty cycle is set by the
proportion of R to each diode. Just changing the
single pot setting only changes the duty cycle,
but not the main frequency. To vary both, you
need a second pot in series with the R pot, but
then you reduce the range of duty cycles.

On the other hand, if you don't need intuitive
separate frequency and duty cycle controls, just
replace the R pot with two separate pots as
adjustable resistors. Each one will affect both
frequency and duty cycle, but together you will
get a huge range of both.

Best regards,




Bob Masta

DAQARTA v4.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!

 

[Bob Masta]

On 19 Sep 2008 02:32:49 GMT, Jasen Betts
<jasen@xnet.co.nz> wrote:

On 2008-09-18, Patrick Keenan <test@dev.null> wrote:
Hello All,
I've recently posted on another topic, and thanks for the varied replies,
which gave me the information I needed.

I've another question regarding digital control of resistance. I have an
application where I'd like to add digitally controlled resistance to
pre-existing devices, where I can't modify anything except the resistance
control itself. I can't alter the circuit in any other way. For an
example, think of a "vintage" wah-wah pedal - in this case, pots do wear out
so it's acceptable to replace that part - but that part only. One can't
redo the circuit to match the pot, as that could alter the tone...

I'm aware that there are digital potentiometers, but I have been finding
that in a number of cases these just are not available in the values I might
need to match the existing potentiometer, and/or may not be able to handle
the current or voltage that might be present (such as in a guitar
amplifier).

So my question would be, what other kinds of resistive devices could be used
to provide a digitally controllable resistance?

a motorised dual gang pot in a servo circuit ?

an ORP7 (or similar LDR) illuminated by a LED. (pwm at some ultrasonic rate)

an ordinary pot driven by an off-the shelf R.C. servo.

conbine two digital pots to give the range you want.

All good ideas. One unusual addition is to use a
CMOS switch to apply PWM to a fixed resistor,
again at some ultrasonic rate. At low duty cycles
there is less current through the resistor, so its
value appears to be larger. This works especially
well for circuits like wah pedals that are
essentially low-pass anyway.

For new designs, there is the advantage that you
can have as many variable Rs as you want... and
_they_all_track_perfectly with a single PWM
signal. Works great for phaser/flanger circuits,
where each stage adds another sliding notch to the
output spectrum.

Credit for this idea goes to Don Lancaster's "CMOS
Cookbook"... strongly recommended!


Bob Masta

DAQARTA v4.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!

 

[Kevin Aylward]

jalbers@bsu.edu wrote:

I have been trying to follow along with a books calculation for the
input resistance of a transistor which they define as Rin = delta
(Vbe) / delta (Ib) or Rin would be 1 / (slope of the diode curve) or
1 / (derivitive of the diode curve) . Doing the math and assuming
that KT/Q = 26 mv and assuming that (Is) the reverse saturation
current is negligible, I get the desired Rin = 26 mv / Ib.

It may be better to think of this as:

rin = hie = rbb' + (1 + hfe).re

where rbb' is the base resistace, usually of the order 10-500 ohms, and
re=1/(40.IC) = 1/gm

My question is why is Rin = delta (Vbe) / delta (Ib) and not just
Vbe / Ib . My some how flawed reasoning is that if you look at ohms
law E = IR, then R = I/E and therfore Rin should be Vbe / Ib . Why
is Rin equat to the change in current divided by the change in
voltage?

Any help would be greatly appreciated. Thanks

The fundamental reason is:

del_y = f'(x).del_x

if del_y, and del_x are small, as a general math result, from differential
calculus.

For small signals, i.e., when an input signal only changes a small amout
about a fixed bias point, what is the resulting change in the output, about
a fixed bias.

rin, is a small signal resistance. It is not equal to VINDC/INDC. Since the
inputs and outputs that are wanted are the small signal changes, than one
needs the small signal resistance, not the large signal resistance. If one
actually wanted large signal values, than one would use such values
throughout.

Kevin Aylward
kevin@kevinaylward.co.uk
www.kevinaylward.co.uk

 

[Kevin Aylward]

John Popelish wrote:

jalbers@bsu.edu wrote:

My question is why is Rin = delta (Vbe) / delta (Ib) and not just
Vbe / Ib . My some how flawed reasoning is that if you look at ohms
law E = IR, then R = I/E and therfore Rin should be Vbe / Ib . Why
is Rin equat to the change in current divided by the change in
voltage?

Because the resistance is not ohmic.

Interesting point. The resistance does not follow ohm's law, so in that
sense is not ohmic. However, it does have characteristic similar to ohmic
resistors but not similar inductors and capacitors. That is, the current and
voltage are independent of time, i.e not +/-j

For DC conditions, the actual value of V/I may be important, especially for
values of Vdc of around 0.5 to 1V.

Ohmic resistances hold
a constant ratio of voltage to current, regardless of the
magnitude of voltage or current. Diode junctions do not.
So resistance can be defined for such devices only
incrementally (over tiny ranges of voltage and current).

Well... technically one can actually define the large signal resistance as
V/I.

So that:

R = Vd/I = (Vd/Io).exp(-Vd/Vt)

And using the results of
http://www.kevinaylward.co.uk/ee/widlarlambert/widlarlambert.html, for the
Lambert W() function

One can obtain the inverse relation;

Vd = -Vt.W(-R.Io/Vt)

I will leave it as an exercise for the reader to deduce formulas expressing
R in terms of I, and I in terms of R

Kevin Aylward
www.blonddee.co.uk
www.anasoft.co.uk

 

[amdx]

"Arnold" <aspoor@freemail.nl> wrote in message
news:4a9d87c6-69a5-4151-ade7-b7de73666991@k13g2000hse.googlegroups.com...

1) I am wondering whether the piezo ignitor of a BBQ lighter generates
a single spark or multiple sparks.

2) In other words, I would like to know the pulse shape of the piezo
ignitor, but I haven't got an oscilloscope. Is it AC or DC, is it a
single monopolar pulse, or a bipolar pulse, or a dampened
oscillation?

Probably the pulse shape depends on its design, so I dissected a piezo
ignitor. Please see the image at
http://s365.photobucket.com/albums/oo98/jkien_photos/?action=view&current=IMG_6175.jpg
The piezo electric body is apparently composed of some indistinct grey
matter in a relatively large brass cup.
3) is the grey matter the piezo ceramic (PZT)?
4) what is the purpose of the relativey large brass mass. Is it just a
heavy anvil?

Take a look at this page, do a find for PZT on the page. It shows
waveforms and Q. Although I
don't make any sense of either of those. I think the voltage and the Q is
much higher
than what it says.
physics.mercer.edu/hpage/technique.htm

Mike

 

[Jon Slaughter]

"FyberOptic" <fyberoptic@gmail.com> wrote in message
news:37b11c97-0f44-4fd2-afad-a3f81a007783@r66g2000hsg.googlegroups.com...

I'm having a bit of a quandary. Since I'm still somewhat of a
beginner, I hope somebody more experienced can help me out!

I have three TTL logic chips, with one input on each one all connected
together to a single input signal. When that main signal wire is
connected to ground, the logic chip signals are all low as expected.
When I remove the ground connection though, they seem to all go high
on their own without being connected anywhere (aside from to each
other). This isn't my problem exactly, but I'm curious if someone can
explain it.

It's called floating. The state is usually undefined but because of unknown
factors it could set it to either state. That or internally there is a
pullup.

(are you sure it's continuously high and not toggling back and forth very
rappidly?)

So I need a pull-down on that main input signal to keep the inputs
it's connected to forced low unless a high is explicitly introduced.
The main input signal itself will be connected to a pin coming out of
a chip elsewhere, which is switchable between being an input and
output. At startup, that pin is an input, so it's not outputting a
low like I want, hence the need for a pull-down.

Where the actual problem comes in is that when I add a "normal" pull-
down resistor value between the input signal and the ground, it
behaves as if it's not connected to ground at all. I've tried a few
different ones, from 100k, to 50k (didn't have a 47k), down to 4.7k.
I couldn't figure it out. Then finally I tried a 1k, and it seems to
properly pull it down low. Keep in mind that this isn't even
currently connected to the other chip I mentioned which will default
to an input at startup, this is just the input signal being connected
to ground or left floating. Is having to use such a low pull-down
resistor because I have three inputs connected together? Is there a
resistance inside the IC I'm not taking into account when connecting
it up like this? My assumption is that a "normal" 10k-47k pulldown
value assumes only a single input is being connected to. A possible
worry I have though is that the 1k resistor is kind of low and could
be wasting power (since it will be able to run from batteries), but I
dunno.

My bet is that there is an internal pullup. By adding your pulldown it works
in parallel resulting in a voltage divider.

I'd appreciate any light anyone can shed on how these things work!

What is the logic family? (e.g. what is the numbers on the chips)

Some chip families work better than others.

As Jasen mentioned, I'd end up using some form of low power cmos rather than
bipolar. You need to choose the right family if you are worried about power
loss. Some families are high speed which you might not need.

In any case the cmos families(or equivalents) are usually a direct
replacement so there is not that big a deal. (there are a few issues with
have to do with thresholds but I doubt you'll have those problems)

If I were you I'd probably look at a few alternatives to bipolar.

http://en.wikipedia.org/wiki/7400_series

somewhere there is also a chart that shows the power consumption
differences.