Chip with simple program for Toy

[Chris]

Racer wrote:
<snip>

Perhaps you shoul;d consider writing a book for dummies
like myself ! ........

Thanks so much Chris .......

/Racer

You're welcome. Business is slow in these parts, so I'll sometimes
have a chance to answer in a little depth.

I like the "dummies" books, and sometimes recommend them to customers
who aren't familiar with Excel or something, but newbies aren't
"dummies". We were all there once.

If you want a good introduction to electronics, just Google
sci.electronics.basics or sci.electronics.design for a number of
threads on books and magazines for newbies. In particular, I would
recommend the books and magazine articles by the author of one of the
responses, Don Lancaster. In addition to writing the CMOS, TTL and RTL
cookbooks, he's been a feature writer for several electronics magazines
over the years. I remember buying the CMOS cookbook when it first came
out. Answering your post, I was thinking how cool it would have been
back in the days when "Kansas City Standard" 300 baud modems ruled the
earth to actually have Mr. Lancaster pop up to answer a newsgroup post
on the "internets" back then. The amazing thing is that 95% of what's
in the CMOS Cookbook is still relevant, and you can still learn a lot
about electronics from it.

Most everything Mr. Lancaster has written is available from his
website, either free or for purchase. I still keep a copy of his
Active Filter Cookbook in a desk drawer.

Browse around -- this is one of the best electronics newbie sites out
there.

http://www.tinaja.com/

Good luck
Chris

 

[John Fields]

On 22 Feb 2005 21:39:56 -0800, "Chris" <cfoley1064@yahoo.com> wrote:

Hi, Racer. Let's recap the bidding. You want to switch a digital
output (logic 1, 0) at around 0.658V analog input voltage. It's been
recommended that you use a voltage reference and a pot to get your
voltage reference, and that you use a comparator with hysteresis to
avoid "chatter" or multiple logic transistions as your signal passes
through the reference voltage. You now want to have something
inexpensive which will light one of two LEDs depending on the input
voltage. How does "free" sound?

The LM393 is a dual comparator, and you can use the other comparator to
drive the other LED. This might be what you need (view in fixed font
or M$ Notepad):

VCC VCC VCC
+ + +
| | |
4.7K| Red | Green|
.-. V ~ V ~
| | V(in) ___ - ~ - ~
| | o-|___|-o---. 1/2 LM393 | |
'-' 10K | | | |
| --- | VCC .-. .-.
| .01uF--- | + | |1K 1K| |
o---------. | | | | | | |
| | === | |\| '-' '-'
| 10K| GND '-----|-\ | |
LM385| .-. ___ | >---o |
/-/ NC | |<-|___|-o----|+/ | |
^ ---o | | 10K | |/| | |
| '-' | === | |
| | | GND | |
=== | | ___ | 1/2 LM393|
GND === o----|___|--o |
GND | 1M | |\ |
| '----|-\ |
| | >--'
'----------------|+/
|/
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Your input voltage is low-pass filtered by the 10K resistor and .01uF
cap to help with noise on the input causing false transitions. The
LM385 (a voltage reference which provides about 1.23VDC) is put through
the 10K pot to give you the precise 0.658VDC. The 10K and 1M resistors
are set up to give you the required hysteresis (values assume a 12VDC
supply). The open collector current sinking output of the first
comparator drives the Red LED (with the 1K resistor, set to give you
10mA LED current with a 12VDC supply). Since the output will be either
close to 12VDC or a couple hundred millivolts, the reference and the
output of the first comparator are used to drive the second comparator,
which drives the green LED.

One and only one LED will always be on. If the logic sense of the two
LEDs is wrong, just switch 'em around.

---
A few thoughts:

Assuming a common pot with a rotation of 270° and 1.23V across it, its
sensitivity would be about 4.56mV/°, so it might be difficult to set
it precisely to 0.685V, that LSD corresponding to roughly 1°.

Also, with 1 megohm of feedback the hysteresis will be about 150mV,
not 15mV.

An LM393 has a saturation voltage of 700mV max with only 4mA of
collector current, so with 10 mA of collector current in the red
comparator, it's conceivable that the saturation voltage could be
higher than the reference, making it impossible for the green LED to
ever turn off.

Also, I'm not a big fan of putting hysteresis on the reference, so
here's how I'd do it:

newsrcp115sbgjnp0385l8n9d35i8t1d9vn05@4ax.com

--
John Fields

 

[John Fields]

On Thu, 24 Feb 2005 05:02:27 +0800, Racer <racer007@tm.net.my.> wrote:

On Wed, 23 Feb 2005 10:49:30 -0600, John Fields
jfields@austininstruments.com> wrote:


Also, I'm not a big fan of putting hysteresis on the reference, so
here's how I'd do it:

newsrcp115sbgjnp0385l8n9d35i8t1d9vn05@4ax.com

Mind (re)posting the article here or e-mailing it to me?
thnx!

---

+V----+------+----------------+----+---+----+
| | | | | |
[R] | [R] | | [R]
| [R] +--[R]---+ | [R] | |
| | | | [LED] | | [LED]
[POT]<-------+--|+\ | |K | | |K
| | | >--+---+-------|-\ |
| +------|-/ | | >--+
[R] | +--|+/
| |K | |
| [REF] [R] |
| | | |
GND>--+------+---------------------+---+

--
John Fields

 

[Jim Thompson]

On Thu, 24 Feb 2005 16:39:19 +0100, Spajky <Spajky@##volja.net> wrote:

[snip]

Italians with groups like this on their local ones
like it.hobby.elettronica
use interesting program to draw & see schematics for posting
in text only usenet IMHO much bettter than ASCII ...

its FidoCAD (maybe someone could write to the author to make an
English interface & help file for it). Can be found here: less than
1Mb installed:
http://www.enetsystems.com/~lorenzo/fidocad_win.asp

you draw a standard schematic, export it as text & paste it into a
message like this (pasted code) interesting oscillator:

[FIDOCAD]
MC 85 45 0 0 580
MC 70 45 1 0 170
[snip]
TY 115 25 5 3 0 0 0 * 100n
TY 155 45 5 3 0 0 0 * 34kHz
TY 75 35 5 3 0 0 0 * LM6181

You to see it with that installed program, just copy that upper
complete code, open the program, from menu open:
modifica/incolla/come nuovo documento .... & so you see the
schematics like usuall one; IMHO not a bad trick ... & easier than
ASCII pics schematics ...

Try it 4 fun ...

Why not then just use a readily available, and free, program such as
Mike Engelhardt's LTSpice? (Or an old copy of MicroSim Schematics for
that matter?)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Racer]

On 23 Feb 2005 12:47:16 -0800, "Chris" <cfoley1064@yahoo.com> wrote:

John Fields wrote:

Thanks John .....

` VCC VCC
` VCC + +
` + | |
` | .-. .-.
` 4.7K| | | | |
` .-. | | | |
` | | V(in) ___ VCC '-' '-'
` | | o-|___|-o---. + | |
` '-' 10K | | | Red| Green|
` | --- | VCC .-. V ~ V~
` | .01uF--- | + | |10K - ~ -~
` o---------. | | | | | | |
` | | === | |\| '-' | |
` | 1K| GND '-----|-\ | ___ |/ VCC |
` LM385| .-. ___ | >--o-|___|-|2N3904 + |
` /-/ NC | |<-|___|-o----|+/ | 10K |> | |
` ^ ---o | | 2.2K | |/| | | .-. |
` | '-' | === | === 10K| | |
` | | | GND | GND | | 2N3904|
` === | | ___ | |\ '-' |
` GND === o----|___|-o-------------|-\ | ___ |/
` GND | 2.2M | >-o-|___|-|
` | .-------------|+/ 10K |
` | | |/ |
` '----------' ===
` GND
`created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

This is just for reference. Thanks for the spot, Mr. Fields.

Chris

At the risk of becoming a nuisance to you Electronic Pros,
I pose yet another so called "simple" question.....
From what point in the circuit and how would you provide
the operating power to drive a basic fixed frequency
( approx. 600 Hz ) oscillator that drives a (very) small
0.2 watt speaker (and includes a user volume control)
such that this oscillator comes ON in tandem with the
Green LED above?
It wouldn't matter if the negative rail of this oscillator was
and output stage was above the "GND" potential.
Again, low component count and cost. would be an
important consideration.

TIA

 

[Chris]

Racer wrote:

At the risk of becoming a nuisance to you Electronic Pros,
I pose yet another so called "simple" question.....
From what point in the circuit and how would you provide
the operating power to drive a basic fixed frequency
( approx. 600 Hz ) oscillator that drives a (very) small
0.2 watt speaker (and includes a user volume control)
such that this oscillator comes ON in tandem with the
Green LED above?
It wouldn't matter if the negative rail of this oscillator was
and output stage was above the "GND" potential.
Again, low component count and cost. would be an
important consideration.

TIA

It sounds like the LM555 might do the job for you. It can be hooked up
with a couple of resistors and a cap to oscillate at around 600Hz, and
it can easily drive an 0.2 watt speaker.

The control would be through the reset pin (pin 4). When it's low, it
don't go. So you can connect the 555 pin 4 to the collector of the
transistor that's driving your _RED_ LED, and then do something like
this (view in fixed font or M$ Notepad):

` From Transistor Collector
` >---------------------.
` |
` VCC VCC |
` + + |
` | | |
` .-. | |
` | | | |
` 4.7K| | | |
` '-' .---o----o-----.
` | | 8 4 |
` | | Reset |
` o-----o7 |
` | | | 22uF
` .-. | | +|| ___
` | | | 3o---||--|___|--.
` 10K| | | LM555 | || 270 ohm|
` '-' | | |
` | .--o6 | .-. __ /|
` | | | | 1K| |<---| | |
` | | | | | | .--|__| |
` o--o--o2 | '-' | \|
` | | | | |
` 0.1uF| | 1 5 | | |
` --- '---o-----o----' | |
` --- | | | |
` | | NC | |
` === === =====` GND GND GNDGND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

The above again assumes you have a 12VDC supply. If you have a 5VDC
supply, change the 270 ohm resistor to a 100 ohm.

You might want to take a chance to educate yourself about the 555. One
good place to start is the datasheet:

http://www.national.com/pf/LM/LM555.html#Datasheet

Here's a good site which provides some basics, including a description
of the 555 internal action:

http://www.uoguelph.ca/~antoon/gadgets/555/555.html

And of course, there's also Chapter 4 of the TTL cookbook by Mr.
Lancaster:

http://www.tinaja.com/books/bkdons.asp

Good luck
Chris

 

[Racer]

On 25 Feb 2005 03:46:47 -0800, "Chris" <cfoley1064@yahoo.com> wrote:

Racer wrote:

At the risk of becoming a nuisance to you Electronic Pros,
I pose yet another so called "simple" question.....
From what point in the circuit and how would you provide
the operating power to drive a basic fixed frequency
( approx. 600 Hz ) oscillator that drives a (very) small
0.2 watt speaker (and includes a user volume control)
such that this oscillator comes ON in tandem with the
Green LED above?
It wouldn't matter if the negative rail of this oscillator was
and output stage was above the "GND" potential.
Again, low component count and cost. would be an
important consideration.

TIA

It sounds like the LM555 might do the job for you. It can be hooked up
with a couple of resistors and a cap to oscillate at around 600Hz, and
it can easily drive an 0.2 watt speaker.

The control would be through the reset pin (pin 4). When it's low, it
don't go. So you can connect the 555 pin 4 to the collector of the
transistor that's driving your _RED_ LED, and then do something like
this (view in fixed font or M$ Notepad):

` From Transistor Collector
` >---------------------.
` |
` VCC VCC |
` + + |
` | | |
` .-. | |
` | | | |
` 4.7K| | | |
` '-' .---o----o-----.
` | | 8 4 |
` | | Reset |
` o-----o7 |
` | | | 22uF
` .-. | | +|| ___
` | | | 3o---||--|___|--.
` 10K| | | LM555 | || 270 ohm|
` '-' | | |
` | .--o6 | .-. __ /|
` | | | | 1K| |<---| | |
` | | | | | | .--|__| |
` o--o--o2 | '-' | \|
` | | | | |
` 0.1uF| | 1 5 | | |
` --- '---o-----o----' | |
` --- | | | |
` | | NC | |
` === === ======
` GND GND GNDGND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

The above again assumes you have a 12VDC supply. If you have a 5VDC
supply, change the 270 ohm resistor to a 100 ohm.

You might want to take a chance to educate yourself about the 555. One
good place to start is the datasheet:

http://www.national.com/pf/LM/LM555.html#Datasheet

Here's a good site which provides some basics, including a description
of the 555 internal action:

http://www.uoguelph.ca/~antoon/gadgets/555/555.html

And of course, there's also Chapter 4 of the TTL cookbook by Mr.
Lancaster:

http://www.tinaja.com/books/bkdons.asp

Good luck
Chris

Thank you Chris ......

/Racer

 

Michael A. Terrell wrote:

bill.sloman@ieee.org wrote:

Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:

I don't know what Don Lancaster does.

---------
Bill Sloman, Nijmegen

That figures. He's well known in the US.

This is a prime example of text-chopping - what I was saying was
that I
don't know if Don Lancaster answers private e-mails.

I replied the way it looked. Be specific. If you meant: I don't
know
if Don Lancaster answers private e-mails." then write it, don't just
think it.

Here is the text in context.

"> Would an e-mail to consult with you personally be replied?

Chris Carlen has suggested a simple way of dealing with the LEDs.

I usually respond to direct e-mails - my e-mail address is real. I
don't know what Don Lancaster does. "

My wife (who is an expert on language - which is what she was doing at
MIT) tells me that I should have written "I don't know whether Don
Lancaster does" if I'd wanted to avoid wilful misundertandings, but
this imposes a binary choice on a what is really a rather wide range of
possibilities.

-------
Bill Sloman, Nijmegen

 

[Duane C. Johnson]

Antipodean Bucket Farmer wrote:

I seem to recall hearing of 12 volt LEDs designed as
drop-in replacements for automotive/truck lamps in
tail-lights, etc.

12V visible light LEDs can't exist.
They would be in the hard ultra violet.

What you are describing are circuits of multiple
LEDs and ballast resistors and such.

Duane

--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/electron.htm#led3X [*]
Powered by \ \ \ //|
Thermonuclear Solar Energy from the Sun / |
Energy (the SUN) \ \ \ / / |
Red Rock Energy \ \ / / |
Duane C. Johnson Designer \ \ / \ / |
1825 Florence St Heliostat,Control,& Mounts |
White Bear Lake, Minnesota === \ / \ |
USA 55110-3364 === \ |
(651)426-4766 use Courier New Font \ |
redrok@redrok.com (my email: address) \ |
http://www.redrok.com (Web site) ===

 

[Michael A. Terrell]

bill.sloman@ieee.org wrote:

My wife (who is an expert on language - which is what she was doing at
MIT) tells me that I should have written "I don't know whether Don
Lancaster does" if I'd wanted to avoid wilful misundertandings, but
this imposes a binary choice on a what is really a rather wide range of
possibilities.

-------
Bill Sloman, Nijmegen

My point is, this is a worldwide forum where people have different
backgrounds, languages and abilities. I try to make things clear when I
post or write a technical article. Its very easy to be to close to what
you write. It makes perfect sense to you but not to someone casually
reading it. No need to get all bent out of shape. I am starting to
loose my eyesight and it is getting easier to misread something, or take
it the wrong way because of the wording.

I notice you snipped the part about BYTE. I had three copies of
issue number one, and two were still in the mailing wrappers. I gave
the extras away and filled in a few missing holes in my collection. I
liked the magazine when it first came out. A lot of surplus hardware
hacking and some basic digital designs to study. I have see post from
some of the authors on the newsgroups over the years. Later on it was
mostly ads for different brands of computers disguised as reviews.


--
Beware of those who post from srvinet.com!

Michael A. Terrell
Central Florida

 

[Rich Grise]

On Fri, 25 Feb 2005 15:20:32 +0800, Racer wrote:

On 23 Feb 2005 12:47:16 -0800, "Chris" <cfoley1064@yahoo.com> wrote:
John Fields wrote:


` VCC VCC
` VCC + +
` + | |-*
` | .-. .-.
` 4.7K| | | | |
` .-. | | | |
` | | V(in) ___ VCC '-' '-'
` | | o-|___|-o---. + | |
` '-' 10K | | | Red| Green|
` | --- | VCC .-. V ~ V~
` | .01uF--- | + | |10K - ~ -~
` o---------. | | | | | | |
` | | === | |\| '-' | |
` | 1K| GND '-----|-\ | ___ |/ VCC |
` LM385| .-. ___ | >--o-|___|-|2N3904 + |
` /-/ NC | |<-|___|-o----|+/ | 10K |> | |
` ^ ---o | | 2.2K | |/| | | .-. |
` | '-' | === | === 10K| | |
` | | | GND | GND | | 2N3904|
` === | | ___ | |\ '-' |-*
` GND === o----|___|-o-------------|-\ | ___ |/
` GND | 2.2M | >-o-|___|-|
` | .-------------|+/ 10K |
` | | |/ |
` '----------' ===
` GND
At the risk of becoming a nuisance to you Electronic Pros,
I pose yet another so called "simple" question.....
From what point in the circuit and how would you provide
the operating power to drive a basic fixed frequency
( approx. 600 Hz ) oscillator that drives a (very) small
0.2 watt speaker (and includes a user volume control)
such that this oscillator comes ON in tandem with the
Green LED above?
It wouldn't matter if the negative rail of this oscillator was
and output stage was above the "GND" potential.
Again, low component count and cost. would be an
important consideration.

Take an ordinary piezo buzzer or beeper, and put it between the
right-hand 2N3904's collector and Vcc, where I've marked with -*.
Here's nust one page of beepers:
http://www.peats.ie/cgi-bin/shop/db.cgi?view=1&id=304&type=5&path=13x119
or try one of these:
http://www.google.com/search?q=piezo+beeper&btnG=Search

Good Luck!
Rich

 

[Robert Monsen]

Racer wrote:

On 23 Feb 2005 12:47:16 -0800, "Chris" <cfoley1064@yahoo.com> wrote:


John Fields wrote:

Thanks John .....


` VCC VCC
` VCC + +
` + | |
` | .-. .-.
` 4.7K| | | | |
` .-. | | | |
` | | V(in) ___ VCC '-' '-'
` | | o-|___|-o---. + | |
` '-' 10K | | | Red| Green|
` | --- | VCC .-. V ~ V~
` | .01uF--- | + | |10K - ~ -~
` o---------. | | | | | | |
` | | === | |\| '-' | |
` | 1K| GND '-----|-\ | ___ |/ VCC |
` LM385| .-. ___ | >--o-|___|-|2N3904 + |
` /-/ NC | |<-|___|-o----|+/ | 10K |> | |
` ^ ---o | | 2.2K | |/| | | .-. |
` | '-' | === | === 10K| | |
` | | | GND | GND | | 2N3904|
` === | | ___ | |\ '-' |
` GND === o----|___|-o-------------|-\ | ___ |/
` GND | 2.2M | >-o-|___|-|
` | .-------------|+/ 10K |
` | | |/ |
` '----------' ===
` GND
`created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

This is just for reference. Thanks for the spot, Mr. Fields.

Chris



At the risk of becoming a nuisance to you Electronic Pros,
I pose yet another so called "simple" question.....
From what point in the circuit and how would you provide
the operating power to drive a basic fixed frequency
( approx. 600 Hz ) oscillator that drives a (very) small
0.2 watt speaker (and includes a user volume control)
such that this oscillator comes ON in tandem with the
Green LED above?
It wouldn't matter if the negative rail of this oscillator was
and output stage was above the "GND" potential.
Again, low component count and cost. would be an
important consideration.

TIA

What fun. If you aren't too picky about the voltage it turns on, you can
use a silly circuit like this:

http://home.comcast.net/~rcmonsen/light-buzz.GIF

It turns on when the input is near Vbe of Q2, which is generally between
0.65 and 0.7V.

The schmitt trigger gives you a (tiny) bit of hysteresis. The oscillator
is inhibited until the input circuit turns on. The power stage gives you
a reasonably loud 600Hz whine. Use a 100 ohm rheostat in series with the
speaker to limit the output. A bigger cap than 10uF will allow more of
the power to come through. If you us an electrolytic, put the - side
towards the speaker.

The LEDs are turned on and off by complimentary transistors, tied to the
output of the schmitt trigger.

You can make it more accurate w.r.t. input by using a differential amp
on the input, along with a reference. However, you may not care.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[John Fields]

On Fri, 25 Feb 2005 15:20:32 +0800, Racer <racer007@tm.net.my> wrote:

At the risk of becoming a nuisance to you Electronic Pros,
I pose yet another so called "simple" question.....
From what point in the circuit and how would you provide
the operating power to drive a basic fixed frequency
( approx. 600 Hz ) oscillator that drives a (very) small
0.2 watt speaker (and includes a user volume control)
such that this oscillator comes ON in tandem with the
Green LED above?
It wouldn't matter if the negative rail of this oscillator was
and output stage was above the "GND" potential.
Again, low component count and cost. would be an
important consideration.

---
Here's something that ought to do everything you asked for, plus
taking care of the variation in the supply voltage. The only problem
might be that the hysteresis is asymmetrical. About 15mV when the
input goes higher than 0.658V and about 5mV when it goes lower than
0.658V. The speed-up capacitor, C2, will help, though.

news:m58121hqp6lq6e4qgv95u0rpe07r3kmd2d@4ax.com

--
John Fields

 

[John Fields]

On Sat, 26 Feb 2005 17:21:43 GMT, Fred Bloggs <nospam@nospam.com>
wrote:

John Fields wrote:
On Fri, 25 Feb 2005 15:20:32 +0800, Racer <racer007@tm.net.my> wrote:

---
Here's something that ought to do everything you asked for, plus
taking care of the variation in the supply voltage. The only problem
might be that the hysteresis is asymmetrical. About 15mV when the
input goes higher than 0.658V and about 5mV when it goes lower than
0.658V. The speed-up capacitor, C2, will help, though.

news:m58121hqp6lq6e4qgv95u0rpe07r3kmd2d@4ax.com


You need to use R10 to pull-up to 3.3V and run the OC output direct to
the base.

---
Yes, thank you.

--
John Fields

 

[Robert Monsen]

Racer wrote:

Thank you Robert ! .....
Is the above link your web site?

Personal pages, courtesy comcast.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[Don Bruder]

In article <1gsmf90.d58liu7di2a0N%LEDMan@3v.invalid>,
LEDMan@3v.invalid (LED Man) wrote:

I have a solar powered torch, battery 2.4v 280mah nicad, hard pcb wired.

I am thinking of wiring up a second nicad battery 750 mah in parallel.

My question, when one nicad, probably the 280 mah dies, what happens ?

Does it go open circuit, closed circuit,

Depends on failure mode - Did it die of pure old age? It probably went
short, then. Did it die of abuse (rough handling/vibration?) Likely it
went open, but it's impossible (without having it in hand, anyway) to
say it didn't short.

how does it affect charging and
useage of the higher capacity nicad

Gonna depend on how it fails. If open, probably very little, if any,
effect. If short, it'll probably drain the other one quickly, and/or
prevent charging at all.

Any experience of same ??

No actual experience this way, but common sense says it isn't likely to
be a good idea. I'd pick one or the other, and use that one exclusively.
No point in messing around, I'd say...

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.

 

[LED Man]

CWatters <colin.watters@pandoraBOX.be> wrote:

"LED Man" <LEDMan@3v.invalid> wrote in message
news:1gsmf90.d58liu7di2a0N%LEDMan@3v.invalid...
I have a solar powered torch, battery 2.4v 280mah nicad, hard pcb wired.

I am thinking of wiring up a second nicad battery 750 mah in parallel.

It's not generally a good idea to connect two voltage sources in parallel.
If the voltage of one is slightly different to the other (due to charge
state) what limits the current.....Hint I=(V1-V2)/R but R is very small if
it's wire.

My question, when one nicad, probably the 280 mah dies, what happens ?

What do you mean by "dies"? flat? old? faulty?

Most likely the larger battery will supply all the current when the smaller
on is empty but batteries can be unpredictable. Mostly it works if you
charge them both before connecting them but watch out for melted wires and
fire if one is empty!

how does it affect charging

With two voltage sources in parallel the results are unpredictable. Old
batteries tend to have a slightly higher voltage on charge so most of the
current may go into the larger external battery leaving the internal one
uncharged/less charged. If the larger battery is a different make it might
have a higher on charge voltage and all the current may go into the smaller
internal battery. Personally I would remove or disconnect the smaller
internal battery.

Caution: I've see batteries explode due to missuse. It's can be dangerous.

Ta

 

[PeteS]

As other have noted, depends on dies. If we are speaking simply of
discharging, then the (fairly) simple answer is that as the smaller
capacity battery gets more discharged, it's terminal impedance
increases, and the other battery supplies more of the current. Note
that NiCads in this state have rather horrendous leakage
characteristics, so the smaller battery may be taking charge from the
other battery too. In effect, the larger battery is charging the small
one, to a certain extent. Parallel batteries should always be of the
same type (type, construction and capacity).

Other things to watch out for are the exact type of battery. There are
different types of NiCad (optimised for a particular issue) and it is
very unwise to mix them. High temperature types, for example, can't
supply very much discharge current (<C/10 for some of them). The list
is rather lengthy.

Charging is a real issue - for ordinary (see note about different
types) NiCads, standard charge is C/10 for 14 hours (where C is the
capacity) so the 280mAh battery would need 28mA, but the larger one
75mA. If they were in parallel, it's very difficult to know the
effective terminal impedance of each (meaning you can't really properly
regulate the charge).
Some NiCads can never be fast charged (normally C/3 for 4.5hours)
although some can be boost charged (C rate for about 2 hours), but
again, you can't mix capacities in a charger without the distinct
possibility of killing the battery(ies), with a possibility of making
them come apart at the seams quite spectacularly.

Cheers

PeteS

 

[LED Man]

PeteS <ps@fleetwoodmobile.com> wrote:

As other have noted, depends on dies. If we are speaking simply of
discharging, then the (fairly) simple answer is that as the smaller
capacity battery gets more discharged, it's terminal impedance
increases, and the other battery supplies more of the current. Note
that NiCads in this state have rather horrendous leakage
characteristics, so the smaller battery may be taking charge from the
other battery too. In effect, the larger battery is charging the small
one, to a certain extent. Parallel batteries should always be of the
same type (type, construction and capacity).

Other things to watch out for are the exact type of battery. There are
different types of NiCad (optimised for a particular issue) and it is
very unwise to mix them. High temperature types, for example, can't
supply very much discharge current (<C/10 for some of them). The list
is rather lengthy.

Charging is a real issue - for ordinary (see note about different
types) NiCads, standard charge is C/10 for 14 hours (where C is the
capacity) so the 280mAh battery would need 28mA, but the larger one
75mA. If they were in parallel, it's very difficult to know the
effective terminal impedance of each (meaning you can't really properly
regulate the charge).
Some NiCads can never be fast charged (normally C/3 for 4.5hours)
although some can be boost charged (C rate for about 2 hours), but
again, you can't mix capacities in a charger without the distinct
possibility of killing the battery(ies), with a possibility of making
them come apart at the seams quite spectacularly.

Cheers

PeteS

Ta

 

[John Woodgate]

I read in sci.electronics.design that Larry Brasfield <donotspam_larry_b
rasfield@hotmail.com> wrote (in <z5pUd.27$d65.355@news.uswest.net&gt
about 'What's the transformer voltage at different currents ?', on Sun,
27 Feb 2005:

Multiply the RMS secondary voltage by sqrt(2).

The 24 V is almost certainly at full load, so under light load the r.m.s
voltage will be up to 10% high. So multiply by sqrt(2) and then by 1.05
to 1.1.

After all, 24 x sqrt(2) = 34 V, not 37 V. and that 37 V should be
increased to 38.4 V (not 39 V, I suggest) to allow for diode voltage
drops at low load In this case, the 24 V has risen by 13% on low load,
which is a bit unusual. Maybe the mains voltage was high when 37 V was
measured.

Subtract about 2 V for a
full bridge rectifier, or 1 V if you have a center-tapped secondary and
use only 2 diodes for rectification. Pretend that is the peak voltage
to which your filter cap will be charged. (It isn't, but it's close.)
Based on the load current, and assuming that it will flow for about 2/3
of each half line cycle, calculate the droop on the filter cap.

2/3 of a half cycle = 60 degrees conduction angle. You get this with
quite a lot of resistance in the transformer. I suggest a quarter cycle,
especially at low load.

Adjust
the pretend peak value downward by 4 times secondary resistance
multiplied by the DC load current. From those peak and droop values,
you can derive a decent estimate of the average filter cap voltage.

--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk