Chip with simple program for Toy

[Rich Grise]

On Sat, 19 Feb 2005 18:38:57 +0000, Fred Abse wrote:

On Thu, 17 Feb 2005 21:37:10 +0000, Rich The Newsgropup Wacko wrote:

On Wed, 16 Feb 2005 21:09:37 +0000, Fred Abse wrote:

[quoted text muted]

We used to electrolyze water, and demonstrate "rapid exothermic
recombination". ;-)

I was trying to dissolve some sulfur in some CS2 once, and used the logic
that if you heat up the solute, it helps speed solution. Until the CS2
reaches its flash point, of course. It's a weird feeling, being engulfed
in a ball of blue flame. =:-O


Remember the refractive index experiment, using a hollow prism, filled
with carbon disulfide and monochromatic sodium light from a piece of salt
in a Bunsen flame a few inches away?

Don't spill the CS2!

We didn't do that one, but I do remember a refractive index demo of some
liquid that has the same refractive index as glass. The prof. put a small
beaker inside a bigger beaker and poured this liquid into the big beaker,
and when the small beaker got covered up, it disappeared! I don't remember
if that was CS2 or not. )-;

Thanks,
Rich

 

[John Woodgate]

I read in sci.electronics.design that Fred Abse <excretatauris@cerebrumc
onfus.it> wrote (in <pan.2005.02.19.12.05.11.703230@cerebrumconfus.it&gt
about 'UV lamp question for ozone generation...', on Sat, 19 Feb 2005:

Remember the refractive index experiment, using a hollow prism, filled
with carbon disulfide and monochromatic sodium light from a piece of
salt in a Bunsen flame a few inches away?

No.

Don't spill the CS2!

No. (;-)

That's what our year 6 chemistry teacher did, over one of us! We tended
to avoid him....
--
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

 

[John Woodgate]

I read in sci.electronics.design that Rich Grise <richgrise@example.net>
wrote (in <pan.2005.02.19.18.45.24.751954@example.net&gt about 'UV lamp
question for ozone generation...', on Sat, 19 Feb 2005:

We didn't do that one, but I do remember a refractive index demo of some
liquid that has the same refractive index as glass. The prof. put a
small beaker inside a bigger beaker and poured this liquid into the big
beaker, and when the small beaker got covered up, it disappeared! I
don't remember if that was CS2 or not. )-;

No, in any case it's usually not sufficiently colourless. Spit! I can't
remember what the liquid actually is.
--
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

 

[Rich Grise]

On Sat, 19 Feb 2005 19:19:54 +0000, John Woodgate wrote:

I read in sci.electronics.design that Rich Grise <richgrise@example.net
wrote (in <pan.2005.02.19.18.45.24.751954@example.net&gt about 'UV lamp
question for ozone generation...', on Sat, 19 Feb 2005:

We didn't do that one, but I do remember a refractive index demo of some
liquid that has the same refractive index as glass. The prof. put a
small beaker inside a bigger beaker and poured this liquid into the big
beaker, and when the small beaker got covered up, it disappeared! I
don't remember if that was CS2 or not. )-;

No, in any case it's usually not sufficiently colourless. Spit! I can't
remember what the liquid actually is.

Imagine my surprise! Wesson oil! =:-O

http://physics.usc.edu/demolab/o/o1/o1_8.html

But, the one I saw, the liquid was colorless, and watery rather than oily.

Cheers!
Rich

 

[John Woodgate]

I read in sci.electronics.design that Rich Grise <richgrise@example.net>
wrote (in <pan.2005.02.19.20.44.28.8003@example.net&gt about 'UV lamp
question for ozone generation...', on Sat, 19 Feb 2005:

Imagine my surprise! Wesson oil! =:-O

http://physics.usc.edu/demolab/o/o1/o1_8.html

Well, there are undoubtedly several liquids that match different types
of glass.

But, the one I saw, the liquid was colorless, and watery rather than
oily.

Yes, the one I have in mind is a specific compound, but it's not a
common organic reagent.
--
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

 

[Lord Garth]

"RST Engineering (jw)" <jim@rstengineering.com> wrote in message
news:111hars36bo1t7a@corp.supernews.com...

Lordy, Outlook Express makes you change the font in no less than THREE
places in order to force messages to Courier. THe default fixed width,
the
default proportional width, and the little checkbox on the "advanced" tab
to
default all incoming messages to the default settings.

Windoze does it again.

Thanks for the help, Rich...

Jim

If you use OE and the font is not set to default to a fixed width font, you
can
select 'view' then move down to 'text size' then move to 'fixed' to see it
on the
ASCII art on the fly.

 

[Watson A.Name - \"Watt Su]

"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:g0nd1197fcaof5kb1je9i90vpe1irqdgbs@4ax.com...

On Sat, 19 Feb 2005 03:31:40 GMT, LEDMan@3v.invalid (LED Man) wrote:

Looking to drive a white superbright led (1-4) from 1.5v to 2.5v
battery, led requires 3.3v @ 20ma, is there a suitable small circuit,
or
single chip device

An NPN, a 1.5V AA battery, two resistors, a capacitor, a diode and a
simple,
hand-wound threaded toroidal. D2 can be a diode-connected 2N3904, a
1N4148, or
a Schottky like a 1N5817-1N5819.

V+ V+ V+
| | |
| | |
| )|. .|( (about 50" of
| )| |( magnet wire
| )| T1 |( for both
| + )| |( windings)
--- | |
- B1 | | D2 R2
--- \ +---|>|---+---/\/\---,
- / R1 | | 220 |
| \ 2200 | | |
| / | | |
| | |/c Q1 | --- ~
| '------| 2N3904 --- C1 \ / ~
| |>e --- 100uF --- LED
| (B1 > 1V) | | |
| | | |
gnd gnd gnd gnd

It will drain a AA battery fairly completely, before quitting.

I really despise those who suggest that the 2N3904 is capable of doing
this job adequately. With that wimpy transistor, you will be lucky to
get enough current to power the LED at 8mA. Use a 2N4401 or the BC337.
Or if you want to get a lot more current, try the 2SD965 or NTE11. If
you can get some disposable flash cameras from your neighborhood
drugstore or photo shop, the flash inverter uses this kind of
transistor, and makes a great source for free transistors.

The above circuit is okay, but since the LED _is_ a diode, you don't
need the D2 and C2 filter cap, just connect the LED across the emitter
and collector. And R1 will have to be lower, probably 1k, if you use
something better than the 2N3904. The 2N3904 won't cut it with even a
470, it'll just get hot and poof. And whatthe hell is R2 there for?
That's just wasting power and ruining the efficiency!

> Jon

 

[Jonathan Kirwan]

On Sun, 20 Feb 2005 12:15:44 -0800, "Watson A.Name - \"Watt Sun, the Dark
Remover\"" <NOSPAM@dslextreme.com> wrote:

I really despise those who suggest that the 2N3904 is capable of doing
this job adequately.

I'm actually using one and it's pretty decent on a white LED. If you have to
despise me for it, I guess I can only hope to make it up some time later on.
(I'm just a modest hobbyist, so I take corrections from just about anyone.)

With that wimpy transistor, you will be lucky to
get enough current to power the LED at 8mA. Use a 2N4401 or the BC337.

Fair enough.

Or if you want to get a lot more current, try the 2SD965 or NTE11. If
you can get some disposable flash cameras from your neighborhood
drugstore or photo shop, the flash inverter uses this kind of
transistor, and makes a great source for free transistors.

The above circuit is okay, but since the LED _is_ a diode, you don't
need the D2 and C2 filter cap, just connect the LED across the emitter
and collector.

Actually, that's what I did before. In fact, I had no R2, as well. I just
added those for tinkering, at some point, to smooth the pulses through the LED.

And R1 will have to be lower, probably 1k, if you use
something better than the 2N3904. The 2N3904 won't cut it with even a
470, it'll just get hot and poof. And whatthe hell is R2 there for?
That's just wasting power and ruining the efficiency!

Yes, I started out just as you say. Works just fine. This is what I'd started
with:

V+ V+ V+
| | |
| | |
| )|. .|( (about 50" of
| )| |( magnet wire
| )| T1 |( for both
| + )| |( windings)
--- | |
- B1 | |
--- \ +---------,
- / R1 | |
| \ | |
| / | |
| | |/c Q1 --- ~
| '------| NPN \ / ~
| |>e --- LED
| (B1 > 1V) | |
| | |
gnd gnd gnd
(can be connected to V+, as well)

Threading up the transformer on a tiny toroid is dead easy, too. By the way,
I've picked up some small packages of them from a local electronics supply
house, but I've not found a good web site that has them. Do you know of a good
source for various ferrite toroids?

Jon

 

Racer wrote:

Dear All,
Does anyone have an idea for a low
voltage threshold circuit that switches
from its Low (Off) to High (On) state (or vice
versa) upon an input voltage reaching a
fixed predetermined low voltage level of
.... say 0.658 volts?
The design must disregard all input
voltage variations (DC and/or AC) until
the threshold ( or higher ) voltage of
0.658 volts is reached and at this point,
switch On and remain On until the input
voltage drops below 0.658 volts.
The output will be resistive and switch
between zero volt and the supply voltage
( about 4.5 volts to 12 volts )
I think one could call the circuit a "low
voltage threshold switch".
The simpler the design and lower the
component count, the better.
Ideas ..... anyone? .............

You've just described a comparator - the National Semiconductor LM393
is simple example of the device

http://cache.national.com/ds/LM/LM193.pdf

where you have connected your unknown voltage to one input and a 0.685V
reference voltage to the other.

The output isn't normally described as resistive - it is the collector
of a transistor whose emitter is connected to the negative supply pin
of the comparator, which is normally connected to 0V. This sort of
"open collector" output is typical for cheap comparators.

The somewhat more expensive LM311

http://cache.national.com/ds/LM/LM111.pdf

has a more flexible version of this output stage.

There are a great many other comparators available - if you tell us a
bit more about what you are trying to do, we can probably be a lot more
helpful.

This is a pretty elementary question, and probably should have been
posted on sci.electronics.basics.

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

 

[Don Lancaster]

bill.sloman@ieee.org wrote:

Racer wrote:

Dear All,
Does anyone have an idea for a low
voltage threshold circuit that switches
from its Low (Off) to High (On) state (or vice
versa) upon an input voltage reaching a
fixed predetermined low voltage level of
.... say 0.658 volts?
The design must disregard all input
voltage variations (DC and/or AC) until
the threshold ( or higher ) voltage of
0.658 volts is reached and at this point,
switch On and remain On until the input
voltage drops below 0.658 volts.
The output will be resistive and switch
between zero volt and the supply voltage
( about 4.5 volts to 12 volts )
I think one could call the circuit a "low
voltage threshold switch".
The simpler the design and lower the
component count, the better.
Ideas ..... anyone? .............


You've just described a comparator - the National Semiconductor LM393
is simple example of the device

http://cache.national.com/ds/LM/LM193.pdf

where you have connected your unknown voltage to one input and a 0.685V
reference voltage to the other.

The output isn't normally described as resistive - it is the collector
of a transistor whose emitter is connected to the negative supply pin
of the comparator, which is normally connected to 0V. This sort of
"open collector" output is typical for cheap comparators.

The somewhat more expensive LM311

http://cache.national.com/ds/LM/LM111.pdf

has a more flexible version of this output stage.

There are a great many other comparators available - if you tell us a
bit more about what you are trying to do, we can probably be a lot more
helpful.

This is a pretty elementary question, and probably should have been
posted on sci.electronics.basics.

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

When you are done designing this circuit, you'll find that it isusually
NOT a good idea to use the same up and down threshold.

Instead you'll want to add a dead band with slight to moderate hysteresis.
This can be done by feedback from the comparator level to raise the
input threshold on an upevent and lower it on a downevent.


--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Tim Zimmerman]

"Lord Garth" <LGarth@Tantalus.net> wrote in message news:VW2Sd.14924$D34.10156@newssvr12.news.prodigy.com...

If you use OE and the font is not set to default to a fixed width
font, you can select 'view' then move down to 'text size' then move
to 'fixed' to see it on the ASCII art on the fly.

Excellent tip.

If the reason we use ASCII Schematics is because of the text based
USENET. Then why do some websites still use ASCII Schematics?

 

[Lord Garth]

"Tim Zimmerman" <Z@UCBerkeley.edu> wrote in message
news:8KASd.6432$Pz7.690@newssvr13.news.prodigy.com...

"Lord Garth" <LGarth@Tantalus.net> wrote in message
news:VW2Sd.14924$D34.10156@newssvr12.news.prodigy.com...

If you use OE and the font is not set to default to a fixed width
font, you can select 'view' then move down to 'text size' then move
to 'fixed' to see it on the ASCII art on the fly.

Excellent tip.

If the reason we use ASCII Schematics is because of the text based
USENET. Then why do some websites still use ASCII Schematics?

Leftover source material from the days of telnet perhaps...

 

[Michael A. Terrell]

Robert Monsen wrote:

BTW, I thought it would be pretty cool to build a lissajous pattern
generator for my oscilloscope. The one they had at the exploratorium
allowed adjustments with an accuracy of 0.01 Hz in the oscillators for X
and Y. I was wondering if there was a simple analog circuit they were
using to do that, or whether it was digitally created using a
microprocessor... The frequency range IIRC was between 0 and 400 Hz.

--
Regards,
Robert Monsen

Sounds like a good application for a couple DDS chips and low pass
filters.

--
Beware of those who suffer from delusions of adequacy!

Michael A. Terrell
Central Florida

 

[Racer]

On Mon, 21 Feb 2005 09:56:39 -0700, Don Lancaster <don@tinaja.com>
wrote:

bill.sloman@ieee.org wrote:
Racer wrote:

Dear All,
Does anyone have an idea for a low
voltage threshold circuit that switches
from its Low (Off) to High (On) state (or vice
versa) upon an input voltage reaching a
fixed predetermined low voltage level of
.... say 0.658 volts?
The design must disregard all input
voltage variations (DC and/or AC) until
the threshold ( or higher ) voltage of
0.658 volts is reached and at this point,
switch On and remain On until the input
voltage drops below 0.658 volts.
The output will be resistive and switch
between zero volt and the supply voltage
( about 4.5 volts to 12 volts )
I think one could call the circuit a "low
voltage threshold switch".
The simpler the design and lower the
component count, the better.
Ideas ..... anyone? .............


You've just described a comparator - the National Semiconductor LM393
is simple example of the device

http://cache.national.com/ds/LM/LM193.pdf

where you have connected your unknown voltage to one input and a 0.685V
reference voltage to the other.

The output isn't normally described as resistive - it is the collector
of a transistor whose emitter is connected to the negative supply pin
of the comparator, which is normally connected to 0V. This sort of
"open collector" output is typical for cheap comparators.

The somewhat more expensive LM311

http://cache.national.com/ds/LM/LM111.pdf

has a more flexible version of this output stage.

There are a great many other comparators available - if you tell us a
bit more about what you are trying to do, we can probably be a lot more
helpful.

This is a pretty elementary question, and probably should have been
posted on sci.electronics.basics.

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


When you are done designing this circuit, you'll find that it isusually
NOT a good idea to use the same up and down threshold.

Instead you'll want to add a dead band with slight to moderate hysteresis.
This can be done by feedback from the comparator level to raise the
input threshold on an upevent and lower it on a downevent.

Yes, thnx Don .... the hysteresis band will be set to...... say
10 - 15 mV.

To Bill Sloman..... thanks for your pointers and links.

Now, on to the next question ........ ;-p
What simple circuit would you consider using to interface
the output of the comparator to switch one Led or the other
depending on whether the output was Low or High. At no
point should the two Leds be lit even at low luminance? It
would have to be one or the other.
A low powered mechanical relay would do the trick but
what about some simple semiconductor arrangement.
Again, low component count and cost is a factor.

Thanks again Don and Bill for you for your responses.

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

_____________________________________________

 

[Chris]

Racer wrote:

On Mon, 21 Feb 2005 09:56:39 -0700, Don Lancaster <don@tinaja.com
wrote:

bill.sloman@ieee.org wrote:
Racer wrote:

Dear All,
Does anyone have an idea for a low
voltage threshold circuit that switches
from its Low (Off) to High (On) state (or vice
versa) upon an input voltage reaching a
fixed predetermined low voltage level of
.... say 0.658 volts?
The design must disregard all input
voltage variations (DC and/or AC) until
the threshold ( or higher ) voltage of
0.658 volts is reached and at this point,
switch On and remain On until the input
voltage drops below 0.658 volts.
The output will be resistive and switch
between zero volt and the supply voltage
( about 4.5 volts to 12 volts )
I think one could call the circuit a "low
voltage threshold switch".
The simpler the design and lower the
component count, the better.
Ideas ..... anyone? .............


You've just described a comparator - the National Semiconductor
LM393
is simple example of the device

http://cache.national.com/ds/LM/LM193.pdf

where you have connected your unknown voltage to one input and a
0.685V
reference voltage to the other.

The output isn't normally described as resistive - it is the
collector
of a transistor whose emitter is connected to the negative supply
pin
of the comparator, which is normally connected to 0V. This sort of
"open collector" output is typical for cheap comparators.

The somewhat more expensive LM311

http://cache.national.com/ds/LM/LM111.pdf

has a more flexible version of this output stage.

There are a great many other comparators available - if you tell
us a
bit more about what you are trying to do, we can probably be a lot
more
helpful.

This is a pretty elementary question, and probably should have
been
posted on sci.electronics.basics.

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


When you are done designing this circuit, you'll find that it
isusually
NOT a good idea to use the same up and down threshold.

Instead you'll want to add a dead band with slight to moderate
hysteresis.
This can be done by feedback from the comparator level to raise the
input threshold on an upevent and lower it on a downevent.

Yes, thnx Don .... the hysteresis band will be set to...... say
10 - 15 mV.

To Bill Sloman..... thanks for your pointers and links.

Now, on to the next question ........ ;-p
What simple circuit would you consider using to interface
the output of the comparator to switch one Led or the other
depending on whether the output was Low or High. At no
point should the two Leds be lit even at low luminance? It
would have to be one or the other.
A low powered mechanical relay would do the trick but
what about some simple semiconductor arrangement.
Again, low component count and cost is a factor.

Thanks again Don and Bill for you for your responses.

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

_____________________________________________

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.

By the way, basic uses of comparators are covered in Mr. Lancaster's
CMOS Cookbook, in Chapter 7. It's available from the library, Amazon,
and also direct from Mr. Lancaster's Guru's Lair:

http://www.tinaja.com/

You also might want to go to the National Semiconductor website and
look at the data sheet for the comparator, as well as an appnote
written for that IC:

http://www.national.com/pf/LM/LM393.html#Datasheet
http://www.national.com/an/AN/AN-74.pdf

Good luck
Chris

 

[Robert Monsen]

Michael A. Terrell wrote:

Robert Monsen wrote:

BTW, I thought it would be pretty cool to build a lissajous pattern
generator for my oscilloscope. The one they had at the exploratorium
allowed adjustments with an accuracy of 0.01 Hz in the oscillators for X
and Y. I was wondering if there was a simple analog circuit they were
using to do that, or whether it was digitally created using a
microprocessor... The frequency range IIRC was between 0 and 400 Hz.

--
Regards,
Robert Monsen


Sounds like a good application for a couple DDS chips and low pass
filters.

I picked up a cheapo signal generator chip from futurlec. It's an
ICL8038, which is a VCO which can generate sine waves, triangle waves,
and square waves between 0.1Hz and about 100kHz. Unfortunately, it's
squirrly and sensitive to temperature. Also, adjusting the duty cycle
seriously messes with the frequency. In order to fix this, I then wrote
a program for a PIC that measures the squarewave frequency, and controls
the VCO input using an SPI DAC I sampled from microchip. It's frequency
is thus now as stable and accurate as the PIC clock, which is derived
from a 20MHz crystal, even when changing the duty cycle.

To generate the lissajous patterns, I set up the 3011B to output a 500
Hz signal on the X channel, and use the ICL8038 on the Y channel of my
scope. I then vary the frequency up or down using simple controls to the
PIC. I use my sears multimeter, which has a 4.5 digit frequency mode, to
view the frequency of the PIC. It would be easy to build an LCD display
for the thing, but the multimeter works well enough.

--
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.

 

[Robert Monsen]

LED Man wrote:

Looking for a very simple (Newby) 5v to 12v circuit, or device, low
cost, to run 120 ma 12v led off 5-6v

TIA

You need a boost circuit.

You can buy DC-DC converters for this kind of application, but they may
violate your 'low cost' requirement. You can probably get them surplus.
I know I've seen them at halted specialties in san jose for a few bucks.

Here is a web page that describes the basics, if you want to try to
build your own:

http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-DC/converter.shtm

You can also use switched capacitor circuits to do this, but it's hard
to get 120mA from one of these.

--
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.

 

Racer wrote:

On Mon, 21 Feb 2005 09:56:39 -0700, Don Lancaster <don@tinaja.com
wrote:

bill.sloman@ieee.org wrote:

<snip>

Now, on to the next question ........ ;-p
What simple circuit would you consider using to interface
the output of the comparator to switch one Led or the other
depending on whether the output was Low or High. At no
point should the two Leds be lit even at low luminance? It
would have to be one or the other.
A low powered mechanical relay would do the trick but
what about some simple semiconductor arrangement.
Again, low component count and cost is a factor.

Thanks again Don and Bill for you for your responses.

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.

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

 

[Racer]

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

Hello Chris, thank you for responding.

Hi, Racer. Let's recap the bidding. You want to switch a digital
output (logic 1, 0) at around 0.658V analog input voltage.
Yes

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.
True again.....

You now want to have something
inexpensive which will light one of two LEDs depending on the input
voltage.
Spot On !

How does "free" sound?
Huh? ..... i lost you there !? ......

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.

By the way, basic uses of comparators are covered in Mr. Lancaster's
CMOS Cookbook, in Chapter 7. It's available from the library, Amazon,
and also direct from Mr. Lancaster's Guru's Lair:

http://www.tinaja.com/

You also might want to go to the National Semiconductor website and
look at the data sheet for the comparator, as well as an appnote
written for that IC:

http://www.national.com/pf/LM/LM393.html#Datasheet
http://www.national.com/an/AN/AN-74.pdf

Good luck
Chris

I really don't know how to thank you for taking so much
time and trouble to explain .....
Yours is an elegant solution if it works - It meets all the
requirements of simple circuitry, low component count,
low cost and not requiring a +/- VCC supply...... in a word,
...... perfect !!
Perhaps you shoul;d consider writing a book for dummies
like myself ! ........

Thanks so much Chris .......

/Racer

 

[Racer]

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

Hello Chris, thank you for responding.

Hi, Racer. Let's recap the bidding. You want to switch a digital
output (logic 1, 0) at around 0.658V analog input voltage.
Yes

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.
True again.....

You now want to have something
inexpensive which will light one of two LEDs depending on the input
voltage.
Spot On !

How does "free" sound?
Huh? ..... i lost you there !? ......

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.

By the way, basic uses of comparators are covered in Mr. Lancaster's
CMOS Cookbook, in Chapter 7. It's available from the library, Amazon,
and also direct from Mr. Lancaster's Guru's Lair:

http://www.tinaja.com/

You also might want to go to the National Semiconductor website and
look at the data sheet for the comparator, as well as an appnote
written for that IC:

http://www.national.com/pf/LM/LM393.html#Datasheet
http://www.national.com/an/AN/AN-74.pdf

Good luck
Chris

I really don't know how to thank you for taking so much
time and trouble to explain .....
Yours is an elegant solution if it works - It meets all the
requirements of simple circuitry, low component count,
low cost and not requiring a +/- VCC supply...... in a word,
...... perfect !!
Perhaps you shoul;d consider writing a book for dummies
like myself ! ........

Thanks so much Chris .......

/Racer