Can you help design this circuit .....

[Racer]

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? .............

 

[Pig Bladder]

On Mon, 21 Feb 2005 13:41:50 +0800, 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? .............

Go to the index of your textbook and look up "comparator".
--
The Pig Bladder From Uranus, Still Waiting for
Some Hot Babe to Ask What My Favorite Planet Is.

 

[www.interfacebus.com]

Sounds like a homework problem

 

Trying to tell someone about hysterisis when they don't know about
comparators is somewhat counter-productive.

Until we know what Racer is actually trying to do, more detailed advice
is probably wasted - and in any event if Racer has a real talent for
electronics, that sort of information could be mined from the LM193
datasheet, whose URL I posted.

The next time you want tell somebody about hysterisis, think about
being more explicit in describing how the (positive) feedback is
actually done - a phrase like "a high value resistor between the
comparator output and the non-inverting input" might not go amiss.

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

 

[Racer]

On 21 Feb 2005 08:34:23 -0800, "www.interfacebus.com"
<ldavis8@cfl.rr.com> wrote:

Sounds like a homework problem

Umm.... perhaps it is! .......

So why don't _you_ go ahead and design a UV laser?
...... jus joking ...... hehehe

 

[Michael A. Terrell]

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.

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

Michael A. Terrell
Central Florida

 

[Chris]

John Fields wrote:

---
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

Mr. Fields is correct on all counts. I'd assume you'd want a 10-turn
pot to tweak your voltage. The resistor ratio for the hysteresis was
obiously incorrect -- modified below. Also, the output open collector
transistor of the LM393 is weak, and tends to have a high saturation
voltage (logic low level) when it's on. You can remedy that by using
transistors to drive the LEDs like this (view in fixed font or M$
Notepad):

` 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

 

[Racer]

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!
/Racer

 

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.

Since I was a foundation subscriber to Byte (thanks to Dan Fylstra who
got interested in my wife - some years before we finally married - when
she was doing at post-doc at MIT and Dan was involved in setting up
Byte) I've known about Don Lancaster for more than 25 years. His
Gurugrams might suggest that he'd see a private e-mail as an
opportunity to get some consulting, but his books are popular enough
that he might get so many private e-mails that this wouldn't be
practical.

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

You seem to be suffering from such a delusion.

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

 

[Michael A. Terrell]

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.

Since I was a foundation subscriber to Byte (thanks to Dan Fylstra who
got interested in my wife - some years before we finally married - when
she was doing at post-doc at MIT and Dan was involved in setting up
Byte) I've known about Don Lancaster for more than 25 years. His
Gurugrams might suggest that he'd see a private e-mail as an
opportunity to get some consulting, but his books are popular enough
that he might get so many private e-mails that this wouldn't be
practical.

I was a charter subscriber to BYTE, and supposedly had a lifetime
subscription till Wayne Green sold the magazine and they refused to
owner the lifetime subscription I paid for. I subscribed as soon as he
wrote about creating BYTE in "73 Magazine" The lifetime subscriptions
were announced when the first year ran out so I paid the $150 and got
screwed. Of course, BYTE isn't worth buying anymore so I really don't
care.

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

You seem to be suffering from such a delusion.

Not at all, but I am now fully disabled from a laundry list of
physical problems and I'm to the point I don't care what you, or several
people on the different newsgroups think. Keep making your jabs and
look as silly as you want, no one cares.

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

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

Michael A. Terrell
Central Florida

 

[Fred Bloggs]

Chris wrote:

John Fields wrote:

---
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


Mr. Fields is correct on all counts. I'd assume you'd want a 10-turn
pot to tweak your voltage. The resistor ratio for the hysteresis was
obiously incorrect -- modified below. Also, the output open collector
transistor of the LM393 is weak, and tends to have a high saturation
voltage (logic low level) when it's on. You can remedy that by using
transistors to drive the LEDs like this (view in fixed font or M$
Notepad):

` 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

You're not going to have enough bias current for the '385 at Vdd=5V when
the 1K reference pot consumes 1.24mA. And the LED currents range over
~(12-2)/(5-2) or > 3:1 ratio with Vdd. So some adjustments will have to
made for Vdd to operate over the specified 5-12V range. Maybe you could
re-arrange the reference ckt to produce both a Vthreshold for the
comparison and a current source for the LEDs like so ( simplified):
View in a fixed-width font such as Courier.

.
. Vdd 5-12V
. o----o---o--------o--------o--o---------o------o---------.
. | | | | | | | | |
. | | | ---0.22u | | | | |
. | | ---33n --- | .-. | .-. |
. | | --- | | | |100K | | |100K |
. | | | === | | | | | | |
. | | .-. GND | '-' | '-' |
. | | | |150 | | ___ |/e T4 | ___ |/e
. | | | | | o-|___|-|pnp o-|___|-| pnp
. .-. | '-' | | 10K |\ | 10K |\
. 1.5K| | | | ~~ | | | | |
. | | | o-----|<|---------|--|---------' | T5|
. '-' | | LED | | | |
. | |/ T3 | ~~ | | | |
. o--|npn o-----|<|---------|--|----------------|---------'
. | |\e | LED | | |
. | | | | | |
. \| | |/ | | |
. T1 npn|--o-|npn T2 |\| | LM393 |
. e/| |\e Vin >-----|-\ | |\ |
. | | | >-o-----------|-\ |
. | | ,---|+/ | | >-'
. | | V -> | |/ | ,----|+/
. | | th | | | |/|
. |(1.24V) | | | | |
. o--------|------o----|---------------' |
. | | | | | |
. | .-. .-. | ___ | |
. | 120| | 1K| |<--o--|___|-' |
. LM385 /-/ | | | | 1M |
. ^-. '-' '-' |
. | | | | |
. o-o------o------o---------------------------'
. |
. ===
. GND
.

 

[Chris]

Robert Monsen wrote:

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

<snip description of circuit action>

--
Regards,
Robert Monsen

And you know what -- your circuit here is probably closer to what the
OP actually needs, too. <g>

Thanks
Chris

 

[Racer]

On Sat, 26 Feb 2005 07:29:33 GMT, Fred Bloggs <nospam@nospam.com>
wrote:

Racer wrote:
...... snip .....

Hi Fred ! Wow! .... The circuit is becoming quite complex
with each improvement.......
Perhaps I could use a Siemens "TCA105" 6 pin dil IC to
acheive the same result ..... no?
Thanks,
/Racer

I don't see why not. Where is that input coming from and how critical is
that 0.658V threshold? Is it from a temperature sensing thermistor and
what is the impedance of the circuit in which the signal originates?

Actually, the circuit is supposed to be used as a standard
independent unit to which could be interfaced various
kinds of output from a wide range of sensors for
temperature, RPM, light intensity, level, voltage, current,
power, etc etc .... I think you get the picture.
The threshold of 0.658V ( at very low current as the trigger
to minimise loading and ensure the voltage was slightly
above the forward voltage of most transistors ) was provided
so this unit, when finally fabricated, would be able to function even
when tight tolerances are required.
tq
=====================================================

Dear All

I don't know who here sent me the e-mail advising that I
take a look at the Siemens " TCA105 " as a low cost
solution (but minus the audio stage ) - Whoever it was,
I'd like to say a BIG THANK YOU!!

I have tried to source the data and application sheet but
managed to get just one ...... hope the chip has not been
discontinued.

Feedback on your views or advice about links on the use
of this Siemens" TCA105" IC would be appreciated.

Thank you everyone who contributed with their expertise.

/Racer

 

[Racer]

On Fri, 25 Feb 2005 14:07:02 -0800, Robert Monsen
<rcsurname@comcast.net> wrote:

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


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

Thank you Robert ! .....

Is the above link your web site?

/Racer

 

[Racer]

On Sat, 26 Feb 2005 14:37:58 GMT, Fred Bloggs <nospam@nospam.com>
wrote:

Racer wrote:


Actually, the circuit is supposed to be used as a standard
independent unit to which could be interfaced various
kinds of output from a wide range of sensors for
temperature, RPM, light intensity, level, voltage, current,
power, etc etc .... I think you get the picture.
The threshold of 0.658V ( at very low current as the trigger
to minimise loading and ensure the voltage was slightly
above the forward voltage of most transistors ) was provided
so this unit, when finally fabricated, would be able to function even
when tight tolerances are required.

That makes no sense.

Well Fred, with my poor command of English and
an even poorer appreciation of electronics, that's
the best I can do .......

/Racer

 

[Fred Bloggs]

John Fields wrote:

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

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

 

[John Fields]

On Sat, 26 Feb 2005 12:02:34 -0600, John Fields
<jfields@austininstruments.com> wrote:

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.

---
Pull-up and symmetry fix here:

news:deq121t2u5b754tctmk3f8ov8dm4n4vh4g@4ax.com

--
John Fields

 

[Terry Pinnell]

John Fields <jfields@austininstruments.com> wrote:

Pull-up and symmetry fix here:

news:deq121t2u5b754tctmk3f8ov8dm4n4vh4g@4ax.com

John: You used to give a Subject when referencing posts to
alt.binaries.schematics.electronic. I've recently split my news
reading so that all binary groups are in another 'instance' of my
newsreader. (Agent is still incapable of handling multiple servers,
although still my preferred email/news reader). So I can no longer
simply d-click a news: reference to get to your post. It's no big deal
(I can find it pretty quickly), but I'd appreciate your returning to
including the Subject and maybe date please.

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[John Fields]

On Sun, 27 Feb 2005 11:02:19 +0000, Terry Pinnell
<terrypinDELETE@THESEdial.pipex.com> wrote:

John Fields <jfields@austininstruments.com> wrote:


Pull-up and symmetry fix here:

news:deq121t2u5b754tctmk3f8ov8dm4n4vh4g@4ax.com

John: You used to give a Subject when referencing posts to
alt.binaries.schematics.electronic. I've recently split my news
reading so that all binary groups are in another 'instance' of my
newsreader. (Agent is still incapable of handling multiple servers,
although still my preferred email/news reader). So I can no longer
simply d-click a news: reference to get to your post. It's no big deal
(I can find it pretty quickly), but I'd appreciate your returning to
including the Subject and maybe date please.

---
Sure, no problem.

I don't understand why you can't just click on the URL, though, I'm
also using Agent and it works for me. Version 2.0, though. Maybe
that's it?

--
John Fields