Wanted: A nice puls for an opto coupler

[Frank Bemelman]

Okay, the request is a circuit that pulses an opto coupler, briefly
and just once. It should do so, everytime it is powered up. Power
is 9V.

An IC would be fine too. Anyway, I fiddled this:


+9V ----------.-----.-----.------------.-----------
| | | | |
| | | | .-.
| | | DIODE - | |470 (OPTO)
| 220n| | ^ | |
| --- >| ___ | + #|- '.'
| --- |--|___|---'----#|----|
| | /| 560K #| |
.-. | | 1uF |
| | | | PNP |
10K | | | | |
'-' | | |
| | | ___ |/
| o-----o----------|___|------| NPN
| | 1000 |>
| | |
| - .
| ^ DIODE |
| | |
| | |
| | |
GND-----------'-----'-----------------------------'
created by Andy´s ASCII-Circuit v1.21 Beta www.tech-chat.de


Any improvements possible? Win is of course not allowed to
participate, because he is much too clever.


--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

 

[Joerg]

Hi Genome,

There used to also be a "CMOS cook book", similar to the TTL cook book
but I never had a copy myself. That had tons of tricks with CD chips in
there. An application note that might interest you would be National's
old AN-88. It explains the use of CMOS logic chips (not Schmitts, of
course) for linear amplification purposes. I believe it's not on their
server anymore but probably TI, ON Semi or Fairchild have similar app notes.

This old 4000 logic series is marvelous when the task is to drive some
circuitry to rock bottom cost. It also enjoys a great longevity and
might even surpass the VW Beatle since they recently came out with tiny
packages a little over half the SO footprint.

Regards, Joerg

http://www.analogconsultants.com

 

[legg]

On Tue, 19 Oct 2004 00:42:31 +0200, "Frank Bemelman"
<f.bemelmanx@xs4all.invalid.nl> wrote:

Okay, the request is a circuit that pulses an opto coupler, briefly
and just once. It should do so, everytime it is powered up. Power
is 9V.

An IC would be fine too. Anyway, I fiddled this:


+9V ----------.-----.-----.------------.-----------
| | | | |
| | | | .-.
| | | DIODE - | |470 (OPTO)
| 220n| | ^ | |
| --- >| ___ | + #|- '.'
| --- |--|___|---'----#|----|
| | /| 560K #| |
.-. | | 1uF |
| | | | PNP |
10K | | | | |
'-' | | |
| | | ___ |/
| o-----o----------|___|------| NPN
| | 1000 |
| | |
| - .
| ^ DIODE |
| | |
| | |
| | |
GND-----------'-----'-----------------------------'
created by AndyŤs ASCII-Circuit v1.21 Beta www.tech-chat.de


Any improvements possible? Win is of course not allowed to
participate, because he is much too clever.

You should include EB resistors of 10K or less to ensure against
spradic flashing wth elevated temperature. I'm not sure how you'd work
this into the pnp portion, while maintaining the RC time constant.

I don't suppose supply noise is likely?

RL

 

[Fred Bloggs]

Frank Bemelman wrote:

Okay, the request is a circuit that pulses an opto coupler, briefly
and just once. It should do so, everytime it is powered up. Power
is 9V.

An IC would be fine too. Anyway, I fiddled this:


+9V ----------.-----.-----.------------.-----------
| | | | |
| | | | .-.
| | | DIODE - | |470 (OPTO)
| 220n| | ^ | |
| --- >| ___ | + #|- '.'
| --- |--|___|---'----#|----|
| | /| 560K #| |
.-. | | 1uF |
| | | | PNP |
10K | | | | |
'-' | | |
| | | ___ |/
| o-----o----------|___|------| NPN
| | 1000 |
| | |
| - .
| ^ DIODE |
| | |
| | |
| | |
GND-----------'-----'-----------------------------'
created by Andy´s ASCII-Circuit v1.21 Beta www.tech-chat.de


Any improvements possible? Win is of course not allowed to
participate, because he is much too clever.

Depends how that 9V is applied- you say just one pulse- so the power
switch must be debounced- and if that is the case none of the circuits
so far work- you need to qualify the output pulse by not initiating it
until power is up and stays up. A CMOS 555 would be best because the
ultra-high input impedance allows you to use smallest possible filter
capacitor.