# Short +ve pulses, simplest solution?

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Terry Pinnell
Guest

Thu Aug 16, 2018 3:45 pm

The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

George Herold
Guest

Thu Aug 16, 2018 4:45 pm

On Thursday, August 16, 2018 at 10:41:50 AM UTC-4, Terry Pinnell wrote:
Quote:
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

The two states are low resistance in the day with sunlight,
and high resistance at night?

Some comparator with a lot of hysteresis maybe. ...
Maybe a low pass filter in front?

George H.

Terry Pinnell
Guest

Fri Aug 17, 2018 7:45 am

George Herold <gherold_at_teachspin.com> wrote:

Quote:
On Thursday, August 16, 2018 at 10:41:50 AM UTC-4, Terry Pinnell wrote:
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

The two states are low resistance in the day with sunlight,
and high resistance at night?

Some comparator with a lot of hysteresis maybe. ...
Maybe a low pass filter in front?

George H.

Thanks George. I've unearthed my old files and your approach appears to
be the one I took. The circuit illustrated here

https://www.dropbox.com/s/r2b3lqrmpaelh4k/CurtainController-LDR-2.jpg?raw=1

was changed (but not re-drawn) a decade or so ago, but it's still
essentially correct. As mentioned, the LDR is not now measuring the
external light (that proved problematic) but is enclosed, flush against
a neon indicator lamp that is on/off at set times of the 24 hour day. So
my DMM measures the resistance across the LDR as roughly 8M at night and
8K during the day.

Note that, contrary to what I said in my initial post, the circuit I
want is NOT to toggle the curtain's state, but to separately open
(morning) or close them (night).

Still trying to isolate the cause of the fault: repeated opening and
closing!

Terry, East Grinstead, UK

ZOT
Guest

Fri Aug 17, 2018 10:45 am

Le 16/08/2018 16:41, Terry Pinnell a écrit :
Quote:
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

Well done! but how are you moving the curtains, pully, cables? how are
all this arranged?
I am building one but if I can make the motor truning, I don't find how
to go further.
André

Jasen Betts
Guest

Fri Aug 17, 2018 11:45 am

On 2018-08-16, Terry Pinnell <me_at_somewhere.invalid> wrote:
Quote:
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

XOR gate with delayed feedback on the other input.

Or this thing.

+--------+--- 0V
| |
[R] [R]
| |
+->|-----|-----+--- out
| | |
=== | |
| +->|--+
| |
| ===
in | |
--|>o--+---|>o--+

--
Øª

ZOT
Guest

Fri Aug 17, 2018 12:45 pm

Le 17/08/2018 13:13, default a écrit :
Quote:
On Fri, 17 Aug 2018 11:43:59 +0200, ZOT <pasmoi_at_pasici.us> wrote:

Le 16/08/2018 16:41, Terry Pinnell a écrit :
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

Well done! but how are you moving the curtains, pully, cables? how are
all this arranged?
I am building one but if I can make the motor truning, I don't find how
to go further.
André

I did something with heavy drapes on a longish transverse rod. A loop
around a 3" plastic pulley mounted on a gear motor provided enough
tension, with the motor and pivoting bracket providing a weight to
keep tension on the line more or less constant. (compensates for
stretch in the nylon line because it gets slack when the humidity is
high)

I used a disk positioned on the line to work a microswitch for "end of
travel," but a stepper motor or current sensing is probably a better
way to do it.

default
Guest

Fri Aug 17, 2018 12:45 pm

On Fri, 17 Aug 2018 11:43:59 +0200, ZOT <pasmoi_at_pasici.us> wrote:

Quote:
Le 16/08/2018 16:41, Terry Pinnell a écrit :
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

Well done! but how are you moving the curtains, pully, cables? how are
all this arranged?
I am building one but if I can make the motor truning, I don't find how
to go further.
André

I did something with heavy drapes on a longish transverse rod. A loop
around a 3" plastic pulley mounted on a gear motor provided enough
tension, with the motor and pivoting bracket providing a weight to
keep tension on the line more or less constant. (compensates for
stretch in the nylon line because it gets slack when the humidity is
high)

I used a disk positioned on the line to work a microswitch for "end of
travel," but a stepper motor or current sensing is probably a better
way to do it.

Terry Pinnell
Guest

Fri Aug 17, 2018 10:45 pm

ZOT <pasmoi_at_pasici.us> wrote:

Quote:
Le 16/08/2018 16:41, Terry Pinnell a écrit :
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

Well done! but how are you moving the curtains, pully, cables? how are
all this arranged?
I am building one but if I can make the motor truning, I don't find how
to go further.

Hi André,

Back in 2004 I explored a bunch of design ideas but here's a rough
outline of the finished thing:

https://www.dropbox.com/s/pyg6eapmctd6pcv/CurtainOpenerArrangement-Final.jpg?raw=1

Terry, East Grinstead, UK

Terry Pinnell
Guest

Fri Aug 17, 2018 10:45 pm

Jasen Betts <jasen_at_xnet.co.nz> wrote:

Quote:
On 2018-08-16, Terry Pinnell <me_at_somewhere.invalid> wrote:
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

XOR gate with delayed feedback on the other input.

Or this thing.

+--------+--- 0V
| |
[R] [R]
| |
+->|-----|-----+--- out
| | |
=== | |
| +->|--+
| |
| ===
in | |
--|>o--+---|>o--+

Yep, thanks Jasen, that's the way I did it:

https://www.dropbox.com/s/na9bro3al1xmek9/CurtainController2.gif?raw=1

That was my last serious electronics project (I became an obsessive
video maker) and I've now forgotten what little I knew in those 14
years! Just glad I made those diagrams...

Wish I'd also made provision for maintenance!

Terry, East Grinstead, UK

Terry Pinnell
Guest

Fri Aug 17, 2018 10:45 pm

Terry Pinnell <me_at_somewhere.invalid> wrote:

Quote:
ZOT <pasmoi_at_pasici.us> wrote:

Le 16/08/2018 16:41, Terry Pinnell a écrit :
The curtain controller I made about 12 years ago toggles the curtains to
open or close on pressing a momentary push button. For holidays I
improvised a circuit based on an LDR inside one of those old mechanical
mains-operated timers. The LDR is flush up against its neon light. That
part of my circuit has recently stopped working and I've started work on
it. But meanwhile I'd welcome suggestions on the *simplest* circuit that
would effectively turn those two long duration LDR states into a short
+12V pulse at each transition. Effectively giving me a parallel
push-button.

It would be a slog to re-install (and probably re-learn) Circuitmaker
right now, so please excuse this rough hand-written substitute.

Terry, East Grinstead, UK

Well done! but how are you moving the curtains, pully, cables? how are
all this arranged?
I am building one but if I can make the motor truning, I don't find how
to go further.

Hi André,

Back in 2004 I explored a bunch of design ideas but here's a rough
outline of the finished thing:

https://www.dropbox.com/s/pyg6eapmctd6pcv/CurtainOpenerArrangement-Final.jpg?raw=1

Terry, East Grinstead, UK

Meant to include this too:

https://www.dropbox.com/s/wiv9tzmjr6hqsd1/20180509-CurtainController-2.mp4?raw=1

Terry, East Grinstead, UK

ehsjr
Guest

Wed Sep 05, 2018 7:45 am

On 8/17/2018 2:05 AM, Terry Pinnell wrote:

<snip>
Quote:

Still trying to isolate the cause of the fault: repeated opening and
closing!

Terry, East Grinstead, UK

Hi Terry,

The problem might be the neon bulb itself. Over time (years)
they can degrade and start to blink. I assume that you can't
see the bulb(s) in normal operation, so the best diagnostic
approach might be just replacing with new.

Ed

Terry Pinnell
Guest

Sun Sep 09, 2018 10:45 am

ehsjr <ehsjr_at_verizon.net> wrote:

Quote:
On 8/17/2018 2:05 AM, Terry Pinnell wrote:

snip

Still trying to isolate the cause of the fault: repeated opening and
closing!

Terry, East Grinstead, UK

Hi Terry,

The problem might be the neon bulb itself. Over time (years)
they can degrade and start to blink. I assume that you can't
see the bulb(s) in normal operation, so the best diagnostic
approach might be just replacing with new.

Ed

Thanks Ed, sorry for delay in responding.

While working on the dismantled timer unit, its ancient gearing
mechanism finally gave up. That settled my growing preference to abandon
it completely as my triggering method. Instead, I've reverted to a
simple LDR, carefully mounted on the exterior side of the curtains, as
input to the Schmitt section of my circuitry. I switch that into circuit
when automatic operation is required, i.e. during holidays.

https://www.dropbox.com/s/yr37n4qsqb9zj58/20180909-LDR-CurtainUnit.jpg?raw=1

The curtains will probably close/open at unrealistic times in the
extremes of winter and summer, although I doubt potential burglars
around here are likely to notice.

Another downside over a set timer is that, from my experience of a
couple of similar devices, is that the LDR's dark/light resistance
gradually changes, requiring replacement or the hassle of adjusting a
preset. Or is there a more robust light-detecting circuit anyone can