Outdoor delay switch

[PCPaul]

Because pneumatic or mechanical delay switches with outdoor fitting kits
are extortionately expensive, I was wondering if anyone had a good
circuit for making my own...

Ideally a single button press should start a delay timer that activates a
light for a few minutes (to light the way from the garage to the house).

I'm happy enough with digital electronics but my analogue is weak.. it
seems like there should be a way to use mains only for this, with a triac
or SCR to switch the load (<1000W) and maybe some sort of rectified feed
to a CR circuit to do the timing. But I'm sure there must be a better
way...

The issue of it being outdoors (basically replacing a dead pneumatic
supposed-to-be-weatherproof switch) is also a problem, but making a
sealed rainproof box with a suitably rated momentary switch shouldn't be
too difficult.

Any ideas?

(I've seen motorised timers in an earlier thread but they were 110V
and in the US - I'm in the UK on 240V 50Hz).

 

[PCPaul]

Seems to me, PCPaul, you are basically wanting a motion sensor light
fitting with two movement sensors (one at the front door, one at the
garage door) and, maybe, multiply light fittings.

Is there nothing on the Commercial market that meets your needs?? (Why
re-invent the wheel...?)

Well, there are a few reasons...

- The garage and house are a long way apart and on a different phase of
the mains, so running a wire between them would be difficult and
expensive.

- At the garage end the motion sensor would have to pick you up as you
went through a narrow alley (from either end) - so conventional PIRs that
detect you as you move across the beam aren't very good for that
application - I tried one there. To pick you up from either end would
need either two sensors or a true 180 degree sensor, which gets tricky,
and again puts the price up. There isn't enough height to mount the
sensor high but looking straight down, to scan both ends at once.

- commercial switches apart from the mass market '500W xenon floodlight
with PIR' are a silly price. Commercial weatherproof delay switches are
absolutely ridiculous.

- (and finally a major reason), it seems like a nice project to do to
start getting into mains/analogue circuitry...

 

[JeffM]

Because pneumatic or mechanical delay switches
with outdoor fitting kits are extortionately expensive,

Given any thought to how you will make *yours* weatherproof?
Priced an appropriate enclosure and fittings?
Ever built anything along these lines
(low-voltage control / mains on the output)?

Ideally a single button press should start a delay timer
that activates a light

A solid-state relay seems like the easy way for a 1-time project.
Logic-level inputs and whatever-you-specify on the output.
A parametric search at your favorite parts vendor's site
should turn up a likely candidate.

for a few minutes
(to light the way from the garage to the house).

This is the way most folks get a delay of over a minute:
http://www.google.com/search?q=CD4060+Divider-and-Oscillator+datasheet

 

[PCPaul]

Given any thought to how you will make *yours* weatherproof? Priced an
appropriate enclosure and fittings?

I have an IP56 momentary switch already.. but I need the delay trigger
and mains switching to go on the back of it.

Ever built anything along these
lines (low-voltage control / mains on the output)?

Yup, although quite a while ago. I did an Electronics Engineering
apprenticeship but after doing the basics took a very strong digital
route - so the analogue got a bit left behind. I'm also intimately
familiar with the UK Wiring Regs and have rewired whole houses, so mains
isn't too scary. It's the bit in the middle that I don't have at the tip
of my tongue.

If it *was* low voltage control, mains out I'd be OK. It's trying to do
it all just from mains without having to put a 5V DC supply in there that
I'm really after - hence trying to do it all with AC and high voltages.

A solid-state relay seems like the easy way for a 1-time project.
Logic-level inputs and whatever-you-specify on the output. A parametric
search at your favorite parts vendor's site should turn up a likely
candidate.

Like I said, can it be done without logic voltages? I vaguely recall a
single chip mains->CMOS levels regulator, but I was hoping to avoid even
that if possible. Is there no way to do it simply with AC-only
components? It seems like a simple enough task, basically a monostable
but working with mains voltage AC. And preferably solid state. I'm not
even that bothered about the precision. +/-20% is no problem at all.

This is the way most folks get a delay of over a minute:
http://www.google.com/search?q=CD4060+Divider-and-Oscillator+datasheet

Cheers, I've used them. On the digital side I've done everything up to
and including designing a 6502 based controller with paged memory and a
homebrew touchpad. It's purely the AC electronics (rather than electrics)
side that I wanted to pick up more about... without studying it in depth!

I know I could buy PIRs off the shelf, or get an electronic or pneumatic
delay switch, but I fancy doing it as a small project instead.

 

[Baron]

- commercial switches apart from the mass market '500W xenon
floodlight with PIR' are a silly price. Commercial weatherproof delay
switches are absolutely ridiculous.

£10 in Focus !

- (and finally a major reason), it seems like a nice project to do to
start getting into mains/analogue circuitry...

A good enough reason.

 

[PCPaul]

£10 in Focus !

For a PIR floodlight, yes. But for a weatherproof delay switch? You must
be looking at different shelves to me - more like £25 for a pneumatic
switch and another £20 for the outdoor kit for it...

A good enough reason.

I thought you'd understand ;-)

 

[PCPaul]

browse.jsp;jsessionid=PYIT2ONBRZU42CXDUZ1G3PQ?N=500003+1001309+148378
+182171&Ntk=gensearch_001&Ntt=mallory&Ntx=&_requestid=209120

---
Oops...
That didn't come out right.

Go to the Digi-Key website then find aluminum electrolytic capacitors
and narrow the search down to 2000 to 2400µF and 360 to 450V.

That circuit is more like it.. the random phase trigger simplifies things
somewhat. Wonder if I can just sample it ;-)

I guess the cap needs to be that big to keep the optocoupler LED lit for
100s or so..

Since I don't really need the isolation, is there a way to do it that
uses a scaled down RC circuit to switch a transistor based trigger
instead? I'd guess you could do that with a few uA instead of the 60mA
the optocoupler needs.

 

[PCPaul]

---
Yeah, there is.

I thought about it after I posted the other circuit, but didn't get
around to updating it.

I'll get on it sometime today...

Thanks John

That's pretty good really, but if it can be brought down so the cap is a
convenient size (and price!) and will fit in the shallowish backbox of
the switch, that would be a great improvement.

 

[PCPaul]

---
Fixed at:


JF

lol - one of those days, eh? I've had *lots* of those...

So the post at the link is correct?

Or do you want to email it direct, my address works.


Thanks for taking the time to get this far!

Paul

 

[PCPaul]

I can see the post at abse, but the pdf comes out as bits of pdf text.
Please could you send it straight to me, saves all the uuencode/yenc type
hassles..

I'll send it straight back if it's your only copy ;-)

An interesting thought when designing anything new.. just because this
design works perfectly *electronically*, could it be improved along other
axes?

I do recall making a car lights-on alarm buzzer with a delayed off using
a 555, a couple of caps and resistors and a speaker. It didn't look
anything like any of the millions of sample 555 circuits I'd seen, I was
just fiddling about with some breadboard and there it was.

I tended to muck about with analogue stuff back then but didn't get on
with the theory so much - I think computers were just so much more
appealing..

I did like the little tricks I picked up like putting a resistor in
parallel with a linear pot to approximate a log pot response - I needed a
small pot to go in the amplifier we had to design as an apprentice
project and 'stores' only had huge fugly log pots and nice neat linear
ones..

Just make sure the box is waterPROOF and there's no way the circuit can
be touched accidentally when it's energized, since there's no galvanic
isolation from the mains.

Should be OK, it's a commercial IP56 rated switch in a box. Not sure if
you do IPxx ratings on that side of the pond - that translates to:

5x - protected against enough dust getting in to affect operation
x6 - protected against direct jets of water and heavy seas(!)

The next ratings up are 'dust tight' and 'sealed against immersion up to
1m deep' so IP56=a pretty well sealed box.

I will still be careful though, I've had a mains belt before and I
wouldn't wish it on anybody. With 240V you don't go touching stuff with
the back of your hand to see if it's live...