Motion detector

Sylvia Else Inscribed thus:

I've had relay contacts feeding a light bulb weld together when the bulb blew and the relay still switched the other pair of contacts just fine.

--
Best Regards:
                     Baron.

**That was my original suggestion. TRIACs are cheaper than relays. I've seen systems where a very small relay is used (for isolation) to drive the gate of a TRIAC. It is possible that such a system is used in the OP's one. More likely it will be the suppression cap.

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Trevor Wilson
www.rageaudio.com.au

Bizzare. Optoisolators are trivial to use for isolating triacs and can have a photo trigger diac to eliminate everything on the load side but the triac. I guess if it is a choice between a 10 cent optoisolator that'll last forever, and an 8 cent relay that'll crap out in a year, they take the latter choice.

There is a test switch, nobody touched it. It's been working fine for years.

YOu don't need to do that. If it's on a switch you just shut the switch off and on real fast and it toggles it to stay on all the time. To go back to motion detecting shut the switch off for 10 seconds or until you hear the relay release then turn it back on.

Yea. welded by ice.

Well, now, perhaps. But we don't know how old the faulty device is.

One advantage of a relay is that it really does cut the load current to zero, near as makes no difference. I haven't seen a solidstate device that does that, and at 240V, even a few milliamps adds up to a watt or so, and is running 24/7.

Sylvia.

"Stupidest Bitch Alive Sylvia Else"

** A triac cuts off load current as near as make no difference.

Leakage is in the uA range - not mA.

You IMBECILE !!

..... Phil

**Complete bollocks. A TRIAC has miniscule leakage. Less leakage current, in fact, than the suppression capacitor across the relay contacts. MUCH less.

--
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson"

" Stupidest Bitch on Earth Sylvia Else"

** The leakage current flowing in such a suppression cap produces no heat and consumes no power.

Cos the PF is zero.

..... Phil

In the overview of triac-based solid state relays that I find at Omega.com (they make these), they write:

The output-circuit ratings of the more common isolated SSR's, most of which are designed to control ac load circuits, are very similar to those described above, except that OFF-state leakage is usually higher---on the order of 5 mA at 140 V for a 5-ampere device---still only about one-thousandth of the load current rating. The data sheet for the AQ-R 10-to-40-ampere solid state relays specifies a maximum off-state leakage current of 2.5 mA at 100 volts AC, and 5 mA at 200 volts AC.

In the STMicroelectronics data sheet for the T835H and T850H "high temperature 8A Triacs", they cite a maximum leakage of 5 uA at a junction temperature of 25 degrees C, and as much as 3.1 mA at a junction temperature of 150 degrees C.

Teccor's Lxx08xx series seem to go from the 10-50 uA range (25 C) up to as much as 3 mA (100 C).

It looks as if there's a fair bit of range in the specifications and behaviors, depending on temperature, voltage, and on whether you're talking about just a triac in isolation or about a whole solid-state relay circuit.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
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**Indeed it is, unless it the relay contacts happens to be in series with a resistive load (like an incadescent lamp).

--
Trevor Wilson
www.rageaudio.com.au

**We can be absolutely certain that a motion detector light switch (unless it is in a top secret, government funded military situation) will not be using a SSR.

--
Trevor Wilson
www.rageaudio.com.au

"Dave Platt is an IDIOT "

** SSRs are not just triacs.

There may well be a snubber cap inside that draws AC current but causes no dissipation.

IDIOT !!

** QED

** If the device is off - guess what the temp is ???

IDIOT !!!

** QED.

** If the device is off - guess what the temp is ???

Pal - when next you have nothing to say -

SHUT THE FUCK UP !!

You pathetic, radio ham IDIOT

.... Phil

...

and I think you can be pretty sure it won't switch 40A, although you never know when you might want to have 2400watts of lighting.

"Trevor Wilson" > "Phil Allison"

** Huh ????

Cold lamps have typical resistances under 100ohms

The AC current from a 47nF cap at 240 volts is 3.5 mA

Do the math.

I get a PF of 0.0014

Over to you.....

.... Phil

**Misunderstanding and poor wording by me. I do not dispute the PF. I was making the point that the current through a typical suppression cap exceeds the leakage current through a typical TRIAC. It was for Sylvia's benefit, since you already knew that.

--
Trevor Wilson
www.rageaudio.com.au

**No problems over here. A small (TO-220), heat sunk TRIAC will easily switch 2.4kVA of resistive or, (more importantly) inductive loads. 2.4KW lighting tends to be very inductive. Relays die very quickly under such loads.

--
Trevor Wilson
www.rageaudio.com.au

It didn't, and doesn't, seem relevant though, given that my point related to power consumption.

Sylvia.

**It is very relevant. The leakage current through a typical suppression cap across a relay is in the order of milliamps. The leakage across a tyical TRIAC is in the order of microamps. The use of a relay in such an application does not guarantee zero power consumption when non-operational.

--
Trevor Wilson
www.rageaudio.com.au