240v mains to logic output?

I saw the OCP71 mentioned in literature but I don't think I actually possessed one. I didn't get to use many OC series transistors because they were not common on my side of the world even when they were still in production.

By the time I was really into electronics, TO-1 metal cases were more common and I used those by filing off one side. Most of them were also filled with goo, but those goos appeared to be some kind of thermally conductive material to improve heat transfer to the case. I took out most of the goo with something like a matchstick and flushed out the rest with alcohol.

I always thought of (and pronounced) the O as a letter but nevertheless took it to stand for zero-volt heater as it's common practice in conversation to pronounce zero as the letter O when citing numbers.

But yes, I could be wrong about the origin of assigning it to a device number.

I remember the AD162. I thought the AD161/AD162 pnp/npn complementary pair in TO-66 cases was cute, and built a few amps with those.

In Europe it was all letter "O". I still have my old German transistor table from nineteen-sumthin'.

Hey, you can still buy them but at audio-freak prices:

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Joerg,

I vaguely recall an opto-coupler that was close to 1" long, installed over a cut-out gap in the PCB, to meet medical creepage standards (from my ultra-sound days).

I can't find those old drawings. Maybe you know the part? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
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You did ultrasound machines? Which ones?

Nope, sorry. I never used any fancy parts. Right after I started in medical the reps began hounding me, offering fancy iso amps. Burr-Brown et cetera. Every time I told them I'd consider if the price drops well under five bucks, or about 6-7% of what they wanted, plus there is a second source. I've done everything with transformers and gull-wing wide-body optos, under a buck a pop. Even for cardiac you usually only need 8mm creepage but I always shot for >10mm. The CNW wide-body series is nice. Since we always need the paperwork I called, it was HP back then. Less than 10 minutes later it was all coming out the fax machine and we had all the ducks in a row. Ah, the days of good customer service.

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Several chip designs, AND honking switchers, for ADR Ultrasound (when they were here in Tempe, AZ)... ~30-35 years ago :-)

There were some spin-offs here locally, when ADR became a part of some corporation (in Oregon?), but I can't remember their names :-(

Wasn't "fancy" (or particularly expensive), just a long tube (LED on one end, photodiode on the other) as has been described here as desirable.

...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
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I love to cook with wine.     Sometimes I even put it in the food.

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Oh, the ADR-2130? That used to be the VW Beetle of ultrasound, you get sick in the most remote place on earth and there'll be one in the doctor's office. Almost totally in tatters but still hanging on.

ATL, in Bothell, WA. T'is where I started my career.

Last one of that kind I've seen was on some 50's era industrial gear. Or in kids speak, that's "so last week" :-)

Even in the late 70's when I did some work on the side (students always need beer money ...) we used fully integrated stuff. Mostly magnetic though, like two cores inside a plastic package with pins at the bottom. You could transfer almost anything, and cheap. However, analog required to put it on a carrier and digital required NRZ protocols. Usually homebrew with resistive feedback because SN7414 were friggin' expensive and ate power as if it was free.

[...]

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No! You're not comparing like with like! The 0Z4, 0A3, etc., are devices numbered using the AMERICAN system.

The oc44, oc45, oc70, oc71, oc72 are numbered using the EUROPEAN system.

The two systems are different, which is the bit you seem to be having trouble with.

There don't seem to have been European equivalents of the 0Z4, etc., though a picture I've seen suggests that the 0Z4 might have been manufactured by Philips using the American designation.

The fact remains that the letter O in a European number has the same meaning as the zero in an American number.

The difference between the two systems are much more obvious when comparing the 12AX7 with the identical ECC83 ...

Terry

Have you considered alternatives? Faced with the problem of knowing when my furnace is running, I elected to use a microswitch at/inside an air duct to signal when the fan is on.

Maybe Clairex Vactrols? There were Ne input/CdS output gizmos in such cases, actually rather useful for AC work.

Today, I'd use a megohm resistor and a current transformer; there aren't any good long-life options for HV input lamps (the Ne lamps diffuse out the helium and the seal technology has gone downhill since vacuum-tube days).

Can't you just hear it.

Mine is a 6yr old Bryant located in a crawl space it is quiet but I can still hear it anywhere in the house including two stories up in the bedroom.

Its natural gas forced air.Since you mentioned ducts I'm guessing yours is similiar.

paint

To more precisely rephrase... I want the binary state of whether the furnace is running as an electrical input to a monitoring device. Air vane is less complicated than a microphone/amp to "hear" it.

Just the commaned status "heat" or that it's actually working? If just status you could tap off the 24VAC "heat" contact at the thermostat or anywhere off the line that goes to the furnace.

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Sure you can... OR, you can use a microswitch placed at a more convenient vent and do the same thing with much less hassle, no risk of breaking anything in the furnace, no risk of electrical transients blowing up your monitor, no wires running thru walls/floors/ceiling. It's a no-brainer.

For the first prototype of "gross data" I just used the microswitch to interrupt the battery to a clock and log the percentage on-time manually whenever I get around to it.

A switch plus vane only works if you don't have dogs or similar situations. At least no Labradors. We have one from Guide Dogs and it's unbelievable into which spots her hair flies. Once a sliding door wouldn't close. Looked down, ball of shiny Labrador hair.

Or hang a 24VAC relay off of the wall thermostat and place the clock there :-)

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Replying to all here to save multiple mini-posts - hence a bit wordy... Thanks for the suggestions - enjoyed the thread. I admit that my phrasing could have been better e.g "convert 240v mains to a logic output".

The opto isolator solutions mostly take up far to much area when you start adding all the additional components (fuse, resistor, VDR etc) on the mains side all requiring 3mm clearances (and 8mm from the logic side).

The current transformer idea might have worked but the control valves used on my heating system (more below) are only energised during a position change.

My original neon + photo-transistor would have permitted use of bog-standard terminal strips for input and outputs with the components floating on there wires - i.e. no PCB required.

I might explore the photo-darlington suggestion to see if I can get enough tranfer to work direct into the logic inputs.

The 10mS pulses /may/ cause a problem - but since I do not require sharp edges, slugging with a cap may be enough - or the pc program might cope since I am only logging once a minute.

Brief description of the heating system - UK readers can skip :-) ................... It is similar to a Honeywell "S" system. The gas-fired boiler (which is not designed to boil) is switched on by an or-gate of 3 microswitches on 3 separate motorised valves. These valves allow the water to circulate into two heating zones (lower and upper floor) and/or an indirect hot-water cylinder. The valves are controlled by 3 separate time/temperature programmers. All valves are 240v powered. .................

I currently monitor pipe and cylinder temperatures using DS18B20 1-wire devices interfaced to the RS232 port of and old laptop. I was using a single large 240v octal base relay to connected to the water heating demand controller with the contacts to an RS232 status pin to detect when the water heating was required. The plan is to add another two inputs to the remaining status lines.

Thanks for the interest.

--
Geo

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my

only

What's the fuse for? There is already a resistor limiting the current. Protecting the fuse :-)

How about these?

Very small, catches both half-waves, needs only one resistor up front and you are in business.

[...]

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Joerg wibbled on Sunday 31 January 2010 17:11

Speaking as someone who does a spot of electrical installation work and testing, IMO, you *do* want a fuse.

What will be the failure condition of the resistor breaking down or the PCB tracking or some other near short circuit? Bearing in mind the typical loop impedance of the supply at the point in question in the UK could[1] be less than an ohm back to the source and the fuse protecting that circuit (absolute best case that will be a 3A BS1362 and could likely be a 13A fuse if someone accidently replaces with with the wrong size) will have a not insignificant energy let-through before it clears; more than enough to splat the former resistor all over the nearby parts of the circuit, with a risk of causing a mains-ELV bridge and/or damage.

At least a low rated 20mm quickblow should guarantee the PCB remains undamaged and thus easy to repair.

[1] on a good day, but it's comparable with the supply and local wiring impedances measured in my house.

Cheers

Tim

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Tim Watts

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I'm pretty sure Joerg knows that and that he was just joking.---------------> :)