How do you design these days?

The ones on the left go to 1K platinum RTDs. The ones on the right are relay contacts to pretend to be a thermostat to our gas furnace. Top are digital and analog interfaces to the Integrity board. All low current, powered by a 12-volt wart and an LM7805 on the upper board.

Not to connect field wiring.

I'm getting a couple tenths of a degree C accuracy from the RTDs. The measurement and math are ratiometric against some 1K 0.1% resistors.

Incidentally, I recommend this gadget

for projects like this. It works as advertised and is easy to use. I expected to have to do some signal averaging on my temperature acquisition, but it's dead stable without. Of course, the braid+foil shielded RG174 runs to the RTDs may have helped.

expander),

out.

I got 100% spares for this project, and a bunch of bare boards for free, so it should last.

Absolutely *everything* about this project worked as expected, first time. Except the software, of course. The hardware I planned and checked. The software, I just sat down and started typing. I had a little trouble shelling out to the FTP stuff while running the realtime part, which I fixed by writing a separate program to do the ftp transfers.

The hard part was pulling the wires.

back to the LM135.

Yeah, I had to consider all sorts of failure modes so that the heat wouldn't stay on full-blast for weeks.

multi-tasking OS either.

The semiconductor sensors usually aren't very accurate. The RTDs are fantastic. I can't imagine how they calibrate them in production.

I considered the Z-wave home automation stuff, but their temp sensors only go down to 40F and are of unknown accuracy. Plus, I wouldn't have long-term maintainability, and remote access could be a problem. And I wouldn't have had a project for this week.

Here it is installed in the ski-boot closet. All I have to do is wire up the furnace control and clean things up.

ftp://jjlarkin.lmi.net/Auto_wired.jpg

Needs more tie-wraps.

John

I tend to manage along the lines of McGregor's 'Theory Y', but not every person responds umm.. 'optimally' to that level of autonomy.

Best regards, Spehro Pefhany

Strongly agree. The only times I deviated from "Theory Y" was when employees or a group could not arrive at a decision by the time it was due. Then I made the decision instead which occasionally p.o.'ed people but it had to be done.

made

how

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amalgamate

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close

You have to debug the real thing anyhow, so it makes sense to try to do the final product first pass. That saves a lot of time and teaches good disciplines. And you may be able to sell it.

John

Cold means nothing to me.

John

I thought you were one of those tropical types who freeze solid at 60 F.

Cheers

Phil Hobbs

Why are pin numbers an issue? You never probe from the backside of a board? The spatial transform is pretty ingrained in me and I spent a decade doing processor design (no PCB stuff).

I use RMA flux. I usually don't clean it. I would need a jet cleaning system to get the flux out.

A past assembly house had problems cleaning our boards which caused all sorts of problems with the water soluable flux they used. Messed up the ~100k impedance areas. They probably didn't maintain their wash solution is my guess.

...and guess where the blame gets fixed and who gets credit for fixing the problem?

I usually put a gouge on the bottom of the package to match the mark on the top, so I can tell where pin 1 is. At that point it's no problem, and I almost never break pins. Dead bugs rule.

Cheers

Phil Hobbs

But are the 'X's worth having as employees? I know the 'X's aren't worth having as employers. Good thing employment is a two-way street.

Oh, a small thing! How many zones? Our current oven is five zones. We're told we should have at least seven and preferably nine for RoHS, where the temperature profile comes dangerously close to the maximum the components can handle. The idea is to soak the board in five or six zones, then spike the temperature in one or two. Balancing the soak and spike gets iffy with only five zones.

Whihc indicates to me (certainly not my area of expertise) that the soak isn't getting it done.

;-)

That is one problem we haven't had. Sounds like your temperature profile is way too high. We did kill aluminum capacitors at one time, but fixed that by getting rid of them.

Not a good feeling.

That's more the size I'd expect. I don't recall what we're using. Again, I'm not an IE.

AIUI, our line came with the building. ;-) We are seriously considering a new oven because of our problems. I'm told that there is all sorts of surplus equipment available out there.

Very deep, too.

That's not John Larkin, it's me. I'm presently waiting for it to get above 60ºF so I can go into the garage and fix a sagging shelf ;-) ...Jim Thompson

Depends what else they bring to the table. It's a pretty strong negative, IMHO. It's hard to be dogmatic about something as complex as a human being. Some just need the right motivation:

Best regards, Spehro Pefhany

On a sunny day (Fri, 01 Jan 2010 01:29:35 +0100) it happened Falk Willberg wrote in :

burn.

ftp://panteltje.com/pub/fireworks_jan_1_2010.avi

I suppose but if you have to babysit, whatever else they can bring to the party would have to be pretty unique.

It's not hard to be dogmatic when the survival of the business is at stake.

Great shot (I trust it's not recent). I love Goldens. The light ones aren't common at all. Seems the breed has been taken over by the red ones.

I had a Golden Retriever when I was 10 ;-) ...Jim Thompson

Until one fine day you have one of those Supertex high voltage chips. Some weirdness happens on the prototype boards, must be a software issue. It's always software. Has to be. Hmm, let's see how that looks on the old breadboard. Grab probe, lemmee see, serial data out was, uhm, umpteenth pin from upper left ... POP ... *PHOOMP*