Really dumb newbie questions

patches

Sorry for the stupid newbie questions… I’ve tried to figure these on my own out but haven’t been successful.

I’m building a temperature controlled door opener as my first project. I have a sunroom that gets quite hot in the winter for a few hours while I’m at work. My project will open an interior door from the sunroom to my house when the sunroom is hotter than the house, then close it again when the sunroom cools down in the late afternoon. Pretty fun, and I think I can knock 25% off my heating bill (got to love a project that pays for itself in a year!).

I’m prototyping with a BOE, but intend to build the final project on a super carrier board. My questions are mostly mechanical. I’ve never worked with electronics before, so I’m unfamiliar with the physical properties of the devices.

Question 1: What is the pitch spacing on the prototyping area of the board? Is it 2.5mm or 0.100” (2.54 mm)?

Question 2: I need to connect two temp sensors to the board. I’d like to make them detachable. They will each be three wires. Parallax sells a “3 pin single row header (long)” on their store under Components > Wire/Connections, but it looks like its for a breadboard, not solder-in. What is a good solder-on connector system? Digikey has 200+ pages of connectors, it was a little overwhelming.

Question 3: For temp sensing, I’m using LM34 sensors connected as described in the 7th post on this page by Tracy Allen (works like a champ – the logic is relative so I don’t need to know actual temp values, just relative ones). Ideally the leads to one of the sensors would be 20 feet long. Is this realistic or the resistance too high? Also what size wire would be used for this?

Question 4: When you finish a project, where do you buy a case/box to mount it in?

Sorry for the dumb questions.

Mike Green

1) It's 0.1"

2) The long headers will work and solder nicely. There's just a longer tail to clip off after soldering. You can buy strips of headers from any of the suppliers like Digikey or Jameco or Mouser. You want the 0.1" ones. Try Jameco first. Their catalog is less daunting and you can always find the same manufacturer and part #.

3) You probably want either shielded or twisted pair wiring to reduce the likelihood of noise being picked up by the longish wire run. 24 Gauge or something in that neighborhood should be fine.

4) The major electronics distributors have plastic and metal cases for sale. SparkFun Electronics has a few cases that might fit a BOE or Super Carrier Board. I've used small wooden file boxes sometimes. They're easy to drill and file. You can sometimes find them at "big box" stores like Wal-Mart or Super Target or Costco.

patches

Thank you very much Mike, sorry again for the dumb questions.

Lab Rat

a note to the 200 pages
i get the mouser catalog quarterly and it just gets bigger and bigger with each issue somewhere in the world of 3 inches thick plus i get digikey allied and jameco
now that is overwhelming but i like it it provides an individual with the best buy after figuring out where to stash 30 pounds of catalogs
good luck with the project

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Parallax posesses power beyond belief.

Believe in it.

SRLM

I just use the catalogs to "pimp" my room, not to actually open. Why spend half an hour looking in the paper when all the online versions (except digikey) make it so easy to find stuff?

As for #4, I've used styrene, which works pretty well. Custom built plastic cases with minimal effort.

Post Edited (SRLM) : 11/19/2008 6:22:31 PM GMT

Carl Hayes

I assume you're doing this for the learning and the fun, because otherwise there are much better ways to do this than using the better part of $100 worth of stuff to do the job of two thermistors and a comparator, at about $4.00 total if you buy them at the Neiman Marcus of electronics emporia. Some things just don't need a computer, however tiny.

On the other hand, your project sounds like one well chosen for the learning experience and for the fun. I would go to Radio Shark and get a couple of their little solder breadboards (basically a PC board with a matrix of holes) to build it on. The temp sensors you plan to use will be low-impedance devices, so noise shouldn't be much of a problem if you just use twisted pairs. I'd use telephone wire, also conveniently available at Radio Shark. Bah, that's juvenile, isn't it? Conveniently available at Radio Shack. Telephone wire has several twisted pairs in it, conveniently all different colors so you can tell which is which at both ends.

But aren't you afraid of admitting the casual daytime burglar?

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· -- Carl, nn5i

Chris Savage

Patches,

In the future please try to use a descriptive subject line. The one you currently have doesn’t indicate what you need help with.

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Chris Savage
Parallax Engineering

Tech-Man

You should try futurlec.com for all the parts you need. Also a cheap way to get headers is find an old computer mother board or floppy drive. They have a bunch inside.

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There are no Undo buttons in life.

patches

Thanks everyone.

Carl, I started this project with a microcontroller instead of a comparator because... I didn't know what a comparator was, or that such a device existed! Once I get it all working I may try to redo the circuit with a comparator instead of a microcontroller. Learning the microcontroller is good though - there are a bunch of projects I would like to do once this one is sorted out. As for burglars, the door is an internal door, the house remains locked up tight throughout.

So far its coming along nicely... though its pretty ugly, not nice and tidy as I had hoped.

Carl Hayes

So far, by the way, your questions may be newbie ones, but to me they seem intelligent and thoughtful. When do we get to the "really dumb" ones?

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· -- Carl, nn5i