Finally: network enabled fermenter temperature controller

[admin]

Finally found one...

http://arduino.cc/forum/index.php?topic=114436.0

I have ordered an Arduino Nano, dual relay board and ethernet module, all for less than €20. I have a DS1820.

Unlike the lad above I plan to solder everything to veroboard as the Nano is ideal for that, as are the other components, and it will give it good structural rigidity.

I'm also using regular relays that cost a quarter the price of the 25A SSRs, which are overkill anyway.

Version 1.5 might be able to run a preprogammed schedule.

Version 2 might have a display and be settable onsite.

[rukkus]

A rasp-pi paired with an arduino can be really handy as you can code using higher level languages on a full linux platform and just talk using a serial interface to the arduino. You can add usb wifi etc very easily this way. Plus you get access to graph plugins or whatever library you want.

[Stitch]

The SSR's would allow for PID control. Relays will only give on/ff control. Relays have a finite number of times they switch. You plan on only on/off control??

[rukkus]

I've heard of power related problems sometimes alright, i havent had mine running over a long period of time yet.

I was very impressed at how quickly you can knock out stuff with the two combined though.

[Stitch]

It's a fridge on the cooling side and a bulb on the heating side, so SSRs wouldn't be of any benefit?

Ah fair point once door is closed then you won't have much loss. Thought you might be trying to control kettle elements.

[JD]

Given that the relays will be switching main voltage I would strongly recommend against using Veroboard for the relays. I'd mechanically mount the relays on a panel and wire the AC directly to and from them. The rest of the circuit is all low voltage so Veroboard is fine.

In college, many years ago, a class mate designed and build a light weight mains isolator. He used Veroboard for the whole circuit. The initial test was such that we ended up declaring his circuit as an example of the famed  "Bulk emitting substrate" class of devices. Basically it became a Veroboard doughnut in about 3 milliseconds and he ended up looking like a cartoon: two white eyeballs in the middle of a black face.

Shame to see history repeating itself.

/J

[JD]

There are no issues with using such a board on standoffs. Keep an eye on clearances underneath is the only proviso.

They're 10A rated contacts so you should have no issues with a fridge and bulb. You will likely get about 1,000,000 make/breaks before failure so given the application you're likely looking at fridge failure before relay failure.

/J

[Ciderhead]

Ciderhead is regretting now choosing woodwork over Electronics when he was 14.

[JimmyM]

Think i've a few ds1820s spare.
I'll have to find them though!

[Ciderhead]

So that I can keep the box that contains the goodies as small as possible I've decided to go with trailing sockets. Local electrical wholesaler doesn't have them, so from ebay I ordered 4 of these. £1.49 each, free postage to Parcel Motel.

Want to get a project box with a transparent lid so that I can see the good stuff.

With your wiring make sure its Flame retardant, glass would be good 
You can buy them with Polycarbonate Smokey transparent fronts, Transparent Plastics and Full Flame retardation are not great bed buddies

[JimmyM]

So the ds1820s i gave ya worked?

[JimmyM]

What are they? AND gates or something? Too lazy to google
Id say i do...

[JimmyM]

Jesus im good - wtf do you need AND gates for?? you have a micro processor sitting there.

...Ive loads of that sort of shit.

[JimmyM]

Ah very clever
I'll make sure I have them - nearly sure i do.

Arduino - well the atmel chip - can do 3.3v as well. There may be other components on the board that dont do 3.3v though.

[JimmyM]

Haha cool!
Prob used up all the memory with the image