Anyone ever build an Arduino temperature controller? {GEEKS}

[rksylves]

Yes, I did.

I use temperature probes purchased from Maverick that they use on their ET-73 units. They had no porblem supplying the temperature curves for the probes.

I also use a simple 12v, 10 cfm fan that's probably too big as I've never seen it go over about 50% powered.

The software reads the temperature in the cooker (via the probes) and compares it against the set temperature. It then determines the percentage of the error between the two. It then will turn on the fan via the PWM output by that error percentage. As the error decreases, the fan slows down. That way there's almost no overshoot.

I used a FET to control the fan. The PWM output is connected to the gate. There's a 1K ohm resistor connected between the drain & +12v. There's a 100uF 25v cap between the source and ground. The fan connects across the cap with a connector.

The idea is that the PWM output turns the FET on & off based on the calculated error percentage. When the FET is on, the cap charges and powers the fan. The lower the duty cycle the lower the average voltage for the fan, hence it slows down. The cap will 'average' the PWM pulses to create sort of a variable DC for the fan.

Pretty simple really.

Photobucket seems to be having some issues at the moment. As soon as they fix it, I'll post some photos of it in use and some internals.

Russ

[caliking]

twinsfan: have you seen this thread? http://www.bbq-brethren.com/forum/sh...ad.php?t=77330

Seems like a nifty design, but it does not have a fan, so it differs from yours.

[twinsfan]

My only problem, is, right now, that the fan draws 12 V/0.07 A, (I swear it was advertised as 5 V but whatever), and the Arduino power pins only supply 5 V, which really doesn't move the fan too well.

Can any electricians help me out here? Will the fan not work or do I need to introduce external power from somewhere?

Thanks

[rksylves]

You can translate the +5 volt control voltage to +12 volts by using a transistor, FET, or some other type of switching.

Connect the +5v (suitably limited) to the Base (transistor), or Gate (FET) and put the +12v on the collector (transistor), or drain (FET), again suitably current limited.

Here's a really good place to start. Bob did a good job of explaining how his works.
http://hruska.us/tempmon/

Russ

[stumpzy]

New member here. Is there a more cost effective way to get the Arduino wireless than the Async WiShield ($55)?

I am not familiar with Arduino, but could learn enough to write a decent Web/Android/iPhone app to monitor temps.

Been looking for a new side project since graduation in May :P

Sent from my DROIDX using Tapatalk 2

[twinsfan]

try the xBee line of adapters, I think a completed one is $25 at Makershed.com, the unassembled kit is 10 or 15 bucks

[jamus34]

Originally Posted by NVehr13

This actually crossed my mind the other day on the way home from work. But i wanted to use a Raspberry Pi, Two temps, (one monitors meat temp, one monitors grill temp) and the one that controls the power for the fan.

I didnt see any reason it wouldnt be feasible, may take some doing and may have to write some software for it. but keep us posted, i may get mine underway in the winter when i actually have time to do it

Using a Pi is overkill for a project like this IMHO.

On a side note I'm also interested in a project like this (also on the flip side a wireless refridgerator monitor as I just had to deal with a defrost failure there). I recently picked up a Nerdkit and am working my way through IC's and imbedded electronics (former failed EE student)

I think you can use Arudino's for the controllers and a PI tied to a small LCD for overview.

[HKChad]

I'm currently in the process of building one now, using an Uno and the WiShield. I have 4 Maverick ET-732's for the probes and a 20x4 LCD for display. I have it all breadboard'ed out just working on laying out my prototype shield with my connections. I have an Electric smoker so my controller just runs a 110v SSR to control temps on the oven based around a set point (basic PID). It's a really simple project but will get me much more stable temps. AdaFruit recently ran a tutorial on setting up a Thermistor. The way they did it was much easier than my initial way, which was to calculate the A,B,C values for the 732's and run them through the Steinhart-Hart equation, they also used AREF and +3 volt to stabilize the readings which helped a lot. So I'm in the process of rewiring to take advantage of those changes. Initially I got side tracked trying to use a 'cheap' Wireless solution, eventually gave up on that and just went w/ the WiShield. It works pretty well but the Uno doesn't have much power so my current software is uploading the temps to an EC2 instance then my android app pulls from the EC2, also I have a simple web page on the EC2 that I can use to check on and adj the temps. This way the Uno only has to communicate with 1 external server and any number of clients can attach to the EC2 instance w/o slowing down the Uno. IMHO this is where the CyberQ WiFi screwed up, 3-4 clients connect to it, it almost becomes unresponsive, not very scalable.

twinsfan, you'll probably have to use a relay or transistor as mentioned and power the fan using some other source than the Arduino board. So, if you are going to power Arduino using a 12v transformer just split the output on the transformer run 1/2 the Arduino and the other 1/2 to the transistor/relay then 'pulse' the transistor/relay using the digital out to get the desired fan output like 25%, 50%, 75%, etc something other than full on/off, that's basically what I'm doing w/ the SSR in my project, since the heating element is on/off I turn it on for 10 seconds, turn off for 10 seconds, repeat, that's 50% power, or on for 15 seconds off for 5, that's 75% power, you just have to play w/ the times and get it tuned up for your needs.

If you are interested I have some pictures of the 'in progress' here,
https://picasaweb.google.com/1106977...eat=directlink




-chad

[caliking]

Bump... any more progress?

[twinsfan]

Caliking, I've got the thing circuited out pretty well, but I've decided I'm going to skip on the thermistors and probably just buy real probes. Worth it in the long run.

The other thing is I need to buy some relays to control fan.

The problem is I've been pretty busy and I'm going to have a lot more cash at the end of the month to work on it, just as I have to go back to classes at HS.

I will let you guys know how it works out, I just need to buy more parts at this point.

[Hook_Line_and_Sinker]

Originally Posted by twinsfan

My only problem, is, right now, that the fan draws 12 V/0.07 A, (I swear it was advertised as 5 V but whatever), and the Arduino power pins only supply 5 V, which really doesn't move the fan too well.

Can any electricians help me out here? Will the fan not work or do I need to introduce external power from somewhere?

Thanks

Your fan is clearly marked 12 v buy a different fan they are cheap

[HKChad]

Well mines done, just tweaking the Software.





I used Maverick ET732 probes with a 22k resistor.

[cameraman]

Originally Posted by rabeb25

I did but it resides in my brewing system ;)

That is wicked.

[caliking]

Originally Posted by HKChad

Well mines done, just tweaking the Software.



I used Maverick ET732 probes with a 22k resistor.

Were you able to use the Arduino shield for wifi? I read some time ago on the tvwb thread that it no longer worked for this application since a different version is being made and sold now.

twinsfan: keep us posted!

[HKChad]

Originally Posted by caliking

Were you able to use the Arduino shield for wifi? I read some time ago on the tvwb thread that it no longer worked for this application since a different version is being made and sold now.

twinsfan: keep us posted!

I used the WiShield 2.0. They are no longer making them but you can still get them on eBay. Little expensive but a pretty decent API. I tried using a WizFiShield that simulated Serial but there was no api so programming in it was a bit of a PITA, setting it up was all AT commands, so I dumpped it and went w/ the WiShield even though it's no longer supported.

Chad