The nano is only $40. less than Bluetooth modules for arduino boards. Can I communicate with my device over this bluetooth connection, or is it dedicated to just uploading code?

My goal would be to be able to write an Android app that could provide a display/control for my arduino devices, instead of getting into LCD drivers.

Arduino nano clones can be had for $16.90(includes shipping)

http://www.dealextreme.com/p/arduino-nano-v3-0-81877

BT module $9.20 (includes S&H)

http://www.dealextreme.com/p/jy-mcu-arduino-bluetooth-wireless-serial-port-module-104299

As for the probe, your going to probably want a food grade one, Looks like they have come down in price, I recall clsoe to 1/2 the cost of Mikey Sklar's YATC2 was in the probe.. looks like they are down $8-20 range

http://www.amazon.com/Replacement-Probe-TW362B-Oven-Thermometer/dp/B0048GD8RY/ref=pd_sim_sbs_k_2

Probe rated to 392 F
Cable rated to 500 F short term (probably extendible by insulating/heatspreading.)

Quote from adric on January 4, 2012, 16:38
Arduino nano clones can be had for $16.90(includes shipping)

http://www.dealextreme.com/p/arduino-nano-v3-0-81877

BT module $9.20 (includes S&H)

http://www.dealextreme.com/p/jy-mcu-arduino-bluetooth-wireless-serial-port-module-104299

I dunno how the programming will be for the BT module.
It looks like a great way to go, though.
Since that one has wired USB, I'm sure I could use that BT module for the human interface.

I thought that the new, fancy MAKE nano used a BT only (no USB) interface. $40. Serial over BT protocall.
Either should work.
I bet that if we can communicate over the "serial" link to the Arduino, that would be easier than using libraries to speak over the BT add-on module.

http://www.amazon.com/Replacement-Probe-TW362B-Oven-Thermometer/dp/B0048GD8RY/ref=pd_sim_sbs_k_2

Probe rated to 392 F
Cable rated to 500 F short term (probably extendible by insulating/heatspreading.)

I bet this will work fine. Especially if I only have the tip inside the cooker. In fact, upon second look that seems to be EXACTLY the probe on my meat thermometer... I gotta go and see if I can increase my order to several of those probes.

Quote from Mr.What on January 5, 2012, 09:16
I don't think I need food grade... just for oven temp, not meat temp. The problem I'm seeing with thermocouples is that they react to temperature difference. I think most of them are only a few inches long. I wonder if my digital meat thermometer somehow has the refrence temperature at the digital device, some 3-4' from the probe? That probe looks a lot like my meat thermometer, and it could work just fine for this app. I might not need to put the cable in the smoker... just drill a hole for the probe tip?

Food grade may not be needed, but its nice to know its stainless and non fuming, and designed for this kind of work. its probably nearly the same as your thermometer. they are very commonplace tech, although the cost is mostly in the Q&A that you reliably get the same signal at the same temp every time, and that the reading range is pretty flat.

Will I need some sort of pre-amp (op-amp signal conditioner?) to read the thermocouple from an Arduino A/D... or can the Arduino be set up to read the thermocouple voltage directly?

Not sure, but i think it can via the analog inputs just read it, with a known source one can calibrate it.

Other question to repeat... can I communicate with my "sketch" over the USB, or is the USB dedicated for program upload? On VxWorks, we can give a "load" command over serial, then after our image is loaded, it returns to a command prompt, over which we can even do things like printf and scanf.

Yep you can get serial data back over the usb from the arduino, (i was mentioning tethering it for datalogging/offboard control)

In the spirit of iterative development, I'm thinking of designing a circuit to run uncalibrated. Just turn a dial for warmer/cooler... let the human deal with figuring out what pot position corresponds to 200F for a given cooker on a given day. (Since thermocouples respond to temperature difference, my "reference" voltage changes weather it is 20F outside (winter) or 110F outside (summer))

I think that's why they use thermisters in most probes/thermometers because at 100C you get X resistance and at 50c you get 1/2X (or whatever their profile is), once you have the program setup and the type of probe zeroed in, i think you could have it pretty accurate. now i dont know if outside temp changes inside temp enough to change the cooking profile/times.

That's why i was thinking we should stay clear of Thermocuples. And stick with the simplicity of a thermistor. some of the Silicone/Germanium Thermistors can deal with -40C to 500C http://www.adsem.com/gpage1.html and it looks like they are frequently used in ovens and alarms, and other sensory stuff. and they have predictable output based upon resistance at a given temp.

And they have the advantage of just needing a simple resistor to serve as a voltage divider for arduino. here is sample code and a simple schematic. for a normal non high temp thermistor (so some code changes will probably be needed) http://arduino.cc/playground/ComponentLib/Thermistor

id say find some hi-temp insulated wire. (ive seen it for the internal wiring of heaters and other appliances) this site atleast outlines some of the types and their capable range http://www.omega.com/techref/wireinsulation.html

looks like this kiln supply place may have the wire we would need if we cant find it in a local hardware/electronics store. http://pottery-kilns.com/magento/kiln-parts/wr-12-hi-temp-insulated-wire.html

and then id use metal crimp connectors. and depending on the conditions(i really dont know how corrosive it is where you might be wanting to read temperature from. perhaps crimping it into a small piece of pipe or perhaps folding a small envelope of thin sheet metal

Do you have a convenient way to attach a project "shield" to an arduino development board? Perhaps even just some rows of pins I can plug into the arduino board sockets, onto which I can solder my LED's, sensors, and servo drivers. Where can we get some old-fashioned, no-connections pegboards to wire up our support circuits?

On another note... I have not yet been able to implement 2-way communications with the Arduino over serial. Perhaps the serial monitor is problematic. Here are some tips to try from the WWW:

if you did Serial.begin(115200), and your Arduino is at ttyUSB0, do something like

stty -F /dev/ttyUSB0 cs8 115200 ignbrk -brkint -icrnl -imaxbel -opost -onlcr -isig -icanon -iexten -echo -echoe -echok -echoctl -echoke noflsh -ixon -crtscts

Then you should be able to do things like :

tail -f /dev/ttyUSB0
echo set temp 220 > /dev/ttyUSB0

to communicate. I hope that we can do both simultaneously. I dunno if a similar device will exist to use via Java on Android.

Another method suggested was

screen /dev/cu.usbserial 9600

You may need an stty command similar to above to get the settings on ttyUSB0 as desired.

There is also

cu -l /dev/ttyACM0 -s 115200

Found the problem with my software. Arduino Uno has 2K ram limit. Although my code was small, I had 1700 byte array of history, that I was planning to analyse for adaptive control parameter updates. That took my total program over 2K RAM. I will simplify my AVR code, and do any adaptive control from the host, monitoring data over the serial port.

DealExtreme no longer seems to list the $8 Arduino bluetooth module. However, they have a generic BlueTooth serial transceiver for like $6. I hope it is the same thing, without the headers.

My best hopes, so far, are that all I need to do is hook up 4 wires: Gnd, Vcc, TX, RX to the proper pins on an Arduino, and I now have serial over Bluetooth. No extra libraries or anything. I'm hoping that it will take over for the USB hardware/programming serial when the USB is not plugged in.

On the other side, I see several bluetooth-serial terminal emulators for the Android. My hope is that I can just use one of these and be able to use the same simple serial communications interface I have been using through USB to control (if not program) the Arduino device.

Could it be this simple?

i.e. If I design a serial interface, I type commands, and the Arduino prints out status, I can do this from a "BlueTooth serial terminal" app, and have a wireless interface for my device, without changing any Arduino software, or writing some sort of bluetooth client?

Thermistors are cheap, but non-linear. The math is not bad, just slow.

Pro-level high-temp sensors include RTD's, not sure of the cost (I didn't care when I did a system with RTD's.) Thermocouples are also possible. Both will need conditioning. I have a circuit kicking around at home, but the interwebs is faster.

One thing to be aware of: don't get so hot you melt the solder!!! You will need high-temp wire and a high-temp epoxy or other potting material. (Careful - the expansion/contraction of the potting material vs the wires/leads/etc can cause a cracking failure.)

A quick Digikey search for thermistors to 250 degC shows 7, over a variety of resistance ranges and tolerances (1% to 5%). First one is 495-2625-ND. All are under $4 for quantity 1. Another is 235-1104-ND, datasheet at http://www.thermometrics.com/assets/images/dk.pdf

One of the inaccuracy points is the resolution of the ADC over the temperature range.

The link Adric has above is a good start.

When I say "disconnect serial", I mean thinks like kill the screen process. It is just a software/device file disconnect. not a physical one.

These are AT commands to control this bluetooth module
http://quelab.net/wordpress/wp-content/uploads/2012/02/BT0417C_ATcommand.pdf

Linkdump,

Here is a nice article on using mosfets for controlling larger power things than the arduino can control, Mr What, has already covered alot of this in his smoker project, but this one is pretty nice and clear for should be handy for anyone new to these things

http://bildr.org/2012/03/rfp30n06le-arduino/

When using a Bluetooth/SPP module wired to the standard serial TX/RX pins, D0 and D1, it conflicts with serial control from USB. Is there a way that I can detect when the USB cable is present, and disable the Bluetooth module?
Electrical, software, or mechanical solutions all OK.

The best electrical solution I have is a SPST switch on the module power line. I checked this, and it does work. It would be convenient if I could get this to happen automatically when the USB cable is plugged in.