Hi all, first off I'd like to say what a great forum this is! There's obviously a lot of knowledgeable people on here, who hopefully will make my Arduino journey a relatively painless one.
I'm planning a little project to control a gas fired oven, which has three states, off, low and high. What I want is to be able to set a temperature and a time, and let the Arduino control the burner. So my plan is to use a K type thermocouple, coupled to an analogue i/p via an amplifier (AD595), with temp and time settings being programmed via pushbuttons, and an LCD display to give readouts/adjust setpoints. I have the following as my shopping list.
Arduino Duemilanove
K type thermocouple
AD595 Amp
pushbuttons
LCD display (something reasonably simple - 4x20 etc)
2 x relays for the 240v burner control.
Is there anything obvious I've missed, or maybe someone thinks there's a better way to do it?
Sorry if I've posted in the wrong section, this one just seemed to be the most appropriate.
unrelated, but it reminds me of a thermocouple project of mine. The idea was to have a small cage inside a grill, and based on the temperature it would rotate my hamburger for me using a servo. I could never get the cage worked out though.
I don't know how your oven works, but the project looks good to me.
A fire extinguisher isn't a consideration, there's nothing in place to make it feasible. It's an industrial burner, I'm just trying to improve the existing control system (the main priority is the inclusion of a timer for auto shut-off).
I'll look into the diodes, but I was planning on using "off the shelf" arduino compatible relays (such as the ones found on ebay based around an Omron) - I figured it would be easier and plug and play?
I'll get a handful of resistors etc. too - and fuses is a good idea, thanks.
One other thing I'm considering - would I be better to use a RTC for timing purposes, or would it be overkill? The only timing would be for the oven's cure cycle (15 mins), and possibly a cumulative timer for burner on high/low.
Thanks again, I always find someone else will see something that I haven't.
Relays generally contain no diode and need more current than an Arduino can deliver.
I you want it more convenient, you have to pay for it!
When talking of microcontroller compatible relays, I only know of Reed Relays, they optionally(!) come with an integrated diode. Their max current is 1A generally. Omron might be one manufacturer.
Thanks for that. I've had a look around and realised (as you have said) that there's no relay easily available that I could use which can be directly driven from the Arduino, so I'll cobble together a arduino/relay interface. This way I'll know for sure what I've got and I'll learn a bit more about why it does what it does.
On to the shopping list proper and schematics now!
Add parts for a watchdog circuit. Something which cuts the power when the arduino doesn't control the oven any more because of a programming error or something else going wrong.