Heat producing device with Arduino

ladansedesdamnes: Would this be a good alternative to using an H-Bridge, considering only one heating element? https://www.sparkfun.com/products/10636

No.

Well, only if you are actually going to use a 110V or 220V AC supply to a 50W incandescent lamp.

I'm guessing that the box would be fairly slow to heat and cool, so that the heater would need on and off times of many seconds before a response can be observed. If so PWM is overkill and the cheapest option by far for the heater (which would also be safe if you are careful with wiring) is the SSR and an incandescent light bulb.

Make the enclosure or something similar, put a lamp in it of known power, see whether it reaches your target temperature quickly enough. If not, try again with a bigger lamp until you find one that does what you want. Then design your solution around that power requirement.

Out of curiosity, what are you building? An incubator?

Chagrin: Out of curiosity, what are you building? An incubator?

Similar, but simpler. It's actually a box for drying plants and seeds :)

Have been finding lots of Halogen bulbs rate at 12v for the wattage needed (20-40w), but not sure if they work for this :blush:

This kind

Also pretty unsure as how to connect these, is there some kind of socket to plug them in? That would make it easier to replace in case of burnout…

That bulb would work fine, but note - again - two things. You would need a heat shield - a large aluminium plate - between it and the materials you are drying to prevent burning, with air circulated by the fan, and you would need a power MOSFET to control it from your 12V 4A DC supply.

Sockets are readily available. You actually should use PWM, though the situation is a little different with these halogen bulbs. You neither want nor need the bulb to be dimmed to control the heat; you just cycle it on and off over several seconds or even a minute, but you want to limit the inrush current as you turn it on, so you may wish to use a burst (1 second) of PWM to do that.

I had thought about using a surface above/under (depending on placement) the lamp, but was thinking about using some kind of ceramic tile. It would take a lot more time to heat up, but would conserve heat longer (I think - maybe wrongly).

Could I impose on you a bit more to further explain the usage of the MOSFET for controling it, and PWM for driving it?

I know I'm being a bit bothersome to all of you, and I really appreciate all the help, but I have to admit even with my research around the great tips I've been getting I'm finding it a bit hard to understand all of that on my own. I'm more of a programmer than an electronics engineer (lol), so all these concepts still go a bit beyond my knowledge :)

Bump :roll_eyes:

Halogen bulbs work at a very high temperature, which makes them more efficient at generating light but is actually a disadvantage here since it increases the danger of burning something. Ordinary low power incandescent bulbs would probably be safer (and cheaper). You don't have to look for a single bulb which meets your power requirements - there's nothing stopping you from using four or five 11W (tail light / side light) bulbs if that gets you the right power. Sockets for these bulbs are readily available from companies that supply aftermarket parts for people rebuilding/modifying cars, or you can just solder wires to the bulbs.

Try http://bildr.org/2012/03/rfp30n06le-arduino/ for a tutorial on mosfets.

With respect to using PWM to control the lightbulb, something you have to note is that your temperature sensor is only precise to 1C or so. You'll never be able to track the temperature as closely as you would be controlling the bulb.

Chagrin: Try http://bildr.org/2012/03/rfp30n06le-arduino/ for a tutorial on mosfets.

Oooooh awesome, now I get it :D

Chagrin: With respect to using PWM to control the lightbulb, something you have to note is that your temperature sensor is only precise to 1C or so. You'll never be able to track the temperature as closely as you would be controlling the bulb.

That is ok, it doesn't have to be spot on. The LM35's resolution is good enough, but although the error margin could ideally be 0.5º instead of that 1º, I can work with ~1ºC error. Just for future reference, is there a more accurate temperature sensor you'd recommend? The TM36 seems close to the LM35. I found the Maxim ds18s20 but it's a bit more pricey than the LM35. Not too much anyway.

PeterH: You don't have to look for a single bulb which meets your power requirements - there's nothing stopping you from using four or five 11W (tail light / side light) bulbs if that gets you the right power.

You are right, of course. So would I be able to wire them in series, an drive them with just one Mosfet (sacrificing individual control and working with them like it was just one lamp)?

I saw they have the same bildr tutorial with a TIP120 transistor instead of that Mosfet. Only difference I can find is the amperage the TIP120 can take, which is 5A. Considering the lamps will be in the vicinity of 3-4A, could it do the same as the Mosfet? (I'm asking because I can get the TIP120 around here at a local electornics shop, but would have to get the Mosfet from China or something of the kind)

The bulbs should be wired in parallel so if one bulb burns out you don't lose the whole string. Also, if you wired them in series then you would need a high voltage power supply (12V * number of bulbs). Or as another alternative it wouldn't be too bad of an idea to have each bulb or two controlled by a separate output pin.

The TIP120 should also work fine. Mosfets are a bit cooler running / more efficient but I suppose that's not important when you're building a heater.

Once again, thank you very much!
Have learned a new thing once more :slight_smile:

So 1 x TIP120 for each bulb (if 20W) or two (if 10W), controlled by an independent PWM pins. Going to take that approach! :wink:

I’ll take all the advice I got and go about trying to build it.
Once I get something up and running will come back with feedback and state of things (and probably more questions hahaha):smiley: