Depending on where you live of course but that is not much more than room temperature so this should be doable with a fairly modest heater.
You will still need a closed insulated container. That plastic container you described might have good electrical insulation but thermally the insulation would be pretty much non existent. The container would also have to be closed or all the hot air will just go out the top.
Have you thought about a small bar fridge or a medium sized Esky. Even a small well insulated oven might do. Better if you could modify it to control the temperature more closely.
Once you have the insulation sorted you might get away with several of these mats in the bottom. But there is a trade off of course.
Say you have 4 in parallel @ 5V. That would give you 12W BUT the current would go to 4 X 0.6 = 2.4A. So the current is going up to provide that extra power. What if we connected in series? OK we are now back to 0.6A to get 12W But the required voltage has now risen to 20V.
As the story goes you get nothing for nothing. Watts is Watts is Watts and there is no getting around this. If you require X Watts to do a job that is what you are going to have to supply from somewhere. The formula is simple… Volts multiplies by current (Amperes) equals Watts.
For this application you might need some Watts up your sleeve as it is one thing to heat a container full of air but when you put a mass of your 1.5kg of dough in the temperature inside the container will drop pretty substantially and you will need a bit extra for reasonably quick recovery.
I think you would do well and re visit your requirements. With good insulation you might only need a mediocre heating system but with poor or no insulation you are going to lose the battle. We are talking thermal insulation here, not electrical.
Cheers Bob
Hi again Dion
Regarding that toaster oven element. If that started life as a 240VAC element and you want to experiment you could increase the 12V to see if you could get enough Watts to do your job without any damage. Might be worth a thought.
Cheers Bob
By my maths powering a 46.5ohm element with 12V still gets me back to ~3W?
I could use a laptop power source which is 20V 2.5A? I would then need a voltage regulator from 20V down to 9-12V to make it suitable for the Arduino VIN?
I am considering ditching the low power route and just use the toaster oven element with 240V mains power and a potentiometer to moderate the element output down to something more suitable for low temp heating.
I will also come up with an insulated box to safely house the element.
That is correct but I meant to increase the voltage above 12V.
There is NO low power route. As I said previously Watts is Watts is Watts and that is what is going to provide the heat. Low voltage higher current or high voltage lower current. All amounts to pretty buch the same thing.
NO, very dangerous. The potentiometer could flash over and explode unless it has been designed for the job. Reducing mains power usually involves some phase switching, leading or lagging. Like a fan speed or light dimmer control. A potentiometer is usually used to control other switching methods.
If you want to try the toaster element you could use a “Variac” to get into the right ball park. But be careful, a Variac is an Auto Transformer and does not isolate the mains. But you can usually adjust the output voltage from above 240 to quite a low value smoothly. I could not find a Variac on Core site but if you want to have a look at what one looks like Jaycar stock one Cat no MP3080. I actually have one of these.
Cheers Bob
Hi Dion
Yes, that certainly will do the job. It was a bit confusing as this device is not a “potentiometer”
It is a large light dimmer or fan speed controller which works a bit differently. This works by “cutting off” a part of the sine wave progressively allowing the remainder through. This progressively reduces the RMS or Heating power value which is what you are interested in. The resultant wave form is like the original sine wave with bits chopped out of the leading or trailing slope so varying the RMS (heating power) value which suits your application.
The Variac on the other hand is a “variable” transformer which will retain the sine wave shape. But like the Variac I don’t think this device will isolate the 240V mains so take the same care.
This device is suited to heater elements, light dimming, fan speed etc where the shape of the sine wave does not really matter but should not be used for applications where the sine wave is important
Cheers Bob
