Hi folks
The Arduino's been in the drawer for about six months but now I'm getting itchy for a fresh project. My idea is to make a better toaster, one where the dial sets the toastedness of the bread rather than the amount of time it's in there for. Setting a toaster using time as the main function is a terrible idea and always has been; it's like your car speedometer working out your road speed by the amount of wind noise.
So I'm looking at ways of getting the Arduino to measure the toastedness of the bread. Measuring colour change is no good - wholemeal bread will only confuse it because it's the same colour as toasted white bread. My first thought went to measuring changes in its sonic reflectivity. Untoasted bread will absorb pulses of sound whereas toasted bread will reflect them.
But I'm having a hard time locating a sensor that can do the job. An ultrasonic transducer would be perfect but the common-as-muck ones only measure range. A homebrewed microphone/speaker combo probably won't withstand the heat.
Is there an industrial sensor solution that springs to anybody's mind?
How about measuring the dryness of the bread? Stale bread would need less toasting than fresh, moist bread. Maybe measure the humidity as it toasts, and when it's low enough it's done?
Also, some people like their toast a lot crunchier than others.
Oooh, that sounds like a great approach. Weight sensor could be kept away from the heating elements. Just need to watch out for a bagel getting jammed down into the toaster slot 8)
A homebrewed microphone/speaker combo probably won't withstand the heat.
I think a short piece of pipe could get your sensor away from the heating elements while "focusing" the sound waves.
But before you get that far, test your concept on cold bread & cold toast.
An ultrasonic transducer would be perfect but the common-as-muck ones only measure range.
The transducers are analog so if you build your own electronics you can measure intensity.
I have no idea if this will work, or if it's better to test the reflection off the toast or transmission through the toast, but it sounds like a fun project. And if it works (and if it's never been done before) you can get a patent and make a bazillion dollars!
wholemeal bread will only confuse it because it's the same colour as toasted white bread.
With any method it's probably a good idea to get a cold/starting calibration every time you start.
I thought about measuring weight - but like time, it's an indirect measurement so I want to avoid it. The true measure of toastedness is crunchyness!
The IR transducers that come with those endless Arduino Starter Kits - (mine has HC-SR04 printed on it) - are hard-wired to measure proximity. Is there any way of getting into the guts of them to control and measure the raw audio data?
I always imagined that an optical sensor would be best. It's the change of reflectivity that's important, not the absolute reflectivity.
Just measure the brightness (with known illumination at an appropriate wavelength) when the toast is started and then watch that change during the toasting process. You could even toast both sides of a muffin or bagel with different amounts of heat to get the equivalent toastiness.
Crunchiness as measured by an analog ultrasonic meter could be good too. You would still be looking at relative changes and not absolutes. Does the back side of a bagel measure a lower crunchiness as moisture is driven away from the front into the back during the toasting?
Hi,
I'd love a high tech toaster, all those sensors, but you missed the main one.
Smoke detector..thats how I unfortunately toasted two crumpets one day.
Also an annoying beeper, a la Microwave, to tell you when your toast is done.
You may have to do some (many) calibration runs.
To setup the range of different parameters you could provide a custom function, where the user puts their bread in the toaster and then manually stops it when the desired crispy/color/moisture is attained.
This would be stored in memory and used for future use automatically.
How about a rod (or rods) that occasionally moves out and pushes on the bread, to see how "stiff" or "penetratable" it is. There's probably a correlation between stiffness/penetratability and "crunchyness." Might need to be calibrated for various types of "bread," tho.
Alternatively, a probe could occasionally scratch the surface; all you'd have to do is listen for the appropriate sound of crunchiness.
I'll take my royalties for these contributions in raisin bagels, thank you.
One thing that has not been part of the discussion so far is the assumption that the slice of bread should be toasted from start to finish in one operation.
Why not to withdraw it from the toaster at intervals for the purpose of testing ?
That would remove the problem of sensors needing to work near the hot and electrically dangerous heating elements.
That won't work with toast. The toasting operation must be uninterrupted for the best toast. The heating process drives moisture from the surface deeper into the toast. If you pause then it will allow some of that moisture to return to the surface, where it must be evaporated away. The toast will end up dry rather than simply crunchy on the outside.
This is opposite to the process of cooking chips (french fries) where a pause lets the moisture re-distribute and you will get the ideal fluffy centre.
He is right. If you want to make bread crumbs you do not tost the bread but heat it to sub tost temperatures for a longer time. This drys the bread without toasting it.
Grumpy_Mike:
He is right. If you want to make bread crumbs you do not tost the bread but heat it to sub tost temperatures for a longer time. This drys the bread without toasting it.
That sounds like a different concept to me.
Toasting clearly needs a high temperature if the surface is to be "burned" before the interior dries out. But I am still not convinced that the entire toasting process needs to be done in a single pass.
And this raises another complication.
Some people like their toast to be crisp right through. Others like the interior to be soft with only the exterior browned.
The other major problems with toasters is that the bread is vertical and the heaters are on both sides. If the heater produces a uniformly distributed heat then the top of the toast gets burned and the bottom under done. This is because of the heat from the lower part of the heater flowing past the top of the toast. Several toasters I have purchased recently have suffered from that problem. In fact I don't think you can actually buy a toaster that correctly handles anything else other than Chorleywood type bread.
