1
\$\begingroup\$

I am on this project in building food dryer to dry 2 kg fish cracker maximum per use. Based on the calculation, I only need to use power of approximately 60 watt for the heating to achieve the energy required to dry the food. Calculation for power needed for heating element

So, here is my question:

1)Is it possible to have only a 60 watt of heating element to dry 2 kg of food?

2)How can I select for a heating element? (I also use a blower fan to distribute the heat in the food dryer uniformly)

3)If I want the user can enter the temperature that they want(maximum will be 80 degree Celcius), how can I connect the heating element with the knob and Arduino? Here I also use a temperature sensor to detect the surrounding temperature inside the dryer. Block diagram sketch on how the electrical connection works

I am very much a beginner and really have a difficult time in understanding the working principle of an electrical circuit with a heating element. I am aware that the principle is similar to the oven but I dont know how to improvise it since I am using a microcontroller here which I cannot find any commercialized example of such oven in in the market. I really appreciate your help or comment and thank you for helping me.

\$\endgroup\$
  • \$\begingroup\$ Your 60W calculation assumes that the heat is applied to the food in such a way as to rapidly evaporate the water in it. There's no guarantee that just putting food in a warm box will dry it in 2 hours. Also, have you allowed for the air in the box becoming saturated with water? If that happens, drying will stop until someone opens the door. \$\endgroup\$ – Simon B May 15 '18 at 12:19
  • \$\begingroup\$ If this should be MCU-driven, you are looking for some manner of control loop. There's lots of established knowledge in temperature regulation using PID regulators, so I would go with that. You need to establish the necessary accuracy before anything else. Then pick suitable components, like a MCU with sufficient ADC and PWM resolution. I don't understand why you need an external ADC, is it a system with galvanic isolation? At any rate, Arduino is most likely unsuitable. Writing PID regulators on ancient 8 bit MCUs can be done, but it is needlessly painful. Use a 32 bit MCU instead. \$\endgroup\$ – Lundin Feb 20 '19 at 9:13
1
\$\begingroup\$

I would suggest the easiest way of doing this is to modify a cheap oven, if you very crudely turn on and off an oven based on a temperature sensor inside you can get pretty accurate results.

By using a standard oven you do not have to worry about the heating element or the even distribution of heat since this is most likely already taken care off by the manufacturer of the oven.

The easiest way of doing this, is getting a relay, PID controller(or arduino with PID loop), a suitable temperature sensor(maybe a thermocouple) and connect them together. There are several tutorials of people making these products search for "PID Arduino oven" or anything similiar. Here are some results Result 1, Result 2.

The most important part of the build is the PID loop, You set the temperature you want to reach or a curve you want the temperature to follow. The relay will be connected to the mains and turn the oven on and off to reach this temperature. The feedback loop will be the thermocouple sensor, reporting back the temperature to the Arduino or PID controller. PID Loop

| improve this answer | |
\$\endgroup\$
  • 1
    \$\begingroup\$ I've modified an oven like that. The most important part is to leave the existing thermostat in circuit. Set it to your maximum safe temperature, so that should you get a stuck-on failure in your controller (these things happen), the temperature will still be limited. \$\endgroup\$ – Neil_UK May 15 '18 at 10:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.