Heated coaster made with ESP32

Newhor

Heated coaster made with ESP32 [Copy link]

 

The weather was quite cold some time ago, and the water in the cup cooled down too quickly. I saw this kind of 55° heating coaster for sale online, but the price seemed a bit expensive. After learning its principle, I thought about making a heating coaster myself.

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Here is a picture to show the overall effect:

Principle introduction:

Power is turned on to heat the coil the sensor monitors whether the temperature reaches the preset temperature after reaching the specified temperature the MCU's IO port output and MOS tube control the coil to stop heating the sensor detects that the temperature is lower than the set temperature the IO port and MOS tube control the coil to start heating cycle

In order to verify the feasibility at the beginning, I used JLC to draw the first version of PCB, drew a coil of about 4 meters and 10 mils, and used a free board printing. After I got it back, I found that the measured resistance was larger than the theoretical value, and there were errors in the workmanship of the 5 boards in the same batch. So I made a second version and drew a few breakpoints on the coil part, so that I could easily adjust the resistance by adjusting the line length.

Since the function is relatively simple, the main control board uses ESP32-S2mini, which is completely sufficient and the price is not expensive, about 10 RMB. Some other components are some commonly used components, and there is almost no cost.

Since the temperature accuracy requirement is not high, a commonly used thermistor is used. It is inserted into a small hole in the middle of the board in advance and just put down. In this way, the temperature sampled by the sensor is as close as possible to the temperature of the coil heating on the surface of the board. By looking up the table or calculating, the resistance value at 55° can be obtained (you can look up the table for any degree you want), and then the critical point comparison voltage of ADC sampling can be calculated. In this way, a simple code can be written to realize the continuous heating and stopping of the coil near this temperature to achieve a constant temperature effect

In order to see the heating process of the coil more intuitively, four WS2812s are added as indicator lights. Two touch pins are also reserved for switching or temperature adjustment.

Structural aspects:

Four copper studs and 8 flat-head screws are used to fix two identical boards together through the reserved screw holes, leaving space for the components in the middle, so that it can be placed flat on the desktop. However, it still feels a bit light, easy to slide, and the center of gravity is not stable enough. Later, I plan to add some weights in the middle to make its center of gravity more stable.

Let me show you the effect through video:

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User experience:

The heating process is very fast, and the temperature can reach a very high temperature in about one minute. The current insufficiency is that it is OK for heating small bottles of milk, but it is a bit difficult to heat a large cup. The main reason is that the power is too small, only about 5W. I plan to replace the PD chip and increase the power to try later.

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Thank you for reading. If you have any suggestions, please share them ~~~

dcexpert

This is more interesting

qwqwqw2088

It reminds me of the 55° cup from two years ago. It's the same thing.

The word "Fu" on the board is a forum.

It's not PCB silk screen.

Newhor

qwqwqw2088 posted on 2023-2-26 18:47 I remembered the 55° cup from two years ago. It’s different from the “Fu” character on the board. It’s a forum, not a PCB screen print...

It is silk screen, imported from the picture

qwqwqw2088

Newhor posted on 2023-2-26 19:50 It is silk screen, imported from the picture

How to create a logo

This whole picture is pretty cool.

freebsder

It has to be waterproof, what if it spills? Haha.

soso

Not bad, haha, you have to use it quickly. There won’t be so much demand in the summer, and the water cools down too quickly now.

wangerxian

Make a transparent acrylic on the top and add some waterproof shell~ This design is really good~

Newhor

freebsder posted on 2023-2-27 10:09 It should be waterproof, what if it spills? Haha.

Really need to consider this

曹伟1993

The power is a bit small. It seems that the temperature can't rise at all in winter.

dcexpert

soso posted on 2023-2-27 10:59 Not bad, you have to use it quickly. There won’t be so much demand in the summer. Now the water cools too quickly.

It can be used as a cooling device in summer

Newhor

Cao Wei 1993 posted on 2023-2-27 18:05 This power is a bit small. It feels like the temperature can't rise at all in winter

Yes, this one is only 5w, so I plan to try it with a PD chip

damiaa

Using esp32 is a bit higher grade.

nmg

Is there anything special about the design of this heating coil?

It reminds me of an induction cooker. I don't know why, but it always feels unsafe.

Newhor

nmg Published on 2023-3-2 14:18 Is there anything special about the design of this heating coil? It reminds me of an induction cooker. I don't know why, but I always feel it's unsafe

You need to calculate the approximate resistance through the length and thickness of the coil wire, and then calculate the current through the voltage. It is OK within the current range that the wire width can withstand. In addition, the temperature that the PCB can withstand is quite high. The heating temperature can also be controlled through thermistor feedback, which is relatively safe.

Newhor

damiaa posted on 2023-2-28 12:20 Using esp32 is a bit higher grade.

This S2MINI is quite cheap, mainly to add some other small functions

Mzz0528

I want to try making one too.

自负的男人

Haha, I tell you, I found a better design. It's cheaper to make and more clever.

To achieve autonomous temperature control: it is equipped with a cup, and the approximate natural heat dissipation power of the cup at a water temperature of 55 degrees is obtained, and then an electric heating wire that can generate this power is made and attached to the bottom.

Realize automatic start: This thing is designed with a switch, which is a touch switch. Once the cup is placed on it, the switch will be closed.

An indicator light: (It uses a diode light, two wires and two components, this is the part I don’t understand the most)

dukedz

This is what I made in January 2016. I used a ceramic heater and a 5~12V DC adapter. I drank water at night and in the morning. The water was very warm. There was no closed-loop control. . .

Newhor

dukedz posted on 2023-3-15 14:44 This is what I made in January 2016. I used a ceramic heating sheet and a 5~12V DC adapter. I drank water in the middle of the night and in the morning. The water was very warm, without...

It feels good.