Hi, I'm working on building a simple instant coffee machine for a uni project. I intend to use a 500W immersion heater and a waterproof DS18B20 sensor to heat the water to a certain temperature, but I'm a bit worried not to fry any components. Are electricity leaks in the water possible with this kind of cheap heater and would that damage my sensor? I would apperciate any guidance.
This is a close match to the heater I'm talking about.
Anything is possible. The probability is extremely small. If the heater has been damaged or mistreated, then the heating element inside the stainless shield might be touching the shield and cause problems. If the DS18B20 also has a stainless shield and it is grounded and the heater also has an electrical problem, then there might be current passing through the water to the sensor ground.
Easy to test with your Ohmmeter before you begin the first test. With both devices powered and ready to test see if there is a low resistance between the two shields.
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I can share this much. The DS18B20 sensors I have are isolated from the sheath but as suggested, I would test what you have. The temp range is fine and make sure you include a 4.7 K pullup between your DS18B20 out and Vcc. I would use a SSR to power your heater element. That or a relay will afford isolation.
Ron
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Those "waterproof" DS18B20 sensors are NOT waterproof at elevated temperatures, the shrink tubing "seal" will fail at near boiling point.
Post a link to that sensor.
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An 18B20 is a sensor, not an actuator. It, under notmal conditions cannot nor will not heat anyting. I am being pedantic on purpose. In electronics accuracy and precision are important.
If the pot is metal be sure it is connected to earth ground, the green wire in the US. Check this link: https://ehs.umass.edu/sites/default/files/Bonding%20and%20Grounding%20Fact%20Sheet.pdf Also look at NEC
take a look at 250.53(A)(8), 250.32, and 250.112.
The heater you linked to is extremely unsafe. It should have the metal part connected to mains ground, and have a thermostat. Both of those are missing. Heaters like that always have a leakage current, which could be several mA. Don't use if you value your life.
Which makes using the heater more dangerous.
Leo..
I agree , I would never use that heater - suprised it’s on sale.
Thank you all for the replies! Could you recommend a safer type of heating element for my project?
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