DIY Constant Temperature Wax Melter

The constant temperature control circuit introduced below has a temperature control range of 50℃-120℃. If the electric heating element is sewn on the heat-resistant cloth with electric heating wire, and the electric heating cloth is attached to the outside of the plastic container, it can be made into an electric heating container. The temperature of this electric heating container is adjusted to a suitable value, and skin care wax is placed in the container. After the wax melts, it can be used to soak hands and feet, which can have a good skin care effect, especially for some people in the northern region with dry and cracked foot skin. Interested readers can try to make it according to this circuit.

The principle of this circuit is very simple. It uses one side of the dual op amp LM393 as a comparator. When the temperature is high, the op amp U1 outputs a low potential, and through D6, the control electrode of the thyristor SCR1 is pulled down to turn off the thyristor. (Note: When the SCR control electrode is pulled low, it seems that the SCR cannot be turned off).

The component parameters of this circuit are as follows: IC can use any type of ordinary dual op amp or single op amp, such as 358; VR2 is an adjustable resistor, connected to the PCB, pre-adjusting the temperature value; VR1 is a potentiometer, which can be installed on the control panel for users to adjust the temperature at ordinary times; TR1 is a thermistor, and the author uses a common temperature type thermistor from Sanjing Sensitive Component Company, whose resistance value at 25℃ is 24kΩ; TF1 is a temperature fuse, whose melting point should be 1200C ~1470C, and the current ≥5A; During installation, it is important to pay attention to the good contact between the thermistor and the temperature fuse seat of the basin body. The method is to use two small plastic sheets, stick them to the flatter place outside the basin body, and leave a groove in the middle of the two plastic sheets, the size of which is just enough to put the thermistor or temperature fuse. After placing it, use silicone to seal the two components firmly. The thermistor is placed away from the heating wire, but at 2/3 of the height of the wax liquid. The temperature fuse should be about 3 to 5 cm away from the heating wire on the outside of the shell, and it can be just close to the plastic. In addition, please note: 1. When testing, water or wax must be put into the container to avoid burning; 2. The container should be well insulated. The safe way is to unplug the power supply after the wax melts before using it.