A New Refrigerator Controller

I saw a "new generation refrigerator and freezer controller" in the electronics market. This product does not use temperature measuring components, but achieves constant temperature by changing the power on and off time. The price is only a few yuan, so I bought one. After using it for more than a month, I feel that the performance is quite reliable, and the theoretical calculation shows that the energy saving effect is obvious. So I drew its circuit based on the actual product as shown in the attached figure.

The AC220V voltage is limited and reduced by C1 and R1, rectified by D1~D4, and filtered by C2 to obtain a 9V DC voltage for the relay J coil to work. The voltage regulator diode D6 and the resistor R10 form a 5V voltage regulator circuit to power the IC MX0230. Analysis shows that IC should be an integrated block with dual timing functions. The time constant is adjusted by w1 and w2. An intermittent control pulse is output through pin ① to control the on and off of the relay, thereby determining whether the output socket cz is powered or not, and realizing the power on or off of the refrigerator and freezer.

When in use, plug the refrigerator into the output socket cz of the controller, adjust the resistance values ​​of w1 and w2, and change the time of turning on and off the refrigerator. The adjustment range is 5 minutes to 20 minutes, which can be determined according to the performance of the refrigerator and the nature of the food stored. For example, in normal use, the start time is 10 minutes and the shut down time is 30 minutes. When wrapping dumplings and freezing them quickly, the start time is 60 minutes. After quick freezing, put them into food bags, and then the start and stop time can be restored to the normal use state.

Since this controller cuts off the power of the refrigerator according to the time, the quality of the original thermostat in the refrigerator has lost its meaning, so you only need to turn the temperature control dial to the maximum number, that is, the "normally on" position. The thermostat of my refrigerator failed. In the past, it was always turned on for 40 minutes and off for 10 minutes. The upper and lower boxes were both frozen, wasting energy. After using this controller, the on and off time was reversed. Calculation shows that it even saves more electricity than a new refrigerator.

It is thought that this controller can be used not only to control refrigerators, freezers, and electric fans, but also to control more types of higher-power equipment that require intermittent operation, such as large three-phase ventilators, by adding a relay to expand the contact current.