With the gradual intensification of urbanization, the pace of life in modern cities is getting faster and faster, and people are increasingly reluctant to spend a small number of free time on various household chores, so robots of all walks begin to be born slowly. Nowadays, the intelligent robots visible on the market have mopping machines, dishwashers, and even automatic watering systems have gradually become intelligent.

All these robots have one thing in common, that is, they need a self-service filling system to monitor whether the water in the internal water tank has been filled or leaked. Take a mopping machine, for example, when it is started by the program to mop the ground, it needs to spray a certain amount of water to the ground before it can start wiping, but if the water in the water tank is exhausted, it must be able to detect it, then stop working or automatically alarm, indicating the need to add liquid. Often in such scenes that do not require accurate measurement of the liquid level height, we can only use two photoelectric liquid level switches to start the control function. We install one at the highest liquid level and the other at the zui low liquid level, and then stop water injection once the water level reaches the zui high height. Similarly, when the zui low height is reached, stop the sprinkling action or stop the operation to avoid irreversible damage such as dry burning.

Here, we recommend the photoelectric liquid level switch produced by the original factory of SST, a British company. The model is LLC200A3SH. This product is not limited to power supply. Developers can freely design it according to the actual situation. The end adopts PTFE three-wire system, and the wiring is simple. The outside needs to be equipped with two resistors. The sensor probe is conical. Two materials are available: polysulfone or transparent nylon, and the test is sensitive and reliable.

As shown in the upper right figure, RLED is a current limiting resistor. Its function is to limit the current so as not to burn the photodiode inside the photoelectric liquid level switch. The RPULL-UP is a pull-up resistor to ensure that the output on the green line is always high when the product probe does not touch any liquid. Only when the photoelectric switch is turned on, I .e. the presence of liquid is detected, or the probe touches water, the output level will change significantly, from high to low, and vice versa.

If different power supplies are used, the specific values of current limiting resistor and pull-up resistor can be referred to the above figure or calculated by the following formula. Under normal circumstances, the forward voltage drop of photodiode is 1.3V and the current limiting is 10mA (depending on different liquids). If 5V power supply is used

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