Earlier, we have an article about the choice of electronic lock battery. However, the choice of electronic lock battery is only a hardware foundation, and the longest life of the battery is achieved. The core method is the reasonable design of the CPU program.
In general, the circuit of the electronic lock operates at a normal standby current of 1 mA (excluding the operation of the motor, the buzzer sounds, and the light is on). According to this power consumption calculation, the 3-cell alkaline battery can continue to work for more than one month. But for electronic locks, this is obviously far.
In terms of power consumption, our design goal is to install a 3-cell alkaline battery for one year or more.
From a technical point of view, the main way to save electricity is to control unnecessary power consumption. Through analysis, we found that locks do not open and close operations most of the time, and minimizing power consumption during this time is the key to achieving design goals.
There are 2 technical methods that can be used for power consumption control: polling mode, triggering wake-up mode.
The process of polling mode is as follows: the program commands the CPU to enter the sleep state. Each interval (such as 1 second or 0.5 second, the specific time interval is related to the CPU model and actual operation requirements), the program automatically wakes up the CPU to detect whether there is a legal identity. Only the button or RFID card needs to be read, if it is, then enter the identification--interpretation is whether the switch is normally closed--the work ends and continues to sleep--so reciprocating, if there is no further progress to sleep. The power consumption during sleep is typically a few nA.
The process of triggering the wake-up mode is as follows: the program is in a sleep normal state, and once an external trigger event occurs, the program is automatically woken up and enters a normal working state: identification--interpretation of whether the switch is normally closed--the work ends and continues to sleep--such reciprocating.
From this, it can be seen that the polling method achieves basic power saving, but it is better to trigger the wake-up mode completely.
For TM (smart button) mode identification, you can choose to trigger the wake-up method.
For RF-based identification, because it is non-contact, the CPU cannot be made to perceive circuit changes, and polling is generally used.
There are also some manufacturers that use infrared detection to determine whether an RFID card is close to the lock body to achieve wake-up of the program. There are two disadvantages in this way. One is that the infrared detection component will increase the power consumption, and the other is that any object approaching the lock body will trigger the infrared, causing the program to wake up and increase power consumption.
It is very gratifying that we can also control the basic power consumption of the polling at the nA level in the polling mode, so that the polling power consumption and the sleep power consumption are basically the same. Design goals for long battery life without increasing costs.
In addition, it should be noted that only the design of the program part is not enough, and the low-power design of the peripheral circuit is especially critical. The reasonable design of both the program and the external circuit is the indispensable solution to the power consumption problem. Aspect.
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