Rendering demonstration of double-limited voltage indicator_Basic hardware circuit diagram explanation

Circuit diagram:

Circuit function:

By setting different voltage intervals, the circuit can realize the dual-limit voltage indicator function.

The entire circuit working process is as follows:

First, we make U1>U2 by setting the voltage dividing resistors R1, R2 and R5, R6.

In this way, when the input voltage Uin is within these two voltage ranges, that is, U2<Uin<U1, both comparators output low level, the transistor is turned off, and the light-emitting diode D1 is in an extinguished state.

When the input voltage exceeds this range, one of the two comparators will output a high level, causing the transistor to saturate and conduct, lighting up the light-emitting diode D1. For example, when the input voltage Uin is less than U2, the comparator U1B outputs a high level; when the input voltage Uin is greater than U1, the comparator U1A outputs a high level.

Therefore, this circuit can realize that when the voltage is lower than the lower limit or higher than the upper limit, the light-emitting diode can correctly indicate it. This is a dual limit voltage indicator function.

Circuit diagram:

Circuit function introduction:

This example circuit can trigger protection when the 12V battery is charged to 14.4V.

The working process of the entire circuit:

The battery voltage changes during the charging process. Lead-acid batteries generally adopt three-stage charging methods: constant current, constant voltage and float charging.

When the battery voltage is above 10.5V, constant current charging is performed. When constant current charging reaches the battery voltage of 14.4V, it is changed to constant voltage charging. When the charging current is less than a certain value, it enters the float charging stage. The float charging voltage can be set to 13.5 V. Of course, these voltage points need to be effectively changed according to changes in ambient temperature.

First, let’s introduce a protection process of the entire circuit:

When a 12V battery is connected, the normally closed contact of the relay is closed and the normally open contact is open. As constant current charging begins, the battery voltage slowly rises from 10.5V. Since the VCC charging input is also connected to the battery, the voltage of VCC will also rise.

When the battery voltage rises to 14.4V, the transistor Q1 is turned on. After transistor Q1 is turned on, current flows through the base of transistor Q2, and transistor Q2 also begins to conduct.

After transistor Q2 is turned on, the current from the collector of Q2 will flow to the base of transistor Q1, thus forming an interlocking form to turn on the relay.

After the relay is turned on, the normally open contact closes and the normally closed contact opens, so that the indicator light connected to B will light up to remind the battery that it is fully charged; at the same time, the connection between VCC and the battery will be disconnected.

However, compared with the previous example, this circuit needs to adjust the resistance of the potentiometer R2 to ensure that the relay can operate at 14.4V.

The adjustment method is as follows:

1. First replace the battery with another type of load, such as indicator light A. Then VCC is connected to an adjustable power supply.

2. Then slowly adjust the resistance of R2, starting from the minimum and increasing it until VCC is 14.4V and the relay operates. Adjustment completed.

However, the charging of the battery in this example can only be carried out to constant current charging, and there are no subsequent float charging and constant voltage charging stages, so there are still some shortcomings.

Notice:

During actual production, according to the different voltage regulator tubes and resistor values ​​you have, you can adjust the circuit parameters of this example accordingly so that the transistors Q1 and Q2 can conduct and the relay can operate.