Sometimes disorders of cars on the electrical system. Can not be analyzed by the voltage of the battery, always. Using an ammeter to check. It will help to diagnose the problem better. This circuit is an amp meter LED display is not afraid of vibration.
From circuit shown in Figure 1, R1 is resistor that in parallel with the circuit to cause a some voltages that vary according to the consumption of the load. (Up to approximately 133 mV at current 40 A). The voltage drop across R1 is used to extend the differential amplifier A1. Then is sent to the voltmeter circuit. To indicate the magnitude of the voltage. Which consists of A2 to A8.
Figure 1 the schematic diagram of LED Amp meter for CAR
While no current flows through R1, then adjust P1 until the voltage appears at the output of A1 about 6.5 volts. So that Operation of the circuit increase of about D4 to D5.
When a car has a current from the battery voltage across R1 will be higher. The output of A1 will have voltage greater as well, cause LEDs D5 to D8 light smaller or larger depends on power consumption of load. And When there are the current flowing reverse into the battery polarity of the voltage drop across R1, it will change. Make the output of A1 is low. The LED display will switch to using the LED D1 to D10 as the amount of current that flows back into the battery. (Current from the generator in your car)
If we look to see that, this circuit use the system consumes battery as well. Thus, If the battery is very low or very high, the operation of the circuit is wrong. But that’s not a big problem Because the value of a given cycle, it would be an error of 15 percent at the battery voltage of 11 to 15 volts. This can be measured in the car Customizing the battery voltage is 13 volts.
R1 may be used to make a coil resistance using Manganin or Eureka wires. Or wires from the battery to the circuit regulator in a car instead. By connecting the positive terminal of the battery to the regulator circuit in the car directly. Then remove the two poles of this P1 connected across R1 (R1 took out) to the straddle wire instead. Which is the resistance in the wire instead of R1. But it may be too little voltage drop across R1, increasing the rate of expansion of A1 by adding the R6.
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