In the operation of the microcontroller the flow of fuel, the description of which published in "Radio", 2001, No. 11, pp. 32-34, it was found that after switching off and then switching on the ignition of the vehicle accumulation device the volume of fuel consumed sometimes distorted and led the displays appear completely unexpected numbers. The reason for this is too the slow decay of voltage in the on-Board network, comparable in speed with the decline the voltage on the capacitor C3 of the flowmeter. This situation arises, for example, if the onboard network of the car is connected USC or another user with the big capacitors in the power supply circuit.
To eliminate the defect, simply install the flowmeter detector lowering voltage CRP connected according to the scheme shown in Fig. 1.
Now the diode VD1 of the flow meter is no longer needed, it can be replaced with a jumper. When the supply voltage decreases below its threshold (7.3 In) detector will signal the microcontroller. The latter will receive sufficient at any speed change the vehicle voltage sufficient time to perform write operations accumulated data in the internal non-volatile memory.
Chip CSP can be substituted with a lower threshold. In Fig. 2 shows how to connect, for example, the detector CROP.
Need the value of the threshold voltage set selection resistor R1.
Author: A. Long, Moscow