555 multi-temperature test circuit configuration

  
As shown in Fig multi-channel temperature measurement circuit. The test circuit consists of a core consisting of 555 one-shot delay circuit. When the button i
555 multi-temperature test circuit configuration - schematic

s pressed AN, IC1 (555) due to the occurrence of low feet set, high pin output relay J1 pull, the corresponding thermocouple channel is turned on. Meanwhile, LED LED1 lights. By R1 and capacitor C1 is charged, when the charge voltage on C1 to make foot potential reaches 2/3VDD, the 555 reset occurs, low back pin output by 0.01 mu F after capacitive coupling pin was low so IC2, IC2 occurs is set. Output level corresponding turns on the second thermocouple, repeat the process, so in turn trigger, multi-channel temperature testing. If the circuit closes the switch K1, the cycle can be detected, and each stage of the measurement time (delay time) is td 1.1R1C1, icon parameter corresponding to a delay of about one second. Taking measurements at the same time, LED lights, for detection indication. On the circuit diagram (a), when the power-up may occur a few light-emitting diode LED flicker at the same time, therefore, can be used as shown in (b), improved circuit. After accessing R, C network, when turned on, since the C voltage can not change suddenly, so that 555 (Ic) reset terminal ( feet) in forced reset state, pin output low, the capacitor C is charged with the conduct, feet potential gradually rises when foot potential rise to the high level, Ic at all levels in the timed waiting state, thereby improving the accuracy of the test circuit. This circuit is used when the multi-channel temperature testing, switch the thermocouple corresponding channel.




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