Small tester circuit diagram

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

Working principle: +9V power supply is regulated by ICl (7805) and output +5V as the working voltage of the whole tester. LED1 is the power indicator. IC2 (LM324) is an operational amplifier. The inverting input terminal (2) is connected to the upper and lower bias circuits formed by R2 and R3. The voltage of this terminal is about 25V. The non-inverting input terminal (3) is externally connected with "optocoupler" IC3 ( TL621), phototransistor ce pole and R4 into the upper and lower bias circuit. Usually, the phototransistor in IC3 is in the off state, so the voltage of IC2(3) is Ov, (1) the pin outputs low level, LEDA does not light (light emitting diode); when the initial end of IC3 A+, A- has current, The phototransistor is turned on and is in a low resistance state. When the IC23 pin level is higher than 2 feet, the amplifier flips, 1 pin outputs high level: one way lights up LEDA; the other way is fed back to IC23 pin via Dl, the comparator enters self-locking state, LEDA keeps bright. C2 acts as an anti-interference. The value of R4 determines the sensitivity of the amplifier. According to the value of the icon, as long as the voltage applied to the A+ and A- terminals is not less than 1V and the current is not less than 60uA, the output state of the amplifier can be triggered to flip.

IC2 selects LM324 and contains four operational amplifiers to form four sets of identical test circuits. If the test circuit is needed, the number of components such as the integrated block can be increased to form a plurality of test circuits. IC3 uses linear "optocoupler"

It can be (such as TLP621). The +9V power supply uses a laminate battery for easy portability. Ports such as A+ and A- can be extracted by a flexible cable.