Injection molding machine current detection circuit

As shown. The IU, IV, IW output signal from the current sensor has a static value of 0V, and an alternating voltage signal (including negative voltage) when it is dynamic, which is not allowed at the MCU input. Level detection circuit, which is responsible for the task of “replacement” of the input signal into a 0~5V DC voltage signal and remove the negative component. The method of pre-adding the DC group bias voltage to the amplifier is often used to complete the negative signal level. "Raise".

In this example circuit, in order to ensure the accuracy of the signal, the 5V output of the reference voltage source device REF195 is used, and the voltage is divided by R90/R91 and R12 to obtain the measured pre-bias voltage of 1.68V, which is input to the non-inverting input terminals of the three amplifiers. Therefore, the static DC level of the 3 output terminals of the amplifier is biased to about 2.3V and sent to the 3 analog input terminals of the MCU.

Injection molding machine current detection circuit

In addition, the IU and IV current detection signals are also sent to the "pulse transmission permission circuit" composed of two sets of window comparators at the same time to cut off U8 (six inverters, used to transmit six inverter pulse signals) power supply when overloaded. To achieve the purpose of improving the protection speed.

When the detection current is within the normal range, the four output terminals of the U7 comparator are in a "high impedance state", R19 provides the base current of Q3, and Q3 and Q4 are in a saturated conduction state to provide working power for the 14 pin of U8. When the amplitude of the IU and IV current detection signal exceeds ±about 6.4V, the output of U7 becomes -15V, and Q3 and Q4 lose their working conditions and cut off (at this time, D5 realizes the clamping of negative voltage to protect Q3), U8 Loss of working power supply, thereby suspending the transmission of pulse signals.

Troubleshooting:

There are no six pulse signals, check U7, Q3 and other circuits;

Abnormal overload alarm during power-on or running, check U9 and U10 circuits.