Zedman
Full Member level 6
I made an MCU controlled injection mold driving. It controls solenoids according to a specified flow and inputs.
All inputs are protected with transient supressors, the solenoid switcher FETs are separated with optocouplers no galvanical connection with controlling part.
It runs on a 220V->6V 300mA transformator and a 7805 with buffer cap, and a separate DC24V input for the solenoids.
It has a small control panel which is about 30cm away from the main PCB and connects with a 16 pin ribbon like cable. It holds a 4x20 LCD, 10 buttons and a beeper.
From time to time I notice garbage on the LCD. I placed some pF capacitors to the RW/RS/E lines, and now modified the program to reinit the LCD before write onto it, now it's better but not perfect.
The machine pumps hidraulic system with an 5kW motor and when this stucks a bit and the solenoid releases the fluid I suppose it generates some spike on the power lines which causes
the LCD to receive garbage, and it could and it did even freeze the MCU.
Also there is an other solenoid which releases an air solenoid which blows down the item from the tool, this is also 220V operated and also does the same as the motor.
What could I do to eliminate these freezes and interferences?
Are these coming from the 220V side though the power lines and to the MCU's 5V or it's an EMI like thing getting into the chip through it's other pins?
Where should I search?
any idea is appreciated,
thanks,
Zedman
All inputs are protected with transient supressors, the solenoid switcher FETs are separated with optocouplers no galvanical connection with controlling part.
It runs on a 220V->6V 300mA transformator and a 7805 with buffer cap, and a separate DC24V input for the solenoids.
It has a small control panel which is about 30cm away from the main PCB and connects with a 16 pin ribbon like cable. It holds a 4x20 LCD, 10 buttons and a beeper.
From time to time I notice garbage on the LCD. I placed some pF capacitors to the RW/RS/E lines, and now modified the program to reinit the LCD before write onto it, now it's better but not perfect.
The machine pumps hidraulic system with an 5kW motor and when this stucks a bit and the solenoid releases the fluid I suppose it generates some spike on the power lines which causes
the LCD to receive garbage, and it could and it did even freeze the MCU.
Also there is an other solenoid which releases an air solenoid which blows down the item from the tool, this is also 220V operated and also does the same as the motor.
What could I do to eliminate these freezes and interferences?
Are these coming from the 220V side though the power lines and to the MCU's 5V or it's an EMI like thing getting into the chip through it's other pins?
Where should I search?
any idea is appreciated,
thanks,
Zedman
