TRIAC T435-600B issue with solenoid pump and diode

Question

I'm currently facing an issue with controlling a solenoid pump using a T435-600B TRIAC in a configuration that includes a diode.

The power supply for both the TRIAC and the pump is the same, and it's triggered by an opto. I am unable to control the pump when the diode is connected in series with the solenoid pump coil (connected at JSx5).

However, when I tested a similar setup with a solenoid valve and without the diode, it worked as expected. Could it be the phase shift between voltage and current due to the coil of the solenoid?

I'm not sure what is causing this issue or how to resolve it. Has anyone encountered a similar problem or have any suggestions on how to troubleshoot this situation? I'm open to ideas and solutions.

Answer 1

I am sharing the solution I found for this problem. The problem comes from the phase shift of voltage/current due to the coil and the diode, as well as the non-zero-crossing optocoupler. The triac is activated by current, and with the phase shift, it activates in the middle of the sinusoid. Due to the zero-crossing photocoupler and the half-wave caused by the diode, there is not even a quarter of a wave left to power the coil.

To solve this problem, I have found several solutions:

• Place a return diode with a resistor (very bad idea)
• Replace the triac with a relay (good idea, but not in my case)
• Replace the optocoupler with another zero-crossing one (bingo!)

I hope this can be of some help to someone.