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As a student, I'm currently working on a science project where I intend to connect a 12V, 2A solenoid valve to a relay and subsequently to a Raspberry Pi Pico. The solenoid valve is powered by a 12V, 5A source. Despite installing two 1N4001 flyback diodes, I'm still experiencing sparking issues with the solenoid valve.

I've verified that the flyback 1N4001 diodes are functioning properly. Upon watching videos of others facing similar issues, I've noticed that the sparks I'm experiencing are larger than theirs.

For my project, the valve needs to be open for a few seconds and then closed again.

Could anyone please provide insights into why this issue might be occurring, what I can do to mitigate it, and if there are any alternative solutions I could explore?

The valve I am using.

Sparks:

enter image description here

Circuit diagram:

enter image description here

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    \$\begingroup\$ draw a schematic (there's a schematic editor built into this board, the diode/resistor button), showing the power supply, switching element, solenoid coil, and diode. It's not clear from your photo where you have connected the diode to. \$\endgroup\$
    – Neil_UK
    Commented Feb 13 at 14:00
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    \$\begingroup\$ Your diagram shows what you should be doing. But your photo appears to show something different ... \$\endgroup\$
    – brhans
    Commented Feb 13 at 14:57

3 Answers 3

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The photograph and the pictorial do not tally.

The photograph shows the flyback diode wrongly wired across the power supply terminals.

The corresponding schematic is as follows.

enter image description here

On the other hand the pictorial shows the flyback diode correctly wired across the valve solenoid.

Here's the appropriate schematic.

enter image description here

With the flyback diode wired across the valve solenoid, there should be no spark when it is de-energised by opening the relay contact or by disconnecting the wire.

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  • \$\begingroup\$ Huge thanks for your comment! Just wanted to update you that I've managed to enhance my circuit. NOw there are no more sparks, everything's functioning perfectly. \$\endgroup\$
    – Tanmay Sonar
    Commented Feb 14 at 10:41
  • \$\begingroup\$ Hi Tanmay, Thank you for the update. I'm glad you could solve your problem. \$\endgroup\$
    – vu2nan
    Commented Feb 14 at 13:11
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schematic

simulate this circuit – Schematic created using CircuitLab

The diode should be connected across the solenoid, not the power supply.

In the photo supplied you seem to be touching the solenoid wire to the power supply / diodes.

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  • \$\begingroup\$ Thank you so much for your comment! I truly appreciate it. I'm happy to report that I've improved my circuit, and now everything is working flawlessly without any sparks. Your support means a lot! \$\endgroup\$
    – Tanmay Sonar
    Commented Feb 14 at 10:40
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It will spark if you disconnect the valve from the diode with the wire like that, because 2A needs to flow somewhere to discharge the stored magnetic field, and the voltage will jump to very high value until the air breaks down and the spark allows current to flow and the energy to be dissipated.

If you want it to not spark, you will leave the diode to the valve side while disconnecting the supply from the valve+diode side.

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  • \$\begingroup\$ Thank you a bunch for your feedback! I'm excited to let you know that I've improved my circuit setup, and now there are no sparks in sight. \$\endgroup\$
    – Tanmay Sonar
    Commented Feb 14 at 10:42

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