I have a 12 V 18 W (1.5 A) solenoid valve that I want to control valve with an RF relay.

I use a Sony 18650 li-on battery to power this system. A 1S 10 A BMS unit is protecting the battery.

Even though I put a diode between the input legs of the solenoid valve, when I close the relay (valve is connected to the NO-normally open input), the relay turns on and off momentarily. It cuts the circuit as if there is a short circuit in the valve. Is there any component I should add?

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  • Battery: SONY VTC5 18650 3.7 V 2600 mAh (30 A Discharge)
  • BMS: 1S 15 A 3.7 V 18650
  • Voltage regulator: XL6009E1 3-32 V - 4 A
  • RF relay: 1 channel 433 MHz wireless RF relay
  • Current values: 10 A (28 VDC) - 10 A (250 VAC) - 12 A (125 VAC)
  • Solenoid valve: 12 VDC - 18 W
  • Diode: 1N4007
  • \$\begingroup\$ Link to the RF Relay module? It might be designed or configured to make a short output pulse rather than holding the relay on continuously. \$\endgroup\$
    – AnalogKid
    Nov 26, 2022 at 12:41
  • \$\begingroup\$ Hi, forgot to mention; When the solenoid valve is no connected, the relay opens and closes when I press the remote button, and I can keep it open for as long as I want. \$\endgroup\$
    – A.O.92
    Nov 26, 2022 at 13:26

1 Answer 1


I should test following points:

Make a jumper in relay contact to activate valve and measure 12 Vdc supply is Ok. If not the power supply is not correct.

Disconnect solenoid valve and check if relay can hold the contact closed when you activate RF module.

If both are Ok, it could happen that the power supply cannot hold the voltage when you activate the valve because the current step, and the voltage drop can reset the RF module. This can be solved with additional capacitors in 12 Vdc (if too much you will have high inrush current when switching on power), or only feed the RF module by a diode and capacitor to prevent the 12 Vdc voltage drop to reset this circuit.

enter image description here

  • \$\begingroup\$ Hello, I checked the whole circuit before connecting the solenoid, all the points that should be 12V are 12V. Also, when I deactivate the solenoid valve, the relay works normally. When I press the button, the circuit is closed, when I press it again, it turns on. Regarding the capacitor connection, do you know the value of the capacitor I should connect? \$\endgroup\$
    – A.O.92
    Nov 26, 2022 at 13:28
  • \$\begingroup\$ It depends on current and voltage drop that electronics can support, try C2 = 470uF (min 25 V), D1 = 1N4007. \$\endgroup\$
    – Bravale
    Nov 26, 2022 at 15:48

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