Working mode: positive pulse open valve, negative pulse off

[donburch888 (Don Burch)]

I have located a Latching Solenoid Valve with specifications including:

• Working voltage: DC 4.5V
• Working mode: positive pulse open valve, negative pulse off
• Pulse width: 30ms

Is there an existing module which can connect to ESP32 and provide +ve and -ve pulses ? I'm not into electronics (and at 66 not here to become a professional electronics engineer) and I don't trust my soldering - so an off-the-shelf module would be preferable.

I have been trying to figure this out but need a hint, or preferably a pointer to a explanation/tutorial.

Thanks in advance

[IOT7712]

Two wires. When it is positive, it is on. When it is not positive, it is off?

High inrush current. Kept open/closed by water pressure.

Sounds a bit different to what you want for battery operation.

ESP32 reboots when reading voltage from INA219

I'm not sure whether I have faulty hardware or have missed something in the configuration... I am adding a water sprinkler to my greenhouse ESP32. The solenoid is 12V but adafruit advise it works down to 6V. I don't want to drain my main LiPo by holding the solenoid open so thought I would use a common 9V battery for this - and of course to monitor the 9V battery voltage. I already have an INA3221 monitoring my LiPo voltage, and the INA3221 states it works up to 26V, so have wired it all up …

Thought it looked a bit familiar - why not continue in your existing thread?

[donburch888 (Don Burch)]

@IOT7712

why not continue in your existing thread?

Because in that thread I was using a Latching Relay which interfaces with ESP by two Grove 3-pin connectors (for switching to A or switching to B)

and a regular Solenoid Valve ... pretty easy to program in ESPHome ... and then another user asked

@Karosm

Why don't you simply use latching solenoid like all commercial battery powered irrigation systems do?

MUCH less power required to do the latching at the Solenoid ... and so off down that rabbit-hole ... but I only found some on aliexpress which have two wires and look like this

I started a new thread since this seems a very different piece of hardware and I didn't wish to confuse the two issues - especially since I may need to go back to the other thread if this Latching Solenoid Valve doesn't work out.

---

Back to the Latching Solenoid ...

I understand that a regular relay or solenoid needs power applied to turn ON and hold it ON, and opens the contact immediately the power is removed effectively turning it OFF. I guess this is what you mean by "When it is positive, it is on. When it is not positive, it is off".

However a latching relay stays in its current state when the power is off. I assume that "positive pulse open valve, negative pulse off" is requiring a +4.5V 30ms pulse to open the valve, and a -4.5V 30ms pulse to close the valve. In effect a +ve voltage is when the electrons flow in one direction, and -ve voltage is when they flow in the other direction

Continuing down the rabbit-hole I think "DPDT relay" and "H-Bridge" are the keywords I need.

[Karosm]

Latching solenoid needs polarity swap, not negative voltages. Motor driver would be my choice to drive them since they have built-in flyback handling and protection circuitry. Relay doesn't.
TB6612FNG could be good choice here (I don't know your valve coil specs though). You can get those from AE for $1.

Ps. for next time, consider using battery powered irrigation timer as hardware and just replace the controller with Esp. For about $10 you get all hardware in convenient enclosure.

[donburch888 (Don Burch)]

@Karosm

Motor driver would be my choice to drive them since they have built-in flyback handling and protection circuitry. Relay doesn't.

A very important feature for me.

@Karosm

TB6612FNG could be good choice here

And a little research reveals the seeed studio Grove - I2C Motor Driver (TB6612FNG) which has a easy-to-use i2c interface and even an ESPHome component. Maybe that's too easy ! Thank you Karosm !

But my local supplier only has seeed's earlier Grove L298N Motor Driver board ... which looks as though it should be driven with the ESPHome H-bridge Fan component.

Still more to research.

[Karosm]

H-bridge fan is compatible with normal TB6612FNG (not I2C) and L296N but you don't even need that for simple polarity swap . You can use two gpio switches on driver IN1/IN2 pins to change direction (polarity). L298N is really antique and inefficient while TB is more modern mosfet driver.