wich kind of battery adapter should I buy? How many days do you think thix can be alive with battery and without charging (device job is simply do a rest request to a website and switch on/off the valve)
do you think i can add a solar charger to the device? Which kind do you suggest?
Any reason why you’d need a 9V battery? LiPo batteries might be better suited for this.
The valve you picked worked on 12V, whereas you’d only have 9V available. You’d thus have to transform that to get to 12V which isn’t the most efficient. Ideally you’d find one that runs on 5V or 3.3V since that’s what the Photon uses as well.
As for how long i’d be able to run, that depends on the capacity of the battery. Unfortunately, WiFi is inherently power hungry, and due to the nature of your projects, sleeping isn’t really an option. That’d mean it’s on continuously, which doesn’t do wonders for battery life I’m afraid.
Charging it with solar; The reason why I asked about the kind of battery is because Particle has this nice Power Shield available with a LiPo which should make that part a bit easier.
@dynamica, also your solenoid will take a LOT of power when it is energized unless you use a latching solenoid or motor activated valve which only consumes power during switching. As for a solar charger, your panels would need to produce enough to power the Photon AND charge the battery.
@Moors7, the power shield is a very interesting solution, even though the small sparkfun solar charger is no longer for sale! Any other solar charger on the market can work as well? Do you suggest any in particular?
Nothing wrong with Particle power shield, but it doesn’t include a solar cell. The power shield on the Particle store includes the shield itself, a 3.7V, 400mAh Li-Po battery and headers (but no solar cell).
Assuming he first transformed it up to the required 12V to switch the valve, yes, you could use a voltage divider to get it down to 5V. Unfortunately, that’d mean you’d be losing 7V through the resistor, which is far far from efficient. Even a simple voltage regulator could do better than that, though a buck converter would be better.
Tl;d’r, yes, but it might not be the best idea…
@benjiiiiuk, I would not recommend a step-up regulator for supplying the valve motor. Instead, use a 12v battery pack and use a step-down (buck) regulator for the Photon and control the valve with a power MOSFET. Using resistors or even an linear regulator (eg. 7805) will be much less efficient that a buck regulator. Polulu has some great units.
Step-up regulators are not efficient? Because I found a 50000mAh power bank with an embedded solar cell
that I think could power the Photon via USB, without worrying about frequent manual recharges of the battery.
In this case i would need something to amplify the voltage coming from Photon’s GPIO pins, cause i cannot connect the valve directly to the battery.
If a step-up converter is not the right solution, what’s better?
@dynamica, you could use a 5V valve instead of a 12V unit and not require a step-up regulator at all! The battery pack would supply both the valve and the Photon. You would just need some MOSFETS to control power to the valve via GPIO pins.
The 5V valve seems to make a lot of sense. I would look at the CR02 or CR03 version as these would not require an H-bridge.
A H-bridge or a DPDT relay allows one to drive a 2-wire device with either a negative or positive pulse. Latching solenoid devices (including the ones above) typically need a + pulse to open and a - pulse to close.
Another option would be to hack a commercial hose bib single valve irrigation timer and replace any brains found with the Photon…