Will the puck.js be able to power a relay?

Hi - either direct from the puck, or, from a separate battery/relay (controlled by the puck) - i'd like to be able to power a latching relay so that I can have a remote control for my sprinkler.
http://www.hunterindustries.com/support/node-using-dc-latching-solenoids-battery-controllers

My cell phone will come within bluetooth range of the puck, and, i will either engage or disengage the relay to turn the water on or off.

Is this an easy build? Can someone guide me?
Thanks! Mike

Hi Mike,

Directly, Puck.js might be able to power a very small relay (it'll provide 10mA per pin), but it's not such a good idea to drive anything inductive from it. You can get relay modules really cheap though: http://www.espruino.com/Relays

These have 1 or 2 relays, plus optical isolation - and look like they'd be perfect for what you want, and easy to wire up. You'd still need a biggish battery to power the solenoid, and you could just plug the relay into that as well.

There are other options too - for instance you could use a motor driver. They tend to be totally solid state, and you can get those on little modules with screw terminals for a few dollars too.

... but yes, it should be a pretty easy build. For the solenoid I guess you need to turn it on one way and off the other which means one more wire, but it's only 3 or 4 wires needed to the Puck (depending on the relay module), GND, power, and 2 signals.

It depends how long you have your sprinkler on for... I water the plants here with an Espruino and use a non-latching solenoid. With it on 4 times a day for 60 seconds, a smallish lead acid battery lasts for ages.

What about a Triac with opto-isolated driver (Diac) ...to stay out of any 'solenoidy' thing?

I assume the sprinkler valves are AC driven... and you want to pull only two wires to the puck. With that setup you could use the off time to recharge a rechargeable power supply for your puck Just make sure the current is low enough to not make the valve solenoids switch. The off with low current vs. the on with 'high' current would still provide ample positive power balance...

@allObjects yes, if you're willing to do mains, a triac or solid state relay module would work great! A triac won't draw much power so I doubt there's any need to recharge the Puck.

I can understand if the idea of water + AC volts isn't very appealing though!

Your comment about appeal is taken... but: it is what it (prevailing) is: not mains, just 24V AC (from cheap main wall outlet transformer, no rectifiers needed). The 24V allows decent low current wires (high gauge). All timers have a battery to keep time on power interruptions (and to keep program, if not yet stored in EEPROM). First timers were electromechanical: shaded pole motor with gear related AC frequency and on/off cams... all run by 24V to avoid mains challenges... and you still can buy them... because they are extra sturdy, run (almost) for ever, and most important: 'maintainable' with basic tools (and basic knowledge).

Wow, yeah, 24v AC would be great - and would work perfectly with a triac. I wasn't aware they did that (we don't generally need to water our lawns in the UK :) ).

Hi @Gordon and @AllObjects - thank you.
With your advice - I'm pretty sure I would be able to do this build with a DC relay module using the (less-preferred - due to I already have 24VAC solenoids) latching DC solenoid valves.

Can you please share some more details about the TRIAC approach, and, how I can achieve the same objective (wireless control of solenoids)?

I wonder how you would recommend that I get 24V AC to the solenoids? Maybe http://www.powerstream.com/inv-12dc-24vac.htm?

What would be the best way to keep the price low if I wanted a single puck.js to control a single solenoid (either 5VDC or 24VAC)?
Maybe there is a less-feature-rich version of puck.js which would have only one or two outputs (for powering the relay)?
Maybe I could use 24VAC to power the puck.js?
Maybe something be integrated onto puck.js so that it could also supply 24V AC (providing a sufficient battery is used) - thereby reducing the number of moving parts.

@Gordon - Is there a version of puck.js which I could purchase now that would satisfy my solenoid needs? The Esprunio is a bit more feature-rich than I need.

Many thanks!

Is there a version of puck.js which I could purchase now that would satisfy my solenoid needs?

You could buy a micro:bit or an nRF52 devkit, but that's about it for the moment... It'll be a while before I get enough free time to start thinking about making some other Bluetooth LE device!

You could try getting one of those cheap Smart Bracelets and flashing Espruino on it like on this post though it is likely that you'll receive something very slightly different with a chip that Espruino doesn't support :(

I've tried this before and been unlucky, but soon I'll be trying it again, I'll probably buy this one.

@user67097, can you be more specific about the specifications of your valves? This kind of defines the path to the solution. Simple valves- as I assume you want to control, such as from Genie or Toro, are generally drive by 24V AC, even tough they are DC compatible as well. May be you have totally different type of valve you want to control.