Re: [beagleboard] Relay Modules for Sprinkler System

[Andrew Bradford]

On Fri, 18 Jan 2013 07:58:42 -0800 (PST)
pbor...@gmail.com wrote:

> A group of friends and I are trying to build an automated sprinkler
> system with the BeagleBoard-Xm and we ran into a wall. We hoped you
> guys might have any advice.
>
> Basically we wanted to use our board to control the siphon valve on
> the sprinkler system. That doesn't seem too hard, but the board
> cannot provide enough voltage to switch the valve on. We thought
> about using a switch or relay module that would basically allow the
> 24V or however much voltage we need to go to the valve. Would anyone
> know which relay module would best be suited for this? Or any other
> suggestions would be helpful as well!

Do it in stages, beagle drives a FET which drives the relay. The FET
is low-side (source connected to ground) and the high side of the
relay's control goes to a 24V (or similar) source. The relay can
switch your system's actual power (the sprinkler siphon valve or
what-have-you) at what ever voltage that needs. Just pick a relay that
can handle switching your load on-off-on.

If you're able to use 12 V relays, your local auto-parts store has a
bunch in stock that can handle quite a lot. Usually they're pretty
cheap.

If you tell more about what your components are, such as links to
specs (with voltage, current, etc documentation in them), we'll be
better able to help.

-Andrew

[David Lambert]

On 01/21/2013 09:01 AM, pbor...@gmail.com wrote:

Hi Andrew,

Thanks for your reply! Im not quite sure I understand how the beagleboard will provide enough power,

The Beagleboard will have enough power to drive a FET, which will power a relay, which in turn will power the valve. If you do not use a solid state relay, put a reverse biased diode across the coil to protect the FET from any back EMF. Also it would be prudent to put some transient protection/noise suppression on the relay-valve circuit.

Just my 2 cents. :-)

but I sincerely appreciate your help. 

As for the components, we only have the beagleboard-xM and the valve so far. Here is the valve that we have bought: http://www.orbitonline.com/products/Valves/02/16/07/1826/ it requires 24V but I know we would be able to buy a replacement solenoid where the required voltage is about half of this one. 

I have been trying to look online for relays like at radioshack, but im unsure which would be a good fit. PLease, advise.

Thank you!

-Patrick

--
For more options, visit http://beagleboard.org/discuss
 
 

[Andrew Bradford]

On Mon, 21 Jan 2013 09:11:16 -0600
David Lambert <da...@lambsys.com> wrote:

> On 01/21/2013 09:01 AM, pbor...@gmail.com wrote:
> > Hi Andrew,
> >
> > Thanks for your reply! Im not quite sure I understand how the
> > beagleboard will provide enough power,
> The Beagleboard will have enough power to drive a FET, which will
> power a relay, which in turn will power the valve. If you do not use
> a solid state relay, put a reverse biased diode across the coil to
> protect the FET from any back EMF. Also it would be prudent to put
> some transient protection/noise suppression on the relay-valve
> circuit.

Yes, exactly this.

A relay like [1] would probably work.

[1]:http://www.digikey.com/product-detail/en/G3MC-201PL%20DC5/Z2521-ND/368909

What you'll need is a 24 V AC source, as that's what your sprinkler
says it needs. You use that 24 V AC source going to the solid state
relay which acts like a light switch (you can use an actual light
switch to prototype, if you want).

The low voltage control input to the solid state relay will need to
have +5 V on one side of the solid state relay input and a FET on the
other, with the FET source connected to ground and the FET drain
connected to the solid state relay. You'll want an N channel FET with
a gate voltage less than 1.5 V if you're using an xM (you could get
away with a 2.5 V FET gate with a bone).

The xM drives a GPIO which turns on and off the FET. The FET turning
on and off turns on and off the relay. The relay turning on and off
turns the sprinkler on and off. Due to the difference in power and
voltage levels required, you have to do this in stages.

-Andrew

[Dan Hockey]

how 'bout a usb relay board

https://www.sparkfun.com/products/9669

[David Lambert]

On 01/21/2013 09:42 AM, pbor...@gmail.com wrote:

Thanks for the description, David! It makes sense now. However, how would I put transient protection/noise suppression on the relay valve circuit if I may ask?

There are many ways of doing this. Personally I would use suitable MOVs (http://en.wikipedia.org/wiki/Varistor) across relay contacts that drive inductive loads. Also make sure that the ground currents cannot flow through any sensitive circuits; a single point star configuration is what I have used in the past.

[raysho...@gmail.com]

Hi, I found this Google group through search. Just to let you know that I've recently developed a sprinkler / irrigation extension board for the BeagleBone Black and you can check out the details at http://beagle.opensprinkler.com. Technically, it uses triacs (AC transistors) to control sprinkler valves, and it has per-station bidirectional TVS for protection against transient voltages. Triacs are more compact than relays, and are very common for switching 24VAC solenoids.

On Friday, January 18, 2013 10:58:42 AM UTC-5, pbor...@gmail.com wrote:

Hey everyone,

A group of friends and I are trying to build an automated sprinkler system with the BeagleBoard-Xm and we ran into a wall. We hoped you guys might have any advice.

Basically we wanted to use our board to control the siphon valve on the sprinkler system. That doesn't seem too hard, but the board cannot provide enough voltage to switch the valve on. We thought about using a switch or relay module that would basically allow the 24V or however much voltage we need to go to the valve. Would anyone know which relay module would best be suited for this? Or any other suggestions would be helpful as well!

Thanks!