Hello,

We are looking for a way to apply water to plants on trailers. We envision a break beam sensor that triggers a 30 second timer. That should be enough time to drive under the watering device. The valves that we use are 24VAC. I see 24VAC sensors and timers, but no clear information about how to wire and set up. Maybe the device already exists, I just don't know what to search for?

Suggestions?

Thank you.

 

The Mechanics of what You need to accomplish are more demanding than
the simple Circuitry required to operate the (existing ??) Solenoids.

Pictures would do wonders.

You may not need a "Timer" at all.

Are You pulling a Trailer underneath an overhead framework of Water-Nozzles ??

Are You "backing-in", or "driving-through" ??
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Sorry for the lack of detail. It has not been constructed yet. Yes, the concept is for a tractor to pull a series of two or three trailers through an overhead framework with water nozzles suspended from the framework. The idea being that the tractor breaks the beam and triggers the water flow.

It hadn't occurred to me to consider modifications that would eliminate the timer. That's brilliant.

If I do that, how do I use a break beam sensor to trigger the solenoid on the water valve?

Thinking of this Seco-Larm product. The Pdf shows two wires to power the sensor and a pair for the switch. I assume that I will need to run four wires total. Two just to power the sensor, then another pair, with one running directly to the solenoid and one running up to the switch and back to the other side of the solenoid.

 

It would seem that you've answered your own question.
Now it comes down to logistics.
Is it OK to spray Water on the Tow Vehicle ?
Would an "On-Delay", of lets say ~20-Seconds, be advantageous ?
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I assume that I will need to run four wires total.

Technically it can be done with 3 wires. The specs indicate the unit can be powered with 12 to 30 VDC or AC. However the contacts are only rated at 2 amps so not sure if that will work depending on the number of valves and the current draw.
Below is a wiring diagram using a 3 wire hookup.

 

Remote control switch operated by the driver, and then optional timer unit to stop the water if driver forgets to turn it off, you find them extremely cheap from China.
4 channel remote:

https://www.aliexpress.com/item/100...#3564#16062#353&pdp_ext_f={"sceneId":"23416"}

 

Tow rig can get wet, I figured we'd put the sensor out ahead of the nozzles so that they would start before the trailer gets to them. Don't think a delay would be necessary.

To complicate things there are two possible tow rigs of different sizes and there is a four foot gap between trailers. So I need to figure out how to keep the water running as the gap reaches the sensor between the first two trailers so that the rest of the second trailer and then third or fourth trailer get watered. This is where I was thinking a timer might be a solution.

Would some kind of multiple sensor system be appropriate?

For example sensor A and Sensor B would be maybe 5 feet apart. The tow rigs is vary from 6 feet to ten feet long. All trailers are 10 feet long plus a 4 foot tongue.

The tow rig reaches sensor B first which turns on the water. The tow rig reaches sensor A before Sensor B sees the gap between the rig and trailer 1.

I imagine somehow the circuit turning on the water if either or both sensors are blocked. Perhaps this is not possible or there is a simpler way.

 

2, or even 3 Sensors would be easy to wire in series,
but there may be a better way,
simply place the Sensor, and its Target-Reflector at an angle to vehicle travel.
~45 degrees should handle any gaps.
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Thank you so much. Can't wait to try it out.