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DanS
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« on: July 07, 2012, 10:13:37 AM » |
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I just finished constructing a rain sensor a that's a little different. It's wireless (using the wireless doorbell again) and used a "single pulse" front end design to avoid the constant alarm while it's raining. That is, it rings once when it first detects rain then silences until the sensor grid dries and resets for the next shower. I needed something to alert when it's time to bring in the laundry.  The attached photo's show how the actual sensor grid was made. 2 cut sheets of common aluminum window screen with a thin (as you can get) plastic separator (basket net fruit bag works great). Items required, couple electronic components, weatherproof case, cabling. The sensor finished and ready. Schematic if someone wants to build one. |
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« Last Edit: August 03, 2012, 02:00:53 AM by DanS »
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sam2004gp
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« Reply #1 on: July 07, 2012, 10:28:10 AM » |
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Looks good!
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DanS
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« Reply #2 on: July 07, 2012, 08:34:33 PM » |
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Thanks Sam. Heading off to church this AM but afterwards I'll put it up. Forecast is scattered showers for this afternoon so with any luck it will see it's "first water" today.  |
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Cienega32
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« Reply #3 on: July 08, 2012, 03:45:59 AM » |
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Pretty neat! How many drops did it take to trigger?
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DanS
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« Reply #4 on: July 08, 2012, 04:05:43 AM » |
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Pretty neat! How many drops did it take to trigger?
The first drop of several does it. I used a drinking straw filled about 1/4 inch and when I release the water over the grid the first drop would set it off. The values of the components in the pulse section of the circuit keep the sensor quiet after the first trigger (drop) until the gap between the 2 screens clears (dries) then it's ready again. |
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« Last Edit: July 08, 2012, 04:28:41 AM by DanS »
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W3DRM
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« Reply #5 on: July 08, 2012, 03:27:30 PM » |
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Not to be negative on this but, I am wondering how this will work over a long period of time? Seems to me that when a drop of water evaporates it will leave behind some bit of residue which over time may build up and either cause a short-circuit or reduce the sensitivity of the device. Of course you could just build a new one and start all over again...
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Don - W3DRM - Minden, Nevada --- Davis Wireless VP2, VWS 14.00 p101, StartWatch, VirtualVP, VPLive, WL 5.9.3, Win7 Ultimate-SP1 --- Logitech QuickCam Fusion webcam  |
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DanS
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« Reply #6 on: July 08, 2012, 07:08:06 PM » |
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That's something I should keep in mind and check for from time to time. I guess if/when something like that occurs I could try a high(er) pressure hose to spray it out.
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ed2kayak
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« Reply #7 on: July 08, 2012, 09:34:33 PM » |
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Cool project, thanks for sharing.
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Ed CoCoRaHS PA-CD-6, Weather Underground KPAMECHA7, CWOP DW5425  |
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W3DRM
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« Reply #8 on: July 09, 2012, 12:49:05 AM » |
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Dan,
Do you get false hits with the sensor? If so, here is something to watch for...
I used to live in Hawaii and at the Univ of Hawaii in Hilo one of the professors there in charge of their rain fall studies division had a devil of a time trying to figure out why his sensor (not too unlike yours) would intermittently trigger when there was no rain or moisture on the sensor. After many months of watching the sensor (it was in the middle of the rain forest outside of Hilo), he finally discovered the false triggers were caused by a spider walking over the sensor. I wonder how many thousands of taxpayers dollars went into that study and what good really came out of it? The primary purpose of the study was to see what the impact rain drops had on the foliage and soil in the rain forest. I was the tech over there who serviced their computers back in the 70's. It was a great assignment, I must admit.
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Don - W3DRM - Minden, Nevada --- Davis Wireless VP2, VWS 14.00 p101, StartWatch, VirtualVP, VPLive, WL 5.9.3, Win7 Ultimate-SP1 --- Logitech QuickCam Fusion webcam |
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DanS
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« Reply #9 on: July 09, 2012, 01:23:15 AM » |
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Hi Don. I really haven't had mine out long enough but so far no false hits (yet?). I'm also using 2-conductor shielded cable from the sensor grid to the circuitry thinking it could pick up strays on the line. I have learned that the distance between the sensor screens determines the droplet size required to trigger it. I started with approx. 1/16" gap and a regular eye dropper size droplet will set it off every time. However, I found out yesterday that a light sprinkling rain must have smaller drops and it took a minute or two to trigger. Kind of defeats to whole purpose of what I trying to do here. Today I'm building a different, much thinner gapped sensor screen to see how that works. Thanks for the heads up with the spiders (we have lots of little lizards too) setting them off.
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« Last Edit: July 11, 2012, 03:39:22 AM by DanS »
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DanS
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« Reply #10 on: August 10, 2012, 12:08:35 AM » |
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revision C to the grid portion. I've found a more sensitive configuration for the actual drop detector portion of this. 2 stainless floor drain grills separated by the plastic netting mentioned above. The grills are rotated so the holes are staggered in relation to each other so the drops can contact both layers. This arrangement is a lot more sensitive and quick to respond to even the lightest rains compared to the screen layers and an alternating etched circuit trace design. The 2 grills can't be soldered to with conventional methods so I just snipped and drilled small tabs and screwed terminals to them for the wire connections.  Here's a pic with a hanger head attachment.  |
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sam2004gp
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« Reply #11 on: August 11, 2012, 03:21:54 PM » |
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Very Ingenious.
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