Rain Detector Electronic Circuit Diagram

Rain Detector Electronic Circuit Diagram

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On: 13 Jun, 2016

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Category: Alarm

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How to build Rain Detector

This rain detector will give you a heads-up the instant it starts to rain, hopefully giving you time to close windows and bring in possessions. The battery-powered circuit draws virtually no curr...

How to build Rain Detector

This rain detector will give you a heads-up the instant it starts to rain, hopefully giving you time to close windows and bring in possessions. The battery-powered circuit draws virtually no current when the sensor is dry and the current consumption is low when the buzzer is activated so a couple of AA cells will last a long time. Alternately, a molded power supply with a simple voltage regulator to drop the voltage to 3 volts could be used. The circuit is basically a handy flasher circuit that operates well on only 3 volts using ordinary silicon transistors. When the circuit is triggered, the buzzer is pulsed about once per second for a very short time, giving it a "dripping water" sound which seems appropriate. A slower, longer beep may be had by increasing the 1 uF capacitor. The 10 k resistor may be increased for a longer beep time without decreasing the beep rate but at some point the circuit will cease to function properly, depending on the gain of the transistors.

rain detector 1.gif

Parts Considerations:

Just about any transistors will work but if you choose to use older, low gain transistors in metal cans just because they are so good looking (like I did), it might be best to try a 4.7 k and 2.2 uF in place of the 10 k and 1 uF. (I had no trouble with a 2N2222 and 2N2906 with the values shown but those are modern types.)


The resistors are not critical at all and any type or size should work fine and reasonable close values are OK although the values shown are quite common.


The 1uF capacitor may be just about any type, with a 16 volt aluminum electrolytic being the most likely choice. The capacitor will see about 1/2 volt reverse bias at times so a 10 volt or higher tantalum capacitor is a better choice; they can handle about 10% of their rating in reverse. A non-polar ceramic capacitor is also a good choice but don't hesitate to use a cheap electrolytic since there is a large resistor in series limiting the reverse current and this isn't exactly a deep space probe!


The 0.1uF is not critical at all and my circuit works just fine without it. It is there in case the buzzer's noise tended to retrigger the circuit.
The switch is any single-pole, single-throw type. My switch, grabbed from the surplus bin, has an unnecessary spring-loaded momentary position, too. I wired it to supply power to the circuit in both positions with the idea that the "test" position is for determining if the sensor has dried sufficiently to turn the circuit back on. Just an excuse to use the switch!


The batteries are just AA alkaline cells with wires directly soldered to the ends for connections. Directly soldering to a battery is a delicate process and I recommend a battery holder for the less experienced solderer. You must make the joint very quickly or the battery will be damaged! Don't dwell on it!
The buzzer is a 1.5 to 3 volt, 15 mA "mini buzzer" purchased at Radio Shack.
The copper-plated nails are available at most hardware stores. Mine are 1.4 mm x 19 mm (3/4").

The circuit is built on perforated circuit board and mounted in a little plastic box:

rain detector 2.jpg

Neither the construction or the components are critical but I do recommend a connector for the sensor to make it easy to work on the box. I used an ordinary 1/8" earphone style connector.

The rain sensor may be built any number of ways and is simply two conductors that are bridged by the rain water. A simple sensor is shown below. Two conductors of bare copper wire are woven through the holes so that the conductors are near each other but do not come into contact. Notice the holes each conductor uses are staggered so the loops underneath miss each other. Ordinary phone cable is used to connect to the electronics.

rain detector 3.jpg

The sensor above will last a reasonable length of time but a more permanent design is shown below:

rain detector 4.jpg

rain detector 5.jpg

This probe will cost at least 6 cents! It consists of a penny and nickel sandwiched together with a plastic insulator in the middle. Rain drops bridge the gap between the coins, triggering the circuit. The unit is quite weatherproof and should last for years. Here's how to make it:

First, drill a small hole in the center of a penny just big enough for a copper plated nail to pass through. Solder the head of the nail to the penny with a complete fillet to seal out the rain. Now find a fairly thin sheet of plastic slightly bigger than the penny. Possible sources include the lid from a drink bottle or a lid from a peanut jar. I used a flat section of plastic from a bubble packaged product. (My particular choice was quite thin and the sensor takes a long time to dry out. ) Coat the plastic with spray adhesive and push the nail through, gluing the plastic to the underside of the penny. Once the glue has dried, use scissors to carefully trim the plastic flush with the penny. The goal is to form an insulating washer the exact size of the penny. Now drill a larger hole in the center of a nickel, perhaps 1/4". Wrap the nail with tape to mask it and spray the exposed face of the plastic washer with glue. Stick the nail through the nickel to make a penny, washer, nickel sandwich. Position the penny right in the center of the nickel and let the glue dry.

rain detector 6.jpg

Once the glue has dried, remove the masking tape from the nail and fill the gap between the nail and the nickel with epoxy. Cut the nail short with a pair of old cutters or the cutter on a pair of pliers (not your best electronic wire cutters) since the core of the nail is steel. To avoid stress on the epoxy, don't hold the nickel as you cut the nail; hold your hand below and catch it as it falls. Solder one conductors of a length of phone wire to the nail and the other to the nickel as shown in the photo. Do not solder the wire to the nickel close to the edge as I did in the photo; that wire had to be moved in toward the center to prevent interference with the housing. Cut an arbitrary length of 1/2" PVC electrical conduit to form the housing; three or four inches is fine. Make sure one end is perfectly flat and straight. Coat that end of the pipe with epoxy and feed the wire through to glue the nickel in position. Once that has cured, turn the assembly over and pour a tablespoon or two of epoxy into the tube to get a really good seal. I decided to shove a few shipping peanuts into the hole to form a plug and poured in more epoxy to get a flush seal so that insects can't build a nest inside and surprise me later. Lead the wire inside the house to the electronics, leaving a hanging loop near the entry point to prevent water from following the wire inside, add a connector and that's it. This probe should be quite weatherproof but it may need an occasional cleaning if debris collects between the edges of the coins.

For historical purposes, I include my old design below. The circuit will run the batteries dead if it rains while you are away so a molded power supply is a better choice. For connection to a computer, I recommend replacing the beeper with an optoisolator to protect the computer. The LED in the optoisolator would be connected in series with an appropriate resistor, perhaps 470 ohms and the output transistor of the optoisolator would be connected to a suitable input port with a pull-up resistor to the computer's 5 volt supply. The simple serial port interface might be an interesting starting point. With a similar basic program one pin could be set to provide the voltage for the optoisolator and another pin could read the status.

It may sound silly at first. After all, how hard is it to look outside to see if it is raining. But if you start to pay attention, you will be surprised how often you miss the start of a rain storm. With this simple rain detector, the first few drops of rain will sound the alarm allowing you a few precious seconds to roll up windows and bring in possessions. When used as part of a computer weather data collection system, the exact time of a shower may be recorded. Fig.1 shows a simple rain detector consisting of two strips of aluminum foil glued to a piece of plastic. A single square of foil is glued to the plastic with two lead wires underneath as shown in the figure. The lead wires are striped back so that the foil makes good electrical contact with the conductors but the bare wire should not protrude so that the foil will protect the wire from corrosion.

rain detector 7.gif

A narrow zig-zag gap is cut in the foil to electrically separate the two lead wires. The rain drops bridge the gap causing conduction which is sensed by the circuit shown in fig. 2.

=========================================================================

How to Make a Rain Detector Circuit

Introduction:

Rain detector circuit is the device which will really work as you wish what you want to do. It is a device which will generate the signal when the rain comes. The frequency will be more when the rain is heavier and the frequency is very less when the rain will be low. It all means that the frequency will depend upon the rain. We always should focus upon the signal making. Don’t focus on the rest of the part which we have to make it. When we get the signal now we can do anything we want to do.

We will make a single wire circuit so that the circuit is easy and every reader can read it. Double wired is quiet complicated and the circuit which is made has to be with a IC’s so I will prefer today to show you with single cable and for complicated circuit you may go to article how to make a rain detector with IC’s.

1st experiment:

As you know that not a single machine is made with having all facilities in first attempt so here it go.

This is the easiest circuit that you have ever seen. In the practical of school, this is done in 5th or 6th class. It is very easy to make and only few cheapest thing is required.

Aim: To make rain detector.

Material required:

                LED, connecting wire, battery and a zigzag switch like in calculator.

Procedure:

  1. Connect everything as you can. I hope that you can glow the led by connecting the wire. And you will not see in the pitcher for help you can see this picture.

how to make a rain detector circuit 1.jpg

     2. Prepare rain detector probe. For that only connect the wire on the two end of the switch.

how to make a rain detector circuit 2.jpg

  1.  Connect wire of that length so that the detector reaches your roof.
  2.   Cut the wire of the led circuit from anywhere.

how to make a rain detector circuit 3.jpg

     5. Connect the detector in the terminals of the led circuit.

how to make a rain detector circuit 4.jpg

  1. Now when the rain will come or the detector pad become wet by any source then the circuit will glow

 We have made a circuit that will work according to the rain. But there are lot of disadvantage on this circuit.

Advantages:

  1.        It is very cheap.
  2.       The battery last very much.
  3.       Not risky.
  4.       No harmful effect.
  5.      The circuit can be made by everyone.

 

Disadvantages:

  1. It doesn’t tell about the speed of the rain which is fallen on the roof.
  2. It will send signal or the led will be glowing until the detector becomes wet.
  3. It something is over that then the detector will not work until it gets wet.
  4. There are so many problem that you will face when you will make this circuit.

To minimise the disadvantageous we have made some changes that will be in experiment 2.

Enhanced Circuit

2nd experiment:

This is the modified experiment that in this the only the change is in the detective plate.

Aim: To make good rain detector.

Material required:

                LED, connecting wire, grills and battery.

Procedure:

  1. Connect everything as you can. I hope that you can glow the led by connecting the wire. And you will not see in the pitcher for help you can see this picture.

how to make a rain detector circuit 5.jpg

     8. Prepare rain detector probe. For that only connect the wire on the two end of the switch.

how to make a rain detector circuit 6.jpg

  1. Connect wire of that length so that the detector reaches your roof.
  2. Cut the wire of the led circuit from anywhere.

how to make a rain detector circuit 7.jpg

    11. Connect the detector in the terminals of the led circuit.

how to make a rain detector circuit 8.jpg

  1. Now when the rain will come or the detector pad become wet by any source then the circuit will glow

 We have made a circuit that will work according to the rain. But there are lot of disadvantage on this circuit.

Advantage:

  1.         It is very cheap.
  2.        The battery last very much.
  3.        Not risky.
  4.      No harmful effect.
  5.       The circuit can be made by everyone.
  6.       It doesn’t tell about the speed of the rain which is fallen on the roof.

 

Disadvantages:

  1.         It doesn’t tell how much does the rain have at a given time.
  2.       It doesn’t tell the rain timing.
  3.       It doesn’t tell many more details require.

 

Creating signals:

Now for signal only thing you have to do is add transistor as shown in diagram.

how to make a rain detector circuit 9.jpg

====================================================================

Rain detector usage with TCW220

In this article will be shown how to use Ethernet data logger TCW220 with a rain detector.

Two different rain detectors are used – RG-11 and CON-REGME. RG-11 is manufactured by Hydreon Corporation, while CON-REGME is manufactured by B+B Thermo-Technik.

1. Test setting

An example test setting is shown in Fig. 1. Both rain detectors are powered by the controller TCW220.

rain detector usage with tcw220 1.jpg

In the event of rain or snow, they send a signal to the digital inputs of Ethernet data logger TCW220 (the rain detector RG-11 to digital input 1, the rain detector CON-REGME to digital input 2). The controller TCW220 is equipped with a logger which enables the storage and comparison of the information received by the two rain detectors.

Fig. 1

The corresponding connections between the controller and the rain detectors are shown in Table 1.

rain detector usage with tcw220 2.jpg

To get accurate measurements from the rain detectors, they have to be mounted in a spot where there is free access to rain.

rain detector usage with tcw220 3.jpg

A mandatory requirement when assembling the rain detectors is all components to be dry because any moisture in them creates condensation which may damage the rain detector.

2. Principle of operation of rain detector CON-REGME

This type of rain detector uses a sensor that detects the conductivity changes on the sensor surface. That change leads to the activation of a relay which then sends a signal to the digital input of the controller TCW220.

This rain detector operates at different sensitivity levels which can be changed so that the presence of fog can also be detected. The sensor surface can be heated which will enable operation at low temperatures and will speed up the drying process of the sensor.

rain detector usage with tcw220 4.jpg

3. Principle of operation of rain detector RG-11

This type of rain detector uses infrared rays that are reflected by a lens. When there is water on the lens, some of the rays get reflected.

The sensor detects the difference in the intensity of the rays and then activates a relay which sends a signal to the digital input of the controller TCW220.

These rain detectors can operate at different sensitivity levels and in various modes that are changed by using DIP switches.

rain detector usage with tcw220 5.jpg

4. Test results

Figure 2 shows the feature of the controller TCW220 to display the saved data from the rain detectors and to compare them.

In the case below, the rain detector CON-REGME, using a sensor for changes in the conductivity, is the first to detect the presence of rain in both measurements. The detector using infrared rays has registered it later because depending on its operating mode, it will send a signal for the presence of rain at the specific intensity of the rain.

A signal that it is not raining is first sent by the rain detector RG-11, and later by CON-REGME whose surface dries up a little more slowly.

rain detector usage with tcw220 6.jpg

5. Conclusion

Each of the tested sensors in combination with Ethernet data logger TCW220 can be used for condensation sensing, irrigation control, automation of greenhouses, balcony sun shades, and so on.

 

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