Lifewater Canada

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Build Your Own Water Level and TDS Sensor

One of the challenges in drilling wells is finding the depth of the water, the water recovery rate and the quality of the water.  Normally, two measuring devices are used.  One, an Electric Water Level Tape, and the other, a TDS or Total Dissolved Solids Meter are used.  Both are very expensive instruments which use fragile electric meter movements to detect electric current.  The challenge facing those drilling wells in third world countries is to have something that does the same thing in an inexpensive rugged instrument.

One option is to build an astable multivibrator using a TLC555 timer.  This timer is ideal because of its extremely low power consumption.  The circuit can be built right into an older style telephone handset with all components (probe excepted) included in the handset.  The circuit works by sensing the resistance of the probe.  If the probe is open (not touching water) the circuit will produce an audio frequency around 400 hz.  When the probe touches quality water, the frequency doubles (approximately) increasing the tone by about one octave.  If the water has dissolved solids  in solution, the tone will quickly go higher giving the person measuring an approximation of the mineral quality of the water.  A fairly high note, nearing a squeal would indicate the detection of brine or extremely high levels of hardness etc.  If, for some reason the probe shorts, the circuit will produce a very high pitched whistle that will not change when the probe comes in contact with water.  Though this circuit does give a approximate estimate of the hardness of water, it will not give a good estimate of the SAFETY of the water.  For a further explanation of its limitations, please go to Frequently Asked Questions

(If you go to a picture, or diagram via a link or camera, just hit your Back Button to return to the place you came from.)

The circuit once attached will fit nicely under the speaker with the speaker unit in place.  A miniature momentary push button switch should be used between the 9V Alkaline battery and the circuit.  This ensures that the unit cannot accidentally be left in the on position.  The switch is best mounted near the ear speaker where it can be easily depressed by the thumb or index finger.  The battery can then be installed where the microphone and microphone socket were installed.

The probe wires can exit out of the original curly cord inlet.  Once the wires are installed, this hole should be sealed with silicone (Do NOT use Mono as a sealant since it has electrical properties that enable the flow of current which messes up the reliability of the circuit.)  The probe wire can be from 50' - 500'.  In our first model, we used standard 24 gauge speaker wire because of its flexibility, size and price.  100' of probe speaker wire can nicely be wrapped around a piece of wood siliconed to the back of the handset for easy storage and portability.  A round non porous rock, approximately 1" in diameter works well as a weight for the probe.  Using a little silicone and an elastic band will attach the wire to the rock.  Make sure that you do not cover the tinned wire ends with silicone.
Parts List
Northern Electric Style G3 Telephone Handset with ear and mouth covers
HHMR-80V(U-1) Receiver Unit,  Diode must be Removed (clip it off if necessary) 
Other possible part numbers (1182, ?)
1/4" Long Connecting Screws for the above Receiver.  These will be used to mount and connect the circuit board to the receiver unit.  If you have an older reciever unit, 1/4" screws will already be on the reciever.  If however you have a newer unit, 1/4" screws will have to be obtained since the included 1/8" screws are not long enough.
#12 lock washers to improve the connection between the receiver and prevent shorts on the foil side of the circuit board.
Momentary On Push Button Switch (i.e.. push to talk switch, the smaller the better)  The quality of this switch is essential since it is the one moving part in the entire unit.
100' (or more) 24 gauge multi-stranded or braided speaker wire (flexibility, size and durability are essential considerations)
Water Sensor Printed Circuit Board (make it if you have the resources, skills and equipment, or order it directly from us.   Mask information is included below if you choose to make your own circuit board)
TLC 555 Timer
10K Ohm Resistor (brown-black-orange) 1/4 or 1/8th watt
1K Ohm Resistor (brown-black-red) 1/4 watt
2.2K Ohm Resistor (red-red-red) 1/4 or 1/8th watt
.1uF capacitor
1 foot black stranded internal connecting wire
1 foot red stranded internal connecting wire
9V Battery Connector
9V Alkaline Battery
Tub and Tile Silicone Sealant
Wooden Wire holder shaped as pictured below made to fit the back side of the telephone hand set.
General Purpose Elastic Bands
Round Rock 1"

Step by Step Building Instructions

1. Printed Circuit Board Preparations
A.  Obtain the "Well Sensor Printed Circuit Board" and proceed to install the parts as shown in the graphic immediately below.  This view has the copper foil on the bottom side.  All parts should be installed right on the circuit board without extra lead length.  This encourages ruggedness. 
  1. Install the 1K Ohm Resistor (black-brown-red) tight against the circuit board in position R1. 
  2. Install the 2.2K Ohm Resistor (red-red-red) tight against the circuit board in position R2. 
  3. Install the 10K Ohm Resister (black-brown-orange) tight against the circuit board in position R3. 
  4. Install the TLC555 timer snugly on the top of the circuit board.  Make sure that Pin #1 is situated as marked below! Pin #1 is usually marked by a dimple on the printed circuit that cannot be worn off (like print).  Make sure that all 8 pins are protruding through the circuit board!  Bend two pins at opposite corners of the TLC555 to hold it in position until you solder it. 
  5. Install an insulated jumper wire as shown. 
  6. Install two .1uF Capacitor at C1 and CAdj 

B.  Turn the printed circuit board over, carefully place it in a small vice to keep it secure and solder the components onto the board.  Because of the size of this circuit, it is recommended that a person with electronics experience do this task. Overheating can damage the circuit board or its components.  Under heating can cause the solder to bead and make a poor connection.  Quality soldering equipment makes a world of difference!  A site that shows and teaches you how to solder is Once the parts have been properly soldered in position, clip off any excess lead length, as close to the circuit board as possible without clipping the actual soldering itself.  Clipping the soldering can break the solder bond between the lead and the foil.  Leaving the leads too long will cause the unit to short once it is mounted on the back of the receiver.

R1 = 1000 Ohms               C1 = .1uF
R2 = 2200 Ohms           C2 = ~.1uF
R3 = 10K Ohms

Your Circuit board should look like this once the parts have been soldered in place. 
2.  Handset Preparations
  1. Remove microphone, microphone socket, curly cord and wires from the G3 Telephone Handset.  Retain the receiver (speaker) as it will be used in the set.  If you have not already done so, REMOVE THE DIODE FROM THE BACK TERMINALS OF THE RECEIVER (SPEAKER).
  2. Drill a 5/16" hole in the neck of the handset near the ear piece as shown below.
  3. Take the Miniature Momentary On Push Button Switch and connect a 3" stranded RED wire to one terminal and a 9" stranded RED wire to the other terminal.  Make sure that these connections are properly soldered. 
  4. Place the 3" wire through the Vdd terminal on the circuit board from the top side.  Solder the wire in place. 
  5. Connect a 12" BLACK stranded wire to the GROUND terminal of the Well Sensor Circuit Board, soldering it in place. 
  6. Take the Telephone handset and insert the probe wire into the original curly cord hole near the mouth piece.  Slide the wire through the handset to the Receiver compartment.  Run a little extra through so that you will be able to attach it to the circuit board with ease. 
  7. Strip 1/4" off of the end of each of the probe wires, twist and tin them.  Insert them in the above probe connection locations, solder in place, clip off ANY excess wire on the foil side of the circuit board. 
3.  Attach the circuit board to the receiver.
  1. Insert the two #12 X 1/4" screws through the circuit board from the component side. (They should fit through the holes snugly). 
  2. On the foil side of the circuit board, with the screws protruding, place 2 lock washers on each screw.  These lock washers will ensure a connection to the receiver and offset the circuit board so that the soldered copper foils will not short on the back side or metal portions of the receiver.
  3. Mount the circuit board on the receiver. . Tighten the screws so that they are just snug and the lock washers have been compressed.  This will ensure a continuous and secure connection. 
4.  Putting the Handset Together
  1.  Mount the Push Button Switch in the 5/16" hole making sure that the RED 9" stranded wire proceeds through the handset to the battery compartment (mouth area) of the unit. 
  2. String the BLACK 12" stranded wire through the handset so that it also protrudes from the battery compartment. 
  3. Attach the 9 Volt Battery connector - Red wire to red wire, Black wire to black wire.  Solder the connections and cover them with a dollop of silicone.  Let the silicone dry. 
  4. Attach the battery taking note to make sure you are attaching it with correct polarity.  This circuit is not protected against those who try to put on batteries backwards while pushing the power button! 
  5. Once the battery is installed, push the power button.  You should hear a frequency that would compare to a middle "C" on a piano.  If you hear this sound - Congratulations - you have passed test #1. 
  6. Double check your connections. 
  7. Carefully insert the 9 Volt battery in the mouth side of the Telephone handset aiming the end of the battery down the throat of the handset.  It should "just fit!"  If it is a little tight, you might choose to scrape a little out of the opening edges of the throat of the handset with a sharpe knife.  DO NOT CUT THE WIRES BY ACCIDENT!  Newer handsets should easily have enough room.  Once the battery is in place, screw on the microphone/battery cover. 
  8. Carefully guide any excess wire into the ear section of the Telephone handset as you insert the Receiver with the circuit board mounted on its back side.  The receiver should fit flush with the edge of the handset opening.  If you find it does not want to fit, take it out again.  You may be pinching a wire if you force it into place.  If it fits properly, place the ear cover over the receiver.  Once again, push the power button, you should hear the same frequency.  If you hear the same sound - Congratulations - you have passed test #2. 
5.  Preparing the probe.
  1. At the end of your probe wire (100' or more), strip off 1/2" and tin the wires with solder.  This will give the copper some protection from corrosion (salt water corrodes almost everything). 
  2. Take a permanent marker (Sharpie Permanent Markers work very well for this.)  Starting from the tinned end of the probe, mark with a black marker at 1' increments the entire length of wire.  Once this is done, go back to the tinned end, and then with a red maker, add a blue line at every ten foot increment, with an extra line or each additional 10' increment. In between, at 5', 15', 25' 35' 45' 55' etc... place a line with red marker to indicate the 5s on the wire.  This will help to measure the depth of the sensed water. 

The probe can be weighted with a 1 inch marble or even a simple non porous rock, tied between the leads with an elastic band or siliconed between the leads.  If you happen to loose the rock, replacements should not be hard to come by! 

6.  Preparing the Probe Storage Block
Put your well water sensor to the side.  Find a piece of wood approximately 1" wide.  If you use lighter wood, it is easier to cut and shipping costs less!   Cut it to the shape shown below. You may want to use the template provided below.  Print it out, it should print out to the right dimensions.  Once you have cut it out, sanded and or finished it to your pleasure, silicon it to the back of the handset.  Let the silicone cure. Once the storage block is secure, carefully wrap the well water probe wire around it.   Want to Print out the block we made to scale - Click here to Go to WoodBlock  Diagram
7.  Test your Well Water Sensor
  1. Pressing the power button should produce approximately a "middle C." 
  2. While pressing the power button, dip the probe in pure water, the tone should go up about 1 octave. 
  3. Start adding a little salt to your sample of water and stir the water slightly.  Notice how quickly the unit detects salt in solution. 
8.  Calibrate Your Probe
The advantage of using musical tones for the purpose sensing water and water quality is that musical tones are understood throughout the world.  This Well Water and TDS sensor can be relatively calibrated very simply.  The procedure for calibration is follows: 
  1. Find a pure sample of water.  This need not be distilled H2O, it should be, however water that would be regarded as high quality by Hydrology standards. 
  2. Make sure you have your rock or other non - metallic weight permanently attached to your probe wires. 
  3. Depress the activator button and slowly dip your probe into quality water.  The tone should progressively go up about 1 octave.  If it does not quite go up an octave, you either are using extremely low TDS water, or your exposed probe length is not long enough.  Feel free to strip a little more insulation off of the probe wires and re-tin the exposed strands.  Go back to step #2. 
  4. If you the tone goes up more than an octave, you can trim the length of the exposed probe lead with a scissors in small increments.  Repeat this procedure until you have achieved a tonal change of one octave. 
  5. Now for the sake of coming to know how to measure TDS, add a measured amount of salt to the water, record the number of notes, in excess of 1 octave that the tone increases. 
The Well Water Sensor Circuit Board
This circuit board is designed to be mounted directly to the back of a standard telephone speaker (with the original diode removed).  The exact distance from center to center of the mounting holes should be 15/16".  Accurately scaled 1-1 and 2-1 positive and negative foil photo masks are linked below.  When mounted on the back of the speaker, the foil side of the circuit board should be toward the speaker for purposes of contact with the speaker contacts.  Lock washers should be between the circuit board and the speaker contact to provide spacing and better contact. 
Foil Side of Circuit Board Drawn to Scale

Under this color diagram are links to accurately scaled 1-1 and 2-1 positive and negative foil photo masks that should print out in exact dimensions.

Some Pictures of the actual Well Water Level Sensor
This is the view of the constructed Well Water Level Sensor.  The Rock would normally be attached with an elastic band and some silicone. 

The 1 inch thick wooden block on the back of the handset nicely holds about 100 Feet of #24 guage speaker wire.  If you silicone it to the back of the handle, the connection should be quite durable. 

An exploded view of the Well Water Level Sensor from the side. 

This exploded view shows the momentary push button switch location.  Here the circuit board has been removed from the receiver. (Back).

A view of the circuit board attached to the receiver. (Back)

A view of the foil side of the circuit board and the receiver.  Notice that the diode has been removed from the back side of the receiver.  The 1/4 inch screws should fit snuggly through the circuit board.  Notice the two lock washers on one of the screws in this picture.  These lock washers should be placed on both screws before mounting on the back of the receiver. 

The circuit board mounted on the back of the receiver.  Notice that the capacitors or positioned to take a minimum of vertical height as there is little room in the receiver compartment once the unit is put together.  Look closely and you will see the two lock washers separating the circuit board from the receiver. (Back)

The battery fits nicely in the throat of the hand unit. 

Circuit Diagram and Technical Details
"The TLC555 is a monolithic timing circuit fabricated using the Lin-CMOS* process.  Due to its high impedance inputs (typically 1012 Ohms), it is capable of producing accurate time delays and oscillations while using less expensive, smaller timing capacitors then the NE555.  Like the NE555, the TLC555 achieves both mono stable (using one resistor and one capacitor and astable (using two resistors and one capacitor) operation.  In addition, 50% duty cycle astable operation is possible using only a single resistor and one capacitor.  It operates at frequencies up to 2 Mhz and is fully compatible with CMOS, TTL, and MOS logic.  It also provides very low power consumption (typically 1 mW at VDD = 5V) over a wide range of supply voltages ranging from 2 volts to 18 volts.

Like the NE555, the threshold and trigger levels are normally two thirds and one third respectively of VDD.  These levels can be altered by use of the control voltage terminal.  When the trigger input falls below trigger level, the flip-flop is set and the output goes high.  If the trigger input is above the trigger level and the threshold input is above the threshold level, the flip-flop is reset and the output is low.  The reset input can override all other inputs and can be used to initiate a new timing cycle.  When the reset input goes low, the flip-flop is reset and the output goes low.  Whenever the output is low, a low impedance path is provided between the discharge terminal and ground.

While the complementary CMOS output is capable of sinking over 100mA and sourcing over 10 mA, the TLC555 exhibits greatly reduced supply current spikes during output transitions.  This minimizes the need for the large decoupling capacitors required by the NE555."

(Quoted from the TLC555 Technical Data supplied by Radio Shack, Catalog #276-1718)

Template for wooden block
Frequently Asked Questions:

Have Questions About this Unit - Email Me, I'll try answer them.

1.   Does this sensor detect the quality of water so that I can tell it is Safe to Drink?
Response:  The sensor's qualitative measure of Total Dissolved Solids (TDS) is a side bonus that has nothing to do with the safety of the water.  TDS measures the presence of minerals such as calcium & magnesium (which determine the hardness of water), sulphate, chloride and alkalinity.  Lifewater teaches and practices the use of pathoscreen (bacteria) and nitrate tests to routinely determine whether or not water is safe to drink.  The qualitative TDS capability of the electric water level tape will be usefull when drilling near the ocean since it will give a rough indication whether or not high salt may be present in the water.  This will help drillers decide whether to spend extra money and complete the well, or whether a certain water bearing vein needs to be blocked off etc.  The presence of sodium chloride (salt) does not make the water unsafe to drink, but can give it an unpleasant taste and cause premature corrosion of certain pump parts.