This softener generates a sweeping frequency from 2 to 20 KHz. It may give better results in some hard water. The 220uH coil drives the coil on the pipe with a current of about 0.5A, this allows high efficiency with less heat and less cost of running.
Power supply has to be regulated 5V that can source 200mA.
The 8 pins PDIP buffers is a mosfet driver. IC's that can be used are: TC4420, MCP1406, MAX4420. These are very similar and pins are identical.

• The power to the PIC is regulated 5 VDC.
• The 8 pins PDIP buffer, 4420 is a 6 amp mosfet driver. IC's that can be used are: TC4420, MCP1406, MAX4420. These are very similar and pins are identical.
• 220uH coil can be any type for 0.5A current.
• The coil on the water pipe is made of 5 meter long insulated wire of 24 to 20 gage. The wire is turned around the copper or plastic water pipe (it can not be steel pipe) in a single layer. On a pipe of 20mm diameter it will form 55 turns. Since the wire is 5 meter long the number of turns will be different for different pipe diameter.
• The LED indicates current through the coil.

This softener generates a sweeping frequency from 400Hz to 5 KHz. It may give better results in some hard water. The output of the Arduino Uno or Nano is 64KHz and 32KHz for ATTINY85/45/25/13/13A. Pulse Width Modulated to the sweep of 400Hz to 5 KHz, the 220uH / 470uH coil blocks the high frequency and drives the coil on the pipe with a current of about 1A, this allows high efficiency with less heat and less cost of running.
ATtiny can be programmed using Arduino IDE and Arduino as ISP, see Technical Tips Burning bootloader with setting "Clock Source 8MHz internal", this makes the CPU working at frequency of 8MHz.
ATTINY13/13A is programmed using Arduino IDE and Arduino as ISP. Use these instructions https://www.electronics-lab.com/project/how-to-program-attiny13attiny13a-using-arduino-ide/ with the setting : 9.6MHz, no millis no tone, LTO enabled.
Power supply to the Arduino Uno or Nano is 7V to 10V , 100mA or higher. Power supply to the ATTINY85 is 5V 100mA or higher.
The 8 pins PDIP buffers is a mosfet driver. IC's that can be used are: TC4420, MCP1406, MAX4420. These are very similar and pins are identical.

• The power to the arduino is 7-10 VDC. When Arduino Nano is used connect the power supply to GRD (-) and Vin (+).
• The 8 pins PDIP buffer, 4420 is a 6 amp mosfet driver. IC's that can be used are: TC4420, MCP1406, MAX4420. These are very similar and pins are identical.
• 220uH/470uH coil can be any type for 1A current.
• The coil on the water pipe is made of 5 meter long insulated wire of 24 to 20 gage. The wire is turned around the copper or plastic water pipe (it can not be steel pipe) in a single layer. On a pipe of 20mm diameter it will form 55 turns. Since the wire is 5 meter long the number of turns will be different for different pipe diameter.
• The LED indicates current through the coil.

The electronic water descaler is more effective device than powerful magnets placed around the incoming mains water pipe. This device operates by wrapping coil of wire around the incoming water mains to pass a magnetic field through the water. The theory is that it causes the calcium in the water to stay in solution and so inhibit it from adhering to pipes, taps, baths and kettles.
Reading many sources about the way it works I decided to try and make one. A few days after installing it I noticed a difference in the behaviour of the deposit of lime scale in the kettle and around the sink, it was much easier to remove the deposit, also the scale deposit was reduced to about half the amount.
Since it's unknown the true benefits of lime to our health and we also don't know the effect of the residual magnetic in the lime, it is recommended to use the descaler for washing water only.

There are 2 version for the circuit, both have similar characteristics. Select the one that will be easier for you to get the components.

• The +V is 8 to 10VDC. The current at 10V is 50mA. Any 9V universal power supply is powerful enough. Make sure the voltage does not exceeds 15V because it can damage the 555 timer IC.
• The coil on the water pipe is made of 5 meter long insulated wire of 24 to 20 gage. The wire is turned around the copper or plastic water pipe (it can not be steel pipe) in a single layer. On a pipe of 20mm diameter it will form 55 turns. Since the wire is 5 meter long the number of turns will be different for different pipe diameter.
• The circuit is a 12KHz oscillator with a coil of 470uH at the output to limit the current through the water pipe coil to 300mA peak.
• 56K resistor and 1nF (1000pF) capacitor determent the frequency.
• You can use equivalents for BC337 and BC327.
• 555 timer has to be bipolar (555N) .
• 470uH can be any type that can carry 300mA.
• 1N4148, 680 ohm and LED are optional components to indicate output signal and coil are present.
• All resistors are 1/4 watt, 5% .

• The +V is 8 to 10VDC. The current at 10V is 50mA. Any 9V universal power supply is powerful enough. Make sure the voltage does not exceeds 15V because it can damage the 4049B CMOS.
• The coil on the water pipe is made of 5 meter long insulated wire of 24 to 20 gage. The wire is turned around the copper or plastic water pipe (it can not be steel pipe) in a single layer. On a pipe of 20mm diameter it will form 55 turns. Since the wire is 5 meter long the number of turns will be different for different pipe diameter.
• The circuit is a 12KHz oscillator with a coil of 470uH at the output to limit the current through the water pipe coil to 300mA peak.
• 33K resistor and 1000pF capacitor determent the frequency.
• 4049B is a 4000 series CMOS. Any make is ok.
• 47nF cap. and 1K resistor are noise suppression, they can be omitted.
• You can use equivalents for BC337 and BC327.
• 470uH can be any type that can carry 300mA.
• 1N4148, 680 ohm and LED are optional components to indicate output signal and coil are present.
• All resistors are 1/4 watt, 5% .

Third party source of kit on eBay:
http://www.ebay.com/itm/Electronic-Water-Descaler-Decalcifier-Limescale-Remover-DIY-FREE-SHIPPING/272189006780