DIY Float Switch: Everything You Need to Know

What is a Float Switch?

A float switch, also known as a level switch, is a device that monitors the level of liquid in a container and activates or deactivates an electrical circuit based on the liquid level. It consists of a floating mechanism, such as a ball or a rod, that rises and falls with the liquid level. When the float reaches a predetermined level, it triggers a switch, which in turn sends a signal to the connected device, such as a pump or an alarm.

Types of Float Switches

There are several types of float switches available in the market, each designed for specific applications and environments. Some of the most common types include:

1. Vertical Float Switch: This type of switch is mounted vertically in the container and is suitable for narrow spaces. It consists of a float that slides up and down a shaft, triggering the switch when it reaches a certain point.

2. Horizontal Float Switch: This type of switch is mounted horizontally in the container and is suitable for wide spaces. It consists of a float that pivots on a hinge, triggering the switch when it tilts to a certain angle.

3. Cable Float Switch: This type of switch is suspended by a cable in the container and is suitable for deep spaces. It consists of a float that rises and falls with the liquid level, triggering the switch when it reaches a certain height.

4. Magnetic Float Switch: This type of switch uses a magnet inside the float to trigger a reed switch mounted outside the container. It is suitable for corrosive or viscous liquids that may damage mechanical switches.

Working Principle of a Float Switch

The working principle of a float switch is based on the buoyancy of the float mechanism. As the liquid level rises, the float rises with it, and when it reaches a certain level, it triggers the switch. Conversely, when the liquid level falls, the float falls with it, and when it reaches a certain level, it triggers the switch again.

The triggering mechanism of a float switch can be either normally open (NO) or normally closed (NC). In a NO switch, the circuit is open when the float is at its lowest position and closes when the float reaches the triggering level. In a NC switch, the circuit is closed when the float is at its lowest position and opens when the float reaches the triggering level.

Applications of Float Switches

Float switches are used in a wide range of applications, including:

1. Sump Pumps: Float switches are used to control the operation of sump pumps, which are used to remove water from basements or crawl spaces. When the water level rises, the float switch triggers the pump to turn on and remove the water. When the water level falls, the float switch triggers the pump to turn off.

2. Water Tanks: Float switches are used to control the filling and emptying of water tanks. When the water level falls below a certain point, the float switch triggers a valve to open and fill the tank. When the water level reaches a certain point, the float switch triggers the valve to close.

3. Irrigation Systems: Float switches are used to control the operation of irrigation pumps. When the water level in the irrigation reservoir falls below a certain point, the float switch triggers the pump to turn on and refill the reservoir. When the water level reaches a certain point, the float switch triggers the pump to turn off.

4. Wastewater Treatment: Float switches are used to control the operation of wastewater treatment systems. They are used to monitor the level of wastewater in tanks and trigger pumps or valves to transfer the wastewater to other stages of the treatment process.

5. Aquariums: Float switches are used to control the water level in aquariums. When the water level falls below a certain point, the float switch triggers a pump to refill the aquarium. When the water level reaches a certain point, the float switch triggers the pump to turn off.

How to Build a DIY Float Switch

Building a DIY float switch is a relatively simple process that can be accomplished with readily available materials and tools. In this section, we will provide a step-by-step guide on how to build a vertical float switch using PVC pipe and a microswitch.

Materials Needed

• PVC pipe (1″ diameter, 12″ length)
• PVC end cap (1″ diameter)
• PVC coupling (1″ diameter)
• Microswitch (SPDT, 5A)
• Float (1″ diameter, polypropylene)
• Wires (18 gauge, stranded)
• Solder
• Heat shrink tubing
• PVC cement
• Drill
• Drill bits (1/4″, 1/8″)
• Wire stripper
• Soldering iron

Step-by-Step Instructions

1. Cut the PVC pipe to the desired length (e.g., 12″) using a saw.

2. Drill a 1/4″ hole at the top of the pipe, about 1″ from the end, for the microswitch.

3. Drill a 1/8″ hole at the bottom of the pipe, about 1″ from the end, for the wires.

4. Clean the ends of the pipe with PVC primer and apply PVC cement to one end.

5. Attach the PVC coupling to the cemented end of the pipe and let it dry.

6. Apply PVC cement to the inside of the PVC end cap and attach it to the other end of the pipe. Let it dry.

7. Strip about 1/2″ of insulation from the ends of the wires and solder them to the terminals of the microswitch.

8. Cover the soldered connections with heat shrink tubing and shrink it with a heat gun.

9. Insert the microswitch into the 1/4″ hole at the top of the pipe and secure it with hot glue or epoxy.

10. Feed the wires through the 1/8″ hole at the bottom of the pipe and seal the hole with hot glue or epoxy.

11. Attach the float to the pipe using a hose clamp or zip tie, making sure it can slide freely up and down the pipe.

12. Test the float switch by connecting the wires to a multimeter or a circuit and moving the float up and down. The switch should open and close at the desired levels.

Frequently Asked Questions (FAQ)

1. What is the difference between a NO and NC float switch?
   A NO (normally open) float switch is open when the float is at its lowest position and closes when the float reaches the triggering level. A NC (normally closed) float switch is closed when the float is at its lowest position and opens when the float reaches the triggering level.

2. Can a float switch be used with any type of liquid?
   Float switches can be used with most types of liquids, including water, oil, and chemicals. However, some liquids may require specialized float materials or switch designs to ensure compatibility and reliability.

3. How do I choose the right size of float switch for my application?
   The size of the float switch depends on the size of the container and the desired triggering levels. Generally, larger containers require larger floats and longer switch shafts. It is important to consult the manufacturer’s specifications or seek professional advice when selecting a float switch for a specific application.

4. How often should I replace my float switch?
   The lifespan of a float switch depends on the application, environment, and usage frequency. In general, float switches should be inspected regularly for signs of wear, corrosion, or damage, and replaced as needed. Most float switches have a lifespan of several years with proper maintenance.

5. Can I use a float switch to control multiple devices?
   Yes, a float switch can be used to control multiple devices by connecting them in parallel to the switch. However, it is important to ensure that the total current draw of the devices does not exceed the switch’s rating. In some cases, it may be necessary to use a relay or contactor to handle higher currents.

Conclusion

Float switches are essential components in many liquid level control systems, providing reliable and automatic operation. By understanding the types, working principles, and applications of float switches, you can select the right switch for your specific needs and even build your own DIY version.

When building a DIY float switch, it is important to follow the step-by-step instructions carefully and use appropriate materials and tools. With proper installation and maintenance, a DIY float switch can provide years of reliable service in various applications, from sump pumps to irrigation systems.

As with any electrical project, it is important to follow safety precautions and consult professional advice if unsure about any aspect of the design or installation. By doing so, you can ensure the safe and efficient operation of your DIY float switch and the devices it controls.