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Water Level Controller with Reed Sensor

This is a way by which you can monitor the level of fluids like water in a tank. Based on data from the sensor you can control things like solenoids or motors as required or even turn on a buzzer, hooter or annunciator in a control panel. A simple Water Level Controller.


Look at the picture on the right, the float can be a Styrofoam type with a couple of ceramic magnets stuck inside. The float must move freely up and down a long plastic pipe of around 10 mm dia. If the fluid is not water but a solvent then design a non-soluble float or coat the float you made with something like an epoxy resin.

Water Level Controller

Then you need to assemble a small circuit within the long plastic pipe. Many reed relays with a chain of resistors in series has to be inserted in the pipe. The resistor and the glass reed relays should be in different levels of the pipe where you need an alarm or indication. Seal the pipe hermetically at both ends with epoxy resin after taking out a shielded cable of just 2 wires + 1 ground shield.

When the fluid level changes, the float moves up or down with it, when the float moves over a section of pipe where the reed relay is mounted, the magnets on the float make the reed operate and the resistance of the sensor changes.

The resistance is measured and the alarm can be operated as you like. The advantage of this arrangement is the electric circuit does not come in contact with the fluid, no sparking risk.

Reed Relay. It was invented by Dr. W. B. Ellwood at Bell Labs in 1936. Contacts are in a sealed glass tube filled with inert gas like in a bulb, so they do not corrode. It is faster than regular relays and as no spring is used it has a longer mechanical life. The two contacts are ferromagnetic blades plated with rhodium. When you take a magnet close by, the contacts touch each other. You can also put the reed in a coil, then when you energize the coil the reed operates. Used in telecommunication.OKI is one manufacturer of this type of component.

Design and Caution.

When you drive inductive loads you have to use RC snubbers, freewheeling diodes, varistors or zeners. when you drive lamps the cold current is high so use thermistors. The Reed relay is best used in telecom and instrumentation and avoided in power electronics. It can handle high RF frequency as the path of current is straight and footprint small.

Here is a Circuit to Build and Learn this Concepts – This can help make a Water level controller from sump to overhead tank. This can also be used in industrial fluid level control like oils and thick fluids. It may not work with highly viscous fluids or sticky mixes.

Fluid or Water Level with Reed Relays

“When you use the DMM or digital multimeter, try not to use it for high voltages and currents, use Solderman Talks 1702 external shunts and attenuators instead. If you try to measure 230V AC in the Ohms mode or in the Current mode with the probe in the current socket then you will see fumes in your DMM and a hole in your pocket !!”

– Solderman Talks 1702

Automobile Ideas from 2002

Cars should be aware of their environment and display status in the dashboard. It is like having cameras all around. The objects around and their direction of movement and acceleration.

Simple Automobile Safety Radar

There must be a very affordable automobile radar with just a 10-20 feet radius around the vehicle. This should display as a graphic on the dashboard as some of the very old 2D car games. This radar must be based on sonar or infra red to avoid additional EMI-RFI pollution and confusion. The display should show all objects which include people, small animals, kerb and wall.

The sensor has to be a multiple sensor, static belt one near wheels and one at the roof of automobile. The display device on car should be TCP-IP so that you can monitor your vehicle with your cellphone, PDA or any browser.

Automobile Ideas from 2002

Cars can have multiple skins like Winamp

If you use organic flexible LEDs, encapsulated in transparent poly-sulphone or some silicones. And the RGB triad matrix of LEDs are driven by a computer system to make it work like a flexible LCD screen. It can be used to form a skin for a car. Only there will be no high resolution, but it will do.

This flexible layer is fixed on the car like a permanent cap. Now with the onboard graphics synthesis embedded car computer you can choose any jpg, png or gif textured tile or make your own. Then output the tile or wallpaper to the car exterior LED matrix skin. Now the Car has become skinnable. Not just colors but fine textures are possible.


Now with a Bluetooth enabled Human Mood Monitor plugin you can make the car exterior to reflect the mood of the life-forms inside. This will make a road alive and traffic jams very colorful.

Some things i had written online around 2002 on cars.

Microcontroller – 8051, 8052, OpCodes, Analog Interface.

(:->)—-\–/—-< Man Sleeping