## 24 Jan 2012

### How to Make an Odometer

This is a really interesting calculator hack and this concept can be useful in diverse projects. If you were looking for a means to find out how much you travel on your bike, then this is just the right place. All you need to spare is a dirt cheap calculator and 20 minutes of your free time.

Materials Required:
• A calculator
• A reed switch
• A powerful magnet (preferably light and small)
• A couple of wires
• And a bicycle :P

Tools Required:
• Soldering iron and solder
• Double sided tape
• Duct tape or any strong tape

Step by step instructions:
 Calculator PCB
• Open up a calculator and locate the equal sign button on the PCB
• Locate the 2 holes that are linked to this button (tricky)
• Take 2 wires of lengths depending on the distance from the calculator to the magnet
• Solder each of the 2 wires to the 2 holes of the equal sign button
• Twist the other ends of the wires with the legs of the reed switch and solder both the joints
• Put back the cover of the calculator and switch the device on.
• Press the '+' button, then  '1' and then bring the magnet back and forth to  the reed switch and the number on the LCD display should keep increasing by one. If you succeed doing this then your odometer is almost complete!
• Now fix the magnet on one of the spokes of your bike close the axle with some tape.
• Fasten your calculator firmly on your chain guard (or any other flat surface) with the double sided tape
• Tape the reed switch as close to the magnet as possible yet at a safe distance from the spokes
• Again switch the calculator on, press the '+' button, insert the 'circumference' of your wheel preferably in meters and RIDE ON!!
 Sorry, I couldn't find a cleaner bike!! :P
Every time the magnet comes close enough to the reed switch, the '=' button is shorted and the circumference of your wheel is added to the distance you have traveled. Your bicycle odometer is complete!

NOTE: At high speeds the reed switch will not always get triggered by the magnet and the odometer might display faulty results.

## 19 Jan 2012

### Tilt Sensor Alarm

Some time back I came across an article in a magazine where a boy lost his leg thanks to his habit of balancing on chairs. I thought why not build a tilt sensor alarm for chairs before calamity struck me too. So I came up with this simple tilt sensor circuit which doesn't really need any instructions to build.

Materials Required:
• A Piezo Buzzer
• A 9v Battery
• A 9v Battery Connector
• A small and thin magnet
• A small box to keep the circuit compact
• Aluminium foil or any small conductive sheet

Tools Required:
• Insulation tape
• Double sided tape
• Soldering iron and solder instead of insulation tape

Step by step instructions:

The Tilt Sensor Circuit

 A Close-up of the connectors.
• Scrap off the paint of a dead battery
• Cut two pieces of aluminium foil of about 1cm X 1cm
• Connect the positive end of the battery connector to the positive end of the piezo buzzer by twisting the copper strands together or by soldering
• Fix the magnet on one side of the box as indicated in the images above so that the battery remains stuck to the contact points for a while
• Stick the negative ends of the buzzer and battery on either side of the magnet keeping in mind their alignment with the rolling battery
• Stick the aluminium foils on top of the negative ends to improve connectivity on the contact points
• Arrange the circuit in your box as indicated in the images above and do the necessary for aesthetic beauty :)

 Hard Luck for those who love to balance on chairs!

Now you can place this circuit wherever you like and use it as a tilt sensor. Of course the smaller the piezo buzzer, the battery and the rolling element, the more compact the circuit box. Simple as that!

## 4 Jan 2012

### Build a Water Level Indicator

If you don’t have an automatic water level controller installed at home and are concerned about the gallons of water that are wasted daily, then here is the ideal water level indicator to build. This is the most basic and economic circuit I could think of. But if you want to build a reliable automatic water level controller, check out: The DIY Water Level Controller.

Materials Required:
• 9v Battery
• 9v battery connectors
• 1 piezo buzzer
• 1 toggle switch
• 2 wires (of the same length as the distance between your tank and your room)
• 2 long nails (or any 2 metal rods)
• a box for keeping the circuit compact
• Tape for fastening the probes on the tank

Tools Required:
• Common Sense
 A diagram of the system

Here is a step by step guide to make the circuit:
• Cut the wires to the required lengths and strip off their ends.
• Make a hole on one side of the box for the 2 wires to come out.
• Cut a precise hole on top of the box so that the switch fits perfectly into it.
• Fix the switch into the slot.
• Connect the 9v batteries in series.
• Connect the positive end of battery pack to the positive end of the buzzer.
• Connect the negative end of the battery pack to the switch.
• Connect one end of one long wire to the switch.
• Connect one end of the 2nd long wire to the negative end of the buzzer.
• Coil the two ends of the long wires around 2 long nails and tape them to make a safe joint. Leave at least half of the nails bare to maintain a good continuity in the water.
• Place the buzzer and the batteries in the box.
• Fasten the nails to the inside of your overhead tank such that the nails are just below the level of brimming of the water.

 The box containing the "circuit"
Now whenever you switch on your pump remember to switch on yourand when the alarm goes off you can put off your pump and no water is wasted!
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