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Junk Bot

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Project Name:

Junk CD Bot

Author: 

Ron- The Maker

Project Description:

CD is used as a chassis. Motors have been selected appropriately. We are using 6V DC toy motors without any gearing down. The torque provided by the two motors is enough to drive a CD bot that is quite light weight.

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Assembly of CD Bot

CD is used as a chassis. Motors have been selected appropriately. We are using 6V DC toy motors without any gearing down. The torque provided by the two motors is enough to drive a CD bot that is quite light weight.

Bill of Material:

  1. CD- 2 in no.
  2. DC motor- 2 in no.
  3. SQPT Switches -2 in no.
  4. Screw and Nut (2.5 -3 inch)
  5. Hex Brasses
  6. Empty Pen and Refills
  7. A small box
  8. 9V Battery with connectors -2 in no.
  9. Pulley-2 in no.
  10. Bead
  11. Paper Clip- 1 in no.

Tool Box:

  1. Scissor
  2. Soldering Iron
  3. Screw Driver Set
  4. An Iron Nail
  5. Adhesives- Fevi-quick, M-seal

Construction Steps:

  1. Choose a shape for your robot (Top view) and mark it on the CD using a marker. While designing, it is appropriate to cut a CD sized white paper and carve shapes on it. As it is not easy to cut the CD, consider the place where motors are to be mounted. Leave enough clearance between wheel and chassis.
  2. Carefully cut out the marked shape on the CD with scissor. Caution: CD’s are brittle. The edges are really sharp.
  3. Since one CD will be stacked on another CD separated by stand-offs, mark 4-5 points for drilling holes on both the CD’s, where long screws will be put through.
  4. Use an iron nail as an iron punch as center punch to make the hole at the marked locations. Take utmost care not to break the CD with excessive force. Use a poker from your screw-driver set to enlarge the hole to an appropriate diameter.
  5. Choose on the CD as a bottom plate and mark the positions of the motor, where it shall be fixed. Stick the motors at the marked positions using an adhesive, ex- M-Seal.
  6. Bearing Construction: Take two pen refills with different diameters. Cut a piece of length, say L1, from a refill of bigger diameter and a piece of length, say L2, from a refill of smaller diameter, where L 1 is smaller than L 2. The small diameter piece should rotate freely when inserted inside the bigger diameter piece. Cut another very small auxiliary piece, say L 3, of refill with bigger diameter and fill it with M-Seal. After filling with M-seal, insert one end of L 3 into L 2. After m-seal sets properly, the other end of L 2 is put inside the L 1 portion. The protruding portion of L 2 must be fixed into the pulley and fix the pulley at this protruding end by applying some adhesive.
  • There are two visible portions of outer refill – one with pulley and other with small auxiliary piece called as fixed end or end piece. Stick the outer refill to the chassis. End piece prevents outer refill from falling out and inner refill rotates freely inside the outer refill. Make two such bearings.
  • Fix both these bearings parallel to the shaft line on the underside of the bottom plate/CD such that there is a scope of contact between the pulley and the shaft of the motor. In order to ensure proper contact, a pulley belt drive mechanism can be used to couple the shaft and the pulley. This is done by enlarging the diameter of the motor shaft by putting layers of tight fitting pen refills via use of heat shrink tubing.
  1. Castor Wheel Construction: To make the castor, put a small snugly fitting piece of empty pen refill through an appropriate bead. Unbend the paper clip and make a creative axle as shown below- Please check the drawing in the paint.
  1. Circuit Construction and Explanation:

The DC motors that are generally available are of Permanent Magnet type. The only way to control the direction of rotation is by controlling the current direction. If the current in a particular direction makes a motor rotate in one direction, say clockwise, then reversing the current direction would make it rotate in another direction, i.e., anticlockwise. Current direction in turn is determined by the polarity of the voltage applied.

Switches are classified by the number of poles and the number of throws. Poles refer to the number of nodes in a circuit that the switch allows you to switch simultaneously and the number of throws refer to the number of nodes per pole that the switch allows you to switch the corresponding poles to.

The switches that can be used may be SPST (single pole single throw), DPDT (double pole double throw), SPDT, DPST, TPTT, TPDT, TPST and so on.We’ll make use of a DPDT switch as we need to switch two nodes (the motor terminals) between the positive and negative terminals of the supply.

In one state of the switch (or one throw), one terminal of the motor is connected to the positive and the other to the negative of the battery. In another state, reverse connections are needed. Connect the motor terminals to the poles on the switch. Connect positive end of the supply to one of the other contacts and the negative end to the other contact on the same pole. Similarly, connect the supply to the contacts on the other pole with the polarity reversed.

Now the switch would give you a complete control over the motor direction. Repeat the same process for the other motor also. Mount the switches on a small plastic box and put the batteries into this box. You can put the batteries on the bot too,  if the motors are strong enough to move with the load. Now you have two switches that allow you to control where your robot goes. Running both motors forward makes it go straight ahead and running both of them backwards makes it go straight back. To turn left the right motor moves forward and the left one backwards. The opposite case makes the bot turn right.

9. Put the other CD onto the lower one separated by stand-offs made from pen-refills and coupled together by long screws that run through both the holes in two CDs.

10. Congrats! You have just made your first bot from junk. You are ready to roll!

Did you have junkfun as we promised?

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