Making A LDR Robot Which Works on Commands from a Smartphone

 Making an LDR Robot

• A Light Dependent Resistor (LDR) works on the principle of photoconductivity. The Light Following Robot's working principle is called PHOTO-TAXIS.
•  Photo means Light. The robot moves towards the brightest light source. It uses two LDR (photo resistors) and two transistors - one for each motor. 
• When light falls on LDR's, the circuit's resistance drops down and through the Transistor approx. 1Amp current flow,s thus the motors rotate, and the robot moves.

Hardware Required

1. Connecting wires
2. Stripper
3. 2 nos. NPN BC 547 Transistors
4. 2 Light Dependent Resistors
5. Paper Circuit Template
6. Copper Tape
7. Soldering Gun
8. Soldering Metal
9. Switch
10. Hot Glue Gun
11. Small Screws 4 nos.
12. Caster Wheel
13. Big Screws 7 nos.
14. Nuts 11 nos.
15. Metal Chassis
16. Paper Tape
17. 60 RPM Motors 2 Nos.
18. Robot wheels 2 nos.
19. Cable Tie 2 nos.
20. 3-D Printer
21. 4 V Batteries 2 nos.
22. Battery Holder
23. Drilling Machine

Procedure

1. Cut out the paper circuit template from the A4-size paper. You can find the paper circuit by clicking on the link: https://acrobat.adobe.com/id/urn:aaid:sc:AP:a9fd1e48-7680-499a-8ef9-b281adabb0ea

1. Next, paste the copper tape wherever there are dark lines on the paper circuit template. Check the connectivity of the paper circuit using a multimeter. For better connectivity, solder the points where the two copper tapes meet.
2. Now, attach one LDR to the left-hand side of the paper circuit. Make two holes on either side of the copper tape. Insert the LDR in such a way that its top surface faces the back side of the paper. After adjustment, press the LDR to make it hold tightly with the paper. Cut the extra terminals of the LDR and then solder them to the copper tape. Similarly, attach and solder the LDR on the other side as well!
3. Next, we have to attach the NPN BC 547 transistors on both sides. On the left side, turn the transistor 180 degrees in your hand and solder its terminals to the respective copper tapes.
4. On the right-hand side, the transistor should be attached and soldered straight, as it is, to the copper tapes. While soldering, see to it that the transistor does not overheat, or it will stop working.
5. Further, solder the negative terminal of the battery holder to one terminal of the switch. Take another wire, connect one end of the wire to the second terminal of the switch, and the other end of the wire should be connected to the center copper taped line.
6. Next, connect the positive terminal of the battery holder to the topmost horizontal copper strip, which is connected to both the LDRs.
7. Take one motor of 60 RPM. Connect two wires of the same adequate length to both the terminals of the motor with the help of a solder gun. Now connect one wire of the motor to the opposite transistor, and one wire should be connected to the center copper strip, which is connected to the second terminal of the switch. You are expected to do a similar process with the second motor and attach it.
8. The paper circuit is ready.

3-D Printing The Phone Stand

• Design the structure on which your smartphone can be kept using TinkerCad. It should be as given below:
• 3-D print the phone stand. It takes around 1 and a half hours to be printed.

• Further, paste the paper circuit on the smartphone stand in such a way that both of the LDRs are on the front and all the other circuits should be hidden behind the stand.
• After pasting the circuit on its stand, apply hot glue on one end of the switch and paste it on the top of the left-hand side of the phone stand.
• Further, apply double-sided tape under the battery holder and stick it on the other panel of the phone stand.

• Now, attach this phone stand to the red chassis. Carefully drill 4 perfect holes in the phone stand where the 4 small screws and nuts can be attached and tightened on the chassis.
• Similarly, attach both the motors on either side of the chassis using the big screws and the nuts.
• Further, attach the wheels to the shaft of the motor.

You can use the gyroscope voice command app to command your LDR robot and make it work. Keep the phone on the stand, command the robot, and the LDR robot would work as you say!!