# circuit Making an obstruction avoiding device without microcontroller

Posted on Feb 4, 2014

Make a toy device which spins to the left whenever there is an obstruction in front of it, without any microcontroller. Can anybody please check whether my approach in building the device is correct or not [let`s assume we are driving our device in a bright room with uniform lighting] Any tips or suggestions for improvement (if it is correct) will also be appreciated.

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My approach is to use two DC motors as the rear wheels of the device. Attach an LDR to the front of the device and connect it to the left motor. Now both the motors are connected to a power supply. When the power supply is switched on and no obstruction is in front of the toy, both the motors will be moving at approximately same speed since the LDR will be in exposure to light and its resistance will be negligible, because of which the toy will run straight. Now when there is some obstruction in front of the device, the amount of light falling on the LDR will decrease, which will imply a rise in resistance of the LDR. Thus the velocity of the left motor will decrease, while the velocity of the right motor will be moreorless constant. So the device will spin to the left. The circuit diagram corresponding to my argument is provided in the link below. I will post the mechanical simulation of the device shortly (within 2 hours from now). In principle it will do what you expect but you`ll need to use the LDR into an amplifier so that the motor is controlled because its resistance is unlikely to be able to power much even when totally illuminated Andy aka Jun 1 `13 at 16:02 I am the one who asked this question [sorry for asking through the fake account, I was in a hurry actually]. Since I can`t comment I am posting it as an answer. @Andy aka, The LDR is not used to power the motor, instead it is used to reduce the velocity of...

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