I have taken up a "follow me" robot as my course project ,i am taking the following approach:

  1. Use one SR04 ultrasonic transducer only as transmitter which will be with me.
  2. Another SR04 module only as receiver which will be mounted on the robot.

I just know how to calculate distance using one transducer (SR04) ,but in this work I need to use only one as a transmitter and the other only as receiver.Is there any way where we could achieve above mentioned.

All I need is my robot should follow unique person and tracking distance less than One meter. If there is any other method welcome ..


2 Answers 2


I think this is the module that you are using. (please confirm - if it isn't I'll nuke this answer from orbit) The way that module works is that it sends a series of ultra sonic pulses , measures the distance from time of flight. The sent pulse and the received pulse have to be related and timed.

A separate transmitter and receiver will not be linked together so the receiver will get very confused.

So in short you cannot do as you want to.

You also have the problem of steering, this unit tells distance only directly in front of it, you have no way of knowing if the person it is following has moved to the side and in which direction.

I think that an optical system that tracks along a horizontal angle that only tracks a specific wavelength or pulse pattern will give you both the identity and the direction (for steering) that you need. Keep the US sensor to prevent the robot from running over the person of course.

  • \$\begingroup\$ Ok but using optical system will increase my cost of project and complexity i have to complete this project in a period of two months and i am completly new to Optical Sensor processing any alterative method.? \$\endgroup\$ Mar 7, 2013 at 18:14
  • \$\begingroup\$ How about a US transmitter (that doesn't interfere with the unit on the robot) - different wavelength. and an array of simple microphones on the robot in a arc. You steer until the central microphone has the maximum signal. You could also encode the US transmitter to have a unique pattern. \$\endgroup\$ Mar 7, 2013 at 18:26
  • \$\begingroup\$ Or you could IR transmitters receivers from TV remotes, also in an arc. \$\endgroup\$ Mar 7, 2013 at 18:28

I don't think that a single receiver on the robot will be good enough. All you get from that is that the signal was heard and possibly at what strength. How is that going to tell you which way to go?

Ultrasound could be a viable option, but at the least I would use two receivers. The speed of sound is slow enough that the time of arrival difference can be measured by a ordinary microcontroller. I suppose the simplest form is just to steer in the direction of the receiver that received the ping from the transmitter first. In this system, you'd have to use signal strength to guess you are too close and stop to avoid crashing into the thing you are following.

A more sophisticated system would use another sensor to resolve distance better than just by using signal strength.

  • \$\begingroup\$ I can use two ultrasonic sensors to achieve direction control,but how can i use Transducer only as transmitter, i.e: I do not know the time i send sound pulse out from transmitter without knowledge of it how to measure distance at receiver end one which is on Robot. \$\endgroup\$ Mar 7, 2013 at 17:41
  • \$\begingroup\$ @Balaji: You don't have to know when each pulse is sent. You compare the difference between the arrival times at the two sensors to determine which direction to go. \$\endgroup\$ Mar 7, 2013 at 18:52

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