Follow me indoor trolley.

Projects General Guidance
1

Hello everyone!

I am currently trying to embark on my first big Arduino project. It involves a trolley that is able to follow someone indoors. I am trying to avoid GPS as it is inaccurate indoors and WIFI-based systems as that would mean its localized into one location. Right now i am looking towards Ultrasonic emitters and receivers. The idea is to have an ultrasonic emitter emitting ultrasonic waves and have 2 receivers triangulate the person's position; if the left receiver received the wave first, it would turn left ,vice -versa.

something like this

I have 2 main questions

  1. Is ultrasonic emitter/receiver the way to go?
  2. If it is , currently, i have multiple HC-SR04 sensors lying around. Is it possible to make one of them purely transmitting and the other purely receiving ? I have been looking around the web and it doesn't seem feasible.

Thanks!!

2

EightFingers:
I have 2 main questions

  1. Is ultrasonic emitter/receiver the way to go?

That's usually combined with a radio signal so you can actually measure distance between transmitter and receiver.

  1. If it is , currently, i have multiple HC-SR04 sensors lying around. Is it possible to make one of them purely transmitting and the other purely receiving ? I have been looking around the web and it doesn't seem feasible.

You can. You have to disable the transmitting side on the one you only want to receive, and make sure you send the trigger signal at the same time (it triggers on the falling edge) to have it actually listen and send back a signal.

3

Hmm okay. I am going to experiment around, I will get back here if there is any problem.

4

Just unsolder (or cut the traces of) the Transmitter on one and the Receiver on the other. If you wire one Arduino pin to the Trigger pin on both units you should be able to use the Echo pin on the receiver unit to measure the distance between the two. Note that this is one-way distance and with a single unit you are measuring round-trip distance. If you don't correct the math your distance will be off by a factor of 2.

Replace the Trigger wire on the two Receiver units with a radio (or IR?) link to trigger all three at the same time. You can save some power on the Receiver units by removing the MAX232 chip which is only used to drive the Transmitter.

5

EightFingers:
I am trying to avoid GPS as it is inaccurate indoors

You avoid using GPS indoors because it normally does not work at all.