Problem about choosing a light wave or ray.

Replies

• 

  Aashish Joshi

  are you talking about this :
  
  Proximity Sensor
• 

  silenthorde

  Hey Austin...
  
  Human skin reflects light and a lot of it. That is the principle reason why we can see each other. Any light source and a sensitive photodetector placed close to the human skin should work.
• 

  vb_austin

  so can i use a laser light for this purpose.will it reflect from human skin..
• 

  Ashraf HZ

  Yes, it will reflect human skin. Though if you intend on using on a motorbike, make sure they are rated safe for human eyes.
  
  Other things to take into account when selecting your photodetector is a detector which has a very quick response time and sensitivity in relation to the laser you choose. You'll need to do some research on this 😀
• 

  silenthorde

  ash

  Other things to take into account when selecting your photodetector is a detector which has a very quick response time and sensitivity in relation to the laser you choose. You'll need to do some research on this 😀

  Rightly pointed out by ASh, photodetectors(even cheap LDR's ) have very high sensitivity and require quite some calibration to work with. The problem I personally have faced here is the lack of branded photodetectors. Here they sell cheap local variants for Rs5 a peice. The problem is that, you don't get the manufacturer's datasheet. So you'll have to painstaikingly go through the calibration process on your own.
  
  Even slight movement of the light source, micro order possibly will show changes at the photodetector output.
• 

  silenthorde

  Keeping your application in mind I feel that an Ultrasonic Transmitter, receiver pair should be used. I believe your application requires detection of obstacles in front of the vehicle and actuation of brakes automatically. A doppler transceiver will be ideal for this purpose.
  
  Other CEans. Please comment.
• 

  Ashraf HZ

  Yes, that might be an easier approach. Though in addition, you'll need to guide the ultrasonic waves only to the path of the motorcycle, or else there will be a lot of false detection when going through a narrow path.
  
  Something else to take into account is which speed should be chosen to activate this automatic braking, regardless of which sensor we use. If we assume a certain speed, that will help us determine the distance (max & min) and hence the required calibration.
• 

  vb_austin

  ya guys i thought of using ultrasonic waves..since it can cover larger radius..
  A big doubt is there for me in automatic brakes i.e.. we need to overtake a forward vehicle when we move closer distance is reduced so ultimately brakes is applied but our intention is to overtake.how can this problem be solved.also in case of traffic lights and speed breakers too how can the automatic brakes be applied.