ir sensor range

Which IR emitter and receiver are you using?

Are you using an IR receiver that has noise cancelling circuitry and requires a pulsed IR emitter for maximum sensitivity? The pulse is usually 38 KHz more or less. And that pulse stream itself must be turned on and off at a defined rate. That is all explained in the datasheets.

John

 

Can the local shop tell you the part numbers? It's unusual for a shop to sell you parts but not know what they are.

Infra-red may not be the best way to detect obstacles. If the obstacle is matte black it won't reflect any light so it will be invisible.

John is talking about pulsed (amplitude-modulated) infra-red. This is the system used with infra-red remote controls. The IR transmitter is turned ON and OFF at a "carrier" frequency of around 40 kHz and the receiver has a bandpass filter so it detects only IR light that is modulated with that carrier frequency. This allows the receiver to reject other sources of IR light such as incandescent or fluorescent lights and sunlight, so it can give much greater range.

You can buy IR receiver units that have the filter and detection circuitry included, and you may be able to generate the carrier directly with the PIC using a timer. Otherwise you might be able to derive it from the PIC's clock using a frequency divider.

This method might give you better range. I'm not sure it would be reliable for detecting obstacles though. Have you considered ultrasonic?