Monday, March 5, 2012

Helicopter Auto Pilot - Infrared Emitter

Back to Helicopter Auto Pilot - Introduction
Download source code & runtimes: Heli Control

Infrared Emitter (L-i-h)
In the original video I posted I was using the USB IR Toy together with a simple circuit that amplifies the IR signal with some extra IR Leds. In version 1 of the USB IR Toy couldn't do this so I had to reprogram the IR Toy to send the signal through the TX serial pin which had a header on the board where you could connect the amplifier circuit. This was a rather complicated development that required using the MPLAB IDE and C compiler to reprogram the PIC18F2550 at the heart of the IR Toy. Unfortunately for me during testing that part of the circuit was fried.

Based on a suggestion posted on the original video I decided to use instead the laptop's headphone jack to send the signal to a homemade IR emitter.

I must warn you, my knowledge of electronics is pretty limited so I'm sure this circuit can be improved upon and I'm open to suggestions. This circuit was designed with the assistance of the nl5 circuit simulator by Alexei Smirnov:

The circuit is simple enough:
  • T3 & T4 form a classical BJT astable multivibrator (oscillator) at ~ 32KHz. 
  • T1 & T2 perform an AND operation with the incoming signal (Base).
  • D1 & D2 serve to create a constant current driver for the IR Leds (D3-5).
To connect this circuit to the audio jack connect the Left wire to Base, Right to ground and ignore the ground wire.

PS. With a small modification this circuit also becomes compatible with the  i-Helicopter app for Androids and iPhone. The app is free and it uses the same protocol as my FalconX helicopter .


Tim said...

What kind of diodes are D1 and D2? Are they protection/power diodes?

TechMind said...

This is what I used:

Will said...

how would you do this on a raspberry pi?
i have already made the emitter but need a program like yours to read it anyone help me please