Ultrasonic Range Finder/Backup Sensor Question

Discussion in 'The Projects Forum' started by Barrows_Basement, Feb 15, 2010.

  1. Barrows_Basement

    Thread Starter New Member

    Feb 8, 2010
    I've been working on this project for months and finally got it working. But I have a question about a few parts of the circuit since I collected bits and pieces of it from around the internet...I attached the complete circuit diagram and I'm wondering how the circled capacitors do not filter out the returning ultrasonic pulse and/or what's their effect since they're in series? Just trying to learn how this circuit works and if you have any questions about it please let me know...looking forward to hearing back from you all, thanks!
    P.S. All the values are calculated to detect an object at 5 feet. The 40kHz pulse is sent out for 1 millisecond and the "comparison pulse timer" is a monostable pulse that goes high for the total time it takes a sound wave to travel 5 feet out and 5 feet back, (9 milliseconds).