I am using an infrared tx-rx circuit as an obstacle avoidance for my mobot. the equipment used are infra red led, an infrared receiver module and resistors and lm555. the fact is that when i use the the circuit, i only get a high output from the infrared rx irrespective of whether when the IR led is on or off.i think the ir sender doesn't send with 38khz coz it's works with the remote control please help me to get the ir diode to send with 38khz frequency . this is my circuit http://www.mediafire.com/?w1n9aurjyz6ee75