Here is the text for a infrared transmitter and receiver for controlling a standard servo at a carrier frequency of about 38khz. This frequency is used to avoid other lighting from interfering with the control process. Using a 555 Ic the control timer is a typical servo testing circuit producing a positive square pulse varying in width from about 1ms to 2ms at 20ms apart to position the servo. Another 555 IC timer produces the carrier frequency and is switched on off by the control timer for modulation by a cmos 4066 analog or digital switch rather than the enabling and disabling method. The carrier frequency can be simply monitored this way. The output is amplified for the infrared led for the transmission to the receiver'
The signal is received by a special IC tuned to abut 38khz which outputs the pulse in a negative direction. This is made positive and amplified by a cmos 4049 inverter. This is then feed to the servo which has a separate supply to avoid upsetting the earlier circuitry by unwanted spikes etc. I had big problems originally amplifying the signal using ordinary transistors. The cmos inverter buffer fixed this.
I am going take the liberty to submit this text now and send the photos and diagrams in new topics because of the problems I have inserting images and end up losing the lot. It was difficult enough getting the circuit to work and then having more problems trying to post it all. . Also next I will use the picaxe method of doing the same thing. Hope to have sorted the posting problem by then. Regards Nedpicaxe
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