Hi Everybody!Iam working out a design for servo controller which receives signal from R/C receiver in manual mode & a microcontroller generates signal in auto mode. One channel of receiver to be used for switching between modes.Following idea came in my mind:An AND gate with 2 inputs whose one input is nothing but the receiver signal, another input from microcontroller as ENABLE.The output of AND gate is common to the servo and a microcontroller I/O pin.Working:One channel of the receiver will be connected to micro for swtching between modes.MANUAL MODE: The ENABLE input to the AND gate goes high(1), so the signal from receiver appears at the output of AND gate. In this mode the micro pin which is also connected to the output of AND gate becomes input pin & reads the pulse from receiver. Servo is driven by receiver signal.AUTO MODE: Before switching, the micro stores the last input from receiver as reference. The ENABLE pin goes low(0) and the receiver signal stops appearing on the output of AND gate. Now the micro pin which is connected to the output of AND gate will become an output pin & drive the servo.What I have described above is the unit required for one servo. Using a quad AND gate IC like 7408 we can have a servo controller for 4 servos. It will require 4 I/O for ENABLE, 4 I/O for signal, 1 I/O for switching and UART to receive servo positions in auto mode. One more benifit which I observed is that we can have some channel manually controlled even in the AUTO mode. This feature can be helpful while testing.
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why not use the micro stepper motors and a pic from Electronic Goldmine. that is what i am doing. You can do it directly off the pic. For larger servos, i don't know, i just buy controllers off of ebay or second hand from places.
If you want to do it with TTL try the 74ls157, it's a quad 2-1 multiplexer, you can select between two input lines using only 1 uC output. Remember, whatever you want to do with TTL, there's a 74 series ic that will do it for you.
I think we've already done this with Jordi's MUX, which is open source, very cheap and does all that and more. Check it out and see if suits your needs.
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