how do i manage with only 1 adc port?

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i am trying to build a grid navigating bot .
i need to use around 11 sensors.(i think i require 11 adc pins).i use atmega 16

how can i sense the values(white/black) without the use of adc?

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Can you tell us types and model numbers of the sensors? I am thinking (meaning I haven't done it before) that unless the sensors have some built in electronics you would have to provide some sort of comparator circuits between the sensor and the AVR. The output of the comparator could be fed directly into an AVR port pin, no need for ADC. Of course the down side is that there is no "on the fly" adjusting of sensitivity or selectivity unless you use some microcontroller based "set point" adjustment (DAC or PWM based). Since all the sensors would probably be the same you might be able to use just one DAC or PWM channel for all 11 sensors.

Again, I am just thinking out loud. I am sure someone with experience in this field could provide more definitive answers. I would still think it would be difficult for someone to help without you providing more detailed information.

edit: Another course of action would be to use external analog multiplexers to route the 11 sensor signals into just 1 ADC pin on the mega16. I am thinking you would be able to cycle through all 11 channels fast enough for your purposes but that is just a "gut" feeling.

Regards,
Steve

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Use a mega1280.... 16 a/d channels?

Imagecraft compiler user

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Use a multiplexor IC.

For a recent mobile robot project we used the Linear Technology LTC221 to connect 4 ultrasonic sensors to 1 ADC port. While the LTC221 allows 4 to 1 multiplexing, I'm sure you could find at least an 8 to 1 multiplexor out there.

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Another option would be using external (small) A/D converter with e.g. IIC bus interface. You could then place the converters close to the sensors instead of routing (probably unamplified and unfiltered) analog sensor signals all over the place. But for simple 0/1 the comperator solution is a good and simple choice.

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Hellfleck wrote:
Another option would be using external (small) A/D converter with e.g. IIC bus interface.

That external ADC could also be another AVR.

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With some sensors, one can use normal port pins to choose the one Sensor that is active. With resistive sensors one side of each sensor is tied to one digital output with 3-state capability and the other to the common input. With optical reflex sensors one can have all recievers in parallel and just power one LED at a time. This will of cause give more background signal, but this is only one common background.

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i am planning to use either ir-led & phototransistor pair or photoreflectors.