Author Topic: Sensor adjust options  (Read 2024 times)

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Offline frank26080115Topic starter

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Sensor adjust options
« on: October 21, 2007, 11:47:50 AM »
i have 6 phototransistors with a resistor network to act as the divider, the output is between the phototransistor and the resistor

but, if i wanted to lower all the output voltages, should i use diagram 1 or 2?
1 uses a variable resistor to add to the resistance to all of the other resistors, but i'm not sure because one change in one sensor might affect another sensor's output.
2 uses a potentiometer to adjust the upper limit but i'm not sure if it works.

1:


2:


this is for my new mini sumo bot, i need to be able to adjust the overall readings so it works in a high light enviroment, if the adc result is under 30 it goes into passive tracking mode and i don't want that to happen if it sees some spotlight or something.
« Last Edit: October 21, 2007, 11:51:25 AM by frank26080115 »

Offline paulstreats

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Re: Sensor adjust options
« Reply #1 on: October 21, 2007, 04:31:15 PM »
i would probably just get rid of all of the other resistors and use 1 suitable master potentiometer

Offline frank26080115Topic starter

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Re: Sensor adjust options
« Reply #2 on: October 21, 2007, 05:01:46 PM »
i want individual readings from all of them, i was just too lazy to add the outputs into my diagrams

eagle is a pain in the ass to use

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Re: Sensor adjust options
« Reply #3 on: October 21, 2007, 08:01:35 PM »
Both will work, but the 1st one wont waste power. Go with the first . . . but why do you want to lower the output?

Offline frank26080115Topic starter

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Re: Sensor adjust options
« Reply #4 on: October 21, 2007, 10:12:24 PM »
i want to raise the ADC readings so i can adjust for really bright rooms or outdoors

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Re: Sensor adjust options
« Reply #5 on: October 22, 2007, 08:20:15 AM »
hmmmm you might have problems with over saturation outside on a sunny day . . . but otherwise sounds reasonable . . .

Offline frank26080115Topic starter

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Re: Sensor adjust options
« Reply #6 on: October 22, 2007, 11:22:02 PM »
plan totally back fired, trim pot should have been on the ground end of the circuit, but since each phototransistor is already soldered onto the ground supply rail, i'll wire another trim pot to my analog reference and make the ADC use Aref instead of Avcc

 


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