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Topic: interfacing a sensor (Read 2 times) previous topic - next topic

kavya_mc

yes sir I have connected the sensor outputs directly to arduino.......
can you please tell me what the bridge exciter circuit is.?
Also I wanted to know if the PC can detect two arduino boards simultaneously connected to it?
thank you

Grumpy_Mike

On page 2 of the data sheet at the top there is a diagram. Everything inside the dotted line is your sensor. Everything outside the dotted line is your exciter circuit. In this case it consists of an amplifier and voltage reference that powers or excites the bridge circuit.
However the data sheet also says you get 50mV full scale output from the bridge. That means that at the maximum pressure output you will only get a reading of 10 from the arduino's A/D converter. So it is not very suitable for direct connection.
This sort of sensor needs an amplifier if it is to be of any practical use.
This is a link to the sort of amplifier circuit you need:-
http://www.flickr.com/photos/33177304@N03/4666641155/

Quote
Also I wanted to know if the PC can detect two arduino boards simultaneously connected to it?

Yes it can but only one can talk to the serial monitor built into the arduino IDE. The second will have to use another terminal emulator like freeTerm.

kavya_mc

i connected 2 arduino uno boards to laptop and tried loading blink sketch by opening 2 arduino IDE windows. it worked on one board with COM 15. but for the other its not. i tried selecting COM 4,5,6,9,10,11. but it is showing the error as "avrdude: stk500_getsync(): not in sync: resp=0x00" what should i do so that I can work on both boards simultaneously?

michinyon

I don't understand,  when you say you want to read the sensor,   and then send a message to the arduino if it changes.

Isn't it the arduino which is reading the sensor?   Do you want to send a message to another arduino,  when it changes ?

michinyon

You have connected your sensor wrong.

The connections + and - of the sensor,  you should connect the -ve to your arduino ground  and the +ve to your arduino analog input pin.

You will then read the voltage output by the device.

The other problem is,  the output of this device is 50 millivolts at full scale.   On the arduino analog input,  this will give you a reading of between 0 and 10  (  counts out of 1023 ) only,   because the full range of this device is only 1/100th part of the full analog input range 0 to 5 volts.

The actual values you got, are the difference between your sensor1 and your sensor2 ,  which is 5 or 6 counts on the examples you got,   so it actually looks like it is working.

You can improve the effective A/D range by understanding and using the arduino AREF pin.    You could also use an external amplifier circuit using an op-amp  to increase the size of the signal which the arduino is receiving.





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