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1  Using Arduino / Sensors / Re: analogreference and resolution question (STILL NEED HELP) on: July 28, 2011, 05:35:25 pm
oh sorry it was 741.

And i dont really understand what you are saying. divide what voltage? I understand what a voltage divider is. but why?

As of what i have now im getting a output signal of 4.5 volts with no input. what is going on?

Then if i disconnect the V- from ground the output drops to 3 Volts.

help please?

im confused.
2  Using Arduino / Sensors / Re: analogreference and resolution question (STILL NEED HELP) on: July 28, 2011, 02:43:07 pm
So i decided to go with an op amp. specifically the lm781cn from radioshack.

What i have done so far is:

V+ to the +5V pin
V- to ground
inverting input to output with 100K resistor, then 1K to ground
non inverting is the signal

Is there anything wrong with this setup or am i good to go?

Thanks
3  Using Arduino / Sensors / Re: analogreference and resolution question (STILL NEED HELP) on: July 27, 2011, 05:42:41 pm
So like this?

http://www.radioshack.com/product/index.jsp?productId=2062547

How would I even hook that up?

I hate how they never give you specs...
4  Using Arduino / Sensors / Re: analogreference and resolution question on: July 27, 2011, 05:22:43 pm
Ok, so how would I amplify the signal coming out of the shunt? And just for practice, how do I lower the 5V pin to around 100 mV for the aref pin.

Thanks
5  Using Arduino / Sensors / analogreference and resolution question (STILL NEED HELP) on: July 26, 2011, 09:54:11 pm
Hi everyone,

Im new to arduino and I wanna know something about analogread and reference. I have an input from a shunt that measures amps of a circuit.  It outputs a value between 0 and 50 mV.  I wanna use the analogreference and the aref pin to lower my upper limit to 50 mV, So then I can read in raw voltage between 0 and 50 mV with 1023 steps because its 10 bit?

Is there a way to set aref to 50 mV using a 5 volt power supply?

Also, do I need a resistor in the analog input? safety? or a diode? im not sure.

Thanks
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