Hi everyone.
This is my 1st post here and let me preface, I've searched my brains out.
It's been a while since I was knee-deep in electronics, and I have had to use Op or In amps previously, but I'm shaking off the rust.
I have an Arduino project where I want to log current in a circuit and am using an AD236AN.
If I should use something other than an AD236, I'm open to suggestion.
The circuit is one following this tutorial:
http://www.vwlowen.co.uk/arduino/current/current.htm
I tried contacting the author and banged my head on the desk the last few days.
Goal:
Make a kit I can insert between a device's PS and the device that will measure the device's current consumption via Arduino and send the data to a logging server.
I'd prefer to not have to worry about the tested circuit's supply voltage and instead worry about voltage drop across the shunt to calculate current.
Parts:
- Arduino Uno
- AD236AN
- .01Ω current sense resistor
- 100 nF ceramic cap
- 28 turn Variable resistor
- Testing load source
I tried this out on 2 different circuits because even 2 LEDs don't have much current draw which means the drop across the shunt is very low. (<2mV)
With the .01Ω shunt I (attempt to) use a 100x gain meaning the voltage across the shunt with gain100 should be the current of the circuit it's plugged into.
(The writeup uses gain of 10 and then multiplies that by 10 in the Arduino code)
The 2 circuits differ in that 1 uses a flashlight bulb(2.4V) and 2 D cells for its power source
and the other uses 2 parallel LEDs powered by the Arduino 5V with a 110Ω resistor.
Problem:
I cannot get the gain to follow the datasheet.
for gain 100, I should use 1.02KΩ for R1 but instead it comes out to ~gain 200.
If I instead double up and use 2020Ω it comes out right?
(I got that from this example sheet of basic InAmps: pg19 http://www.analog.com/static/imported-files/application_notes/AN-244.pdf)
This is my 1st post here and let me preface, I've searched my brains out.
It's been a while since I was knee-deep in electronics, and I have had to use Op or In amps previously, but I'm shaking off the rust.
I have an Arduino project where I want to log current in a circuit and am using an AD236AN.
If I should use something other than an AD236, I'm open to suggestion.
The circuit is one following this tutorial:
http://www.vwlowen.co.uk/arduino/current/current.htm
I tried contacting the author and banged my head on the desk the last few days.
Goal:
Make a kit I can insert between a device's PS and the device that will measure the device's current consumption via Arduino and send the data to a logging server.
I'd prefer to not have to worry about the tested circuit's supply voltage and instead worry about voltage drop across the shunt to calculate current.
Parts:
- Arduino Uno
- AD236AN
- .01Ω current sense resistor
- 100 nF ceramic cap
- 28 turn Variable resistor
- Testing load source
I tried this out on 2 different circuits because even 2 LEDs don't have much current draw which means the drop across the shunt is very low. (<2mV)
With the .01Ω shunt I (attempt to) use a 100x gain meaning the voltage across the shunt with gain100 should be the current of the circuit it's plugged into.
(The writeup uses gain of 10 and then multiplies that by 10 in the Arduino code)
The 2 circuits differ in that 1 uses a flashlight bulb(2.4V) and 2 D cells for its power source
and the other uses 2 parallel LEDs powered by the Arduino 5V with a 110Ω resistor.
Problem:
I cannot get the gain to follow the datasheet.
for gain 100, I should use 1.02KΩ for R1 but instead it comes out to ~gain 200.
If I instead double up and use 2020Ω it comes out right?
(I got that from this example sheet of basic InAmps: pg19 http://www.analog.com/static/imported-files/application_notes/AN-244.pdf)
I know what you're thinking:
"Who cares? Use the working resistance."
"Who cares? Use the working resistance."
I'd rather know what is wrong in this circuit, and I want it to be accurate.
(It bounces back and forth ~5mA right now and it should really be steady)
Testing:
I'm using a DMM to verify the current draw in-line between the circuit and ground.
I only run the LED *or* lamp circuits, never both.
Thanks in advance:
I'm sorry to have to post, I really don't like to and prefer to rely on searching/Google, but it's been days and I need help.
Thanks for looking and/or helping. (And sorry for TL;DR)
(It bounces back and forth ~5mA right now and it should really be steady)
Testing:
I'm using a DMM to verify the current draw in-line between the circuit and ground.
I only run the LED *or* lamp circuits, never both.
Thanks in advance:
I'm sorry to have to post, I really don't like to and prefer to rely on searching/Google, but it's been days and I need help.
Thanks for looking and/or helping. (And sorry for TL;DR)