SparkFun Forums

[Clemen89]

Hello,

I'm desperate, I don't know what is the problem. I'll explain all.

I have bought 4 devices (https://www.sparkfun.com/products/12650), medical electrodes and these wires https://www.sparkfun.com/products/12970. I've got Arduino UNO and the software required.

I have powered the devices with 3.3V and GND(from Arduino), I connect all the wires like a Hookup Guide (https://learn.sparkfun.com/tutorials/ad ... 1441193009):

Output -> analog pin 0
LO- and LO+ --> Digital pin 10 and 11

And I have used the arduino code used in hookup guide, but I've always obtained this when I open serial plotter in Arduino software:



I connect the electrodes in my arm wrists and the RL signal in ankle.

I don't know why, any help please??

Thank you in advance.

Regards

[jremington]

The signal you see could be power line hum, which you expect from a improperly connected lead or bad ground connection.

Double check all connections -- it is best to solder wires rather than rely on breadboards.
Also check the power supply voltage at the monitor board to make sure it is 3.3V.

[Clemen89]

For god sake...

When you have said bad ground connection, you give me an idea. I disconnect the power cable of laptop, so the laptop is powered by battery right now, and the sensor works fine (facepalm).

I don't know why when I powered arduino with USB and the laptop is connected to power cable isn't works..

Thank you very much!

[Ross Robotics]

I don't know why when I powered arduino with USB and the laptop is connected to power cable isn't works..

It's called a Ground Loop. Google it to find more info.

[jremington]

For sensitive circuitry like that and ESPECIALLY for anything connected to the human body, battery operated devices are a must. Sparkfun should have a caution to this effect right up front on that product page.

Compared to consumer electronics, medical electronics have to pass several additional levels of safety standards and certification.