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Topic: Help with AD8232 and portability (Read 113 times) previous topic - next topic

JediEmma

Hi, I've recently taken up a project with arduino using the AD8232 heart ecg chip breakout board from SparkFun. So far so good, I have my project working exactly how I want it, it detects my pulse, everythings working. There's just one problem, I want my project to be battery powered, and so far my project works fine when powered from a computers usb port, but not from a mains usb adapter or a battery source. The AD8232 stops working completely and only shows some signs of life when I touch the arduino on certain pins... I'm at a loss after searching for hours on google regarding my issue, I feel it has something to do with the way my power is set up but I'm not sure. How I have it set up is this:

I'm using Arduino UNO, I have a piezo wired to pins 7, 6 and 5 which is on it's own breakout with the necessary resistors.
I have the AD8232 wired to the 3.3v and Gnd pins of the UNO, and the signal is wired to A0 and the LO lines are connected to pins 10 and 11.

As I said it works fine when plugged into a computers usb port. I don't really understand the difference, I tried running it off a mains adapter connected to the barrel port at 12v, same result as the mains usb adapter. Ideally I want this to run from a battery bank off of usb. I feel like I'm just missing something to be honest but I can't figure out what it is. Any help or advice or guidance you can give me will be great and much appreciated, thanks in advance, Emma.

pylon

Please explain what that piezo is. Is it a piezo buzzer or a piezo electric sensor or anything else? Please provide a link to this device.

Also explain how you detect if the AD8232 is working or not if you don't have a computer attached. Especially explain what these "signs of life" are if you touch the Arduino pins and what pins exactly you touch for this.

JediEmma

the piezo is a buzzer, simply beeps and alarms according to heart rate. I have managed to get this working on a battery bank which I'm assuming implements it's usb ports same as a computer does. Unlike my mains usb charger which is obviously skipping some steps. So I guess even though my question is unsolved I have solved the problem, I'd still like to know why the battery bank and computer usb ports work and the mains usb charger doesn't... hmmm

TomGeorge

#3
Oct 13, 2017, 12:32 am Last Edit: Oct 13, 2017, 12:38 am by TomGeorge
Hi,
The mains adapter is a switch mode power supply, it does produce electrical noise.
Including some mains born noise.
You are using a device that is susceptible to electrical noise, that is how it gets the ECG signal.

The main purpose of your adapter is probably as a charger, so noise suppression to the degree of ECG usage is pushing it design limits a bit.

Your PC and bank, both have similar power supplies but are designed to be as noise free as possible.

When in fault mode, does the heart beat LED on the breakout pcb blink with heartbeat?

Tom.. :)
PS. As this is a device connected to the human body and detecting currents that flow via the heart, a battery bank is the safest way to use it.

https://www.sparkfun.com/products/12650
Everything runs on smoke, let the smoke out, it stops running....

JediEmma

#4
Oct 13, 2017, 03:00 pm Last Edit: Oct 13, 2017, 03:06 pm by JediEmma
Hi,
The mains adapter is a switch mode power supply, it does produce electrical noise.
Including some mains born noise.
You are using a device that is susceptible to electrical noise, that is how it gets the ECG signal.

The main purpose of your adapter is probably as a charger, so noise suppression to the degree of ECG usage is pushing it design limits a bit.

Your PC and bank, both have similar power supplies but are designed to be as noise free as possible.

When in fault mode, does the heart beat LED on the breakout pcb blink with heartbeat?

Tom.. :)
PS. As this is a device connected to the human body and detecting currents that flow via the heart, a battery bank is the safest way to use it.

https://www.sparkfun.com/products/12650

Thank you so much for your very informative reply, I guess you're right about the mains charger, although when powered by the mains charger it turns on, but the ecg outputs nothing and its led stayed off all the time, except for when I touched certain pins on the arduino and then it would light up but it would stay lit, still outputing nothing, that's why I questioned the charger... the device works great on the battery bank and from my computer ports so I just use the computer ports as mains supply lol
I wonder if there is a usb charger device out there that would be suitable for my project... hmm
Also maybe theres a way I could add circuitry to my project that would produce the same noise levelling as you describe so that it works from any usb port?!

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