That's an absolutely phenomenal trace... Obviously he's working under somewhat idealized noise conditions (as he described), but that trace is _cleaner_ than what we get out of the portable ECG monitors we carry in the back of ambulances (it also has much higher resolution). These are monitors have a price tag that you'd be more familiar with on a new car...
Don't get me wrong, I'm well aware that there's a big gap between some wires in a breadboard and a ruggedized, battle tested 12-lead. I'm not complaining about the cost of our Lifepacks; rather I'm ust blown away at how great that trace looks with such rudimentary equipment.
I'm gonna have to 'borrow' some electrodes from the station and give this a shot myself...
Hi, I'm glad to hear that, I'll be happy to help if you plan to build one!
As for the idealized conditions, if I gently pass my finger on my laptop's aluminum case I can feel the 50hz hum, so that is why I have to unplug it to get that signal, it may be a laptop's issue. I will check with a desktop and post my results.
50hz is pretty easy to knock our with a simple RC low pass filter. That should make a difference but it will probably attenuate the signal so you will need an instrumentation amp.
2 hours later... Ahh commercial grade design and massive BOM.
Thanks! I am using an instrumentation amp indeed. As for the 50hz, I think I'm getting that noise just because my laptop is not grounded properly, no biggie
I had a Chinese clone Lenovo charger a while ago. There was 50v floating AC on the chassis when supposedly open circuit (!). Zapped myself on any metal part I touched.
Fake one was dismantled for study and appeared to be missing most of the components. Tracing the circuit found a 1k resistor between live/hot and the ring on the PSU connector (laptop chassis DC ground). Turns out I was basically turning it into a voltage divider by touching it and was a the mercy of my quite high skin resistance :)
Replaced with a genuine Lenovo one immediately resulting in no random minor electrocutions!
Yes i noticed that too, I thought it could be because I put the leads where ever I felt like.
I am using 3 electrodes, the reference one (ground), was on my right thigh, the other two were, one where my right chest meets the shoulder and the other one on my left side at the level where the floating ribs are...
I placed them in non standard positions so that is why i may be getting funny values... But I agree that lower lobe is not in any ECG I have checked so far... I may go to the doctor to double check..
That's close enough to the standard Lead II. A biphasic T wave in that lead is technically abnormal, but there are a number of benign causes. Certainly wouldn't hurt to check in with your doctor though (and you get to tell him a cool story of how you discovered it)
Hey! Thanks for letting me know! I'll try to get a real ECG as soon as I can... I hope that negative lobe is just an artifact :) Thanks again, and if you need help building one please let me know I'll be happy to help!
I am assuming you do the A/D conversion with the electronic board, and then treat the digital signal with the Arduino?
How difficult would it be to wire your A/D conversion unit to do USB? Then any laptop, or even a smart phone could do the UI part. Or am I missing something?
The arduino has an ADC conversor and sends it with no posprocessing at all to the PC. This could be easily used with a smart phone indeed, in fact that is my next step :)
I'm good enough to follow along a diagram and build stuff I find online, but have no real clue as to the electronics.
Given I have a neglected arduino kicking about and a paramedic I could probably get some electrodes from how far removed is this kit from knocking up a very basic 'brain controller'?
I've often fancied feeding some 'thoughts' into Ableton for some synth tweaking fun.
[edit] thought I should actually do some searching on the subject and I just found the openEEG project which has some info in that direction.
I would DEFINITELY use opto-isolators (my EEG BCI had them) and would always run the ECG on a laptop with its AC adapter _unplugged_. Do you really want to risk even a small chance of electrocution?
21 comments
[ 6.6 ms ] story [ 76.7 ms ] threadDon't get me wrong, I'm well aware that there's a big gap between some wires in a breadboard and a ruggedized, battle tested 12-lead. I'm not complaining about the cost of our Lifepacks; rather I'm ust blown away at how great that trace looks with such rudimentary equipment.
I'm gonna have to 'borrow' some electrodes from the station and give this a shot myself...
As for the idealized conditions, if I gently pass my finger on my laptop's aluminum case I can feel the 50hz hum, so that is why I have to unplug it to get that signal, it may be a laptop's issue. I will check with a desktop and post my results.
2 hours later... Ahh commercial grade design and massive BOM.
Great work at keeping it simple :)
I had a Chinese clone Lenovo charger a while ago. There was 50v floating AC on the chassis when supposedly open circuit (!). Zapped myself on any metal part I touched.
Fake one was dismantled for study and appeared to be missing most of the components. Tracing the circuit found a 1k resistor between live/hot and the ring on the PSU connector (laptop chassis DC ground). Turns out I was basically turning it into a voltage divider by touching it and was a the mercy of my quite high skin resistance :)
Replaced with a genuine Lenovo one immediately resulting in no random minor electrocutions!
I am using 3 electrodes, the reference one (ground), was on my right thigh, the other two were, one where my right chest meets the shoulder and the other one on my left side at the level where the floating ribs are...
I placed them in non standard positions so that is why i may be getting funny values... But I agree that lower lobe is not in any ECG I have checked so far... I may go to the doctor to double check..
I built a pulse oximeter as my final year project at university and have been rather obsessed with medical electronics since.
I've always wondered if it's possible to build your own ultrasound sensor. Rather complicated devices though.
How difficult would it be to wire your A/D conversion unit to do USB? Then any laptop, or even a smart phone could do the UI part. Or am I missing something?
http://web.eecs.umich.edu/~prabal/projects/hijack/
Given I have a neglected arduino kicking about and a paramedic I could probably get some electrodes from how far removed is this kit from knocking up a very basic 'brain controller'?
I've often fancied feeding some 'thoughts' into Ableton for some synth tweaking fun.
[edit] thought I should actually do some searching on the subject and I just found the openEEG project which has some info in that direction.