ECG with Bluetooth data transmission to smartphone - Page 1
Forum section: electronics / projects

author: brutester
author_rank: Contributor
timestamp: April 15, 2015, 06:51:01 am
content: Hi,Last year I've made this as a bachelors thesis project. I've build a prototype board (hand soldered it) and it is working very nice.The device is runing on 4.1V Li-Ion battery for safty (no mains decoupling required). It also gives mobility of the user.I've made a 50Hz notch and 0.2 Hz high-pass filter so you can plug the analog output into an osciloscope, but in reality you can remove them and have all digital filtering (you get same signal into ADC input as Dave in EEVBlog #660).The mcu source is not nice and clean. Today I'll do it with low-level MCU configuration, but hey it was like 2 day job.The algorithm I've implemented for ecg_filtering is removing 50Hz hum and baseline drift. To remove 60Hz hum you need to Change the Fs constant to 300Hz and sample size to 5 (by changing BSIZE=5).The android app is very simple. This is an EE blog so no need to go into that.

author: Arseneau
author_rank: Newbie
timestamp: April 15, 2015, 11:39:05 pm
content: Hey, very nice so far.Can't wait to see the final implementation.

author: moffy
author_rank: Super Contributor
timestamp: April 15, 2015, 11:49:13 pm
content: Pretty cool. Sounds like a good idea too. What is your current consumption like for the battery?

author: brutester
author_rank: Contributor
timestamp: April 16, 2015, 03:25:29 am
content: Quote from: moffy on April 15, 2015, 11:49:13 pmMax consumption is 53.1mAAnalog circuit is 13 mAMCU 5.1mABluetooth module on standby - 9.5 mABluetooth module when transmiting - 35 mAAs I said - this can be optimized a lot by:1. Simplify analog circuit to the instrumental amplifier and the first two OP amps. Ina333 uses 150uA (if I remember correctly). There are many low-power OPamps, but the OPA4322 I used was the cheapest 20MHz BW I could get my hand on2. MCU can be configured on lower frequency, should use timer interrupts for wake up, changing it to the new MSP432 core, etc.. it can be lowered by 1/2 or more. Btw, MSP432 has a 14 bit SAR ADC which will give better details.3. There are Bluetooth 4.0 LE modules that use much less power than the microchip one I've used. Original idea was to use PAN1323 by TI, but I had to write my own bluetooth stack. I was in a hurry so I used that microchip UART based module (which is very nice for small projects).

author: babysitter
author_rank: Frequent Contributor
timestamp: April 16, 2015, 05:55:11 am
content: Nice! You might consider the following, too:Use a (resettable) fuse for the battery, in case you short out something, which is easy during breadboarding, it might prevent some nasty burns, especially if worn to the body.Use a single connector for charging and attaching electrodes. Make cables that do only one job. This way you can prevent having a mains-powered charger bridged thru your device to your skin, which might be uncool in case the charger fails.Use a single connector for charging and attaching electrodes. Make cables that do only one job. This way you can prevent having a mains-powered charger bridged thru your device to your skin, which might be uncool in case the charger fails.For simpler use, you can put a bridge in the electrode connector that replaces the power switch.That way the device starts up when you connect the electrodes. Without electrodes, its unnecessary to deplete the battery, and its one less step for the preparations.