ECG

[pritch1]

Hi i am a final year design technology student and am in the process of designing a bicycle heart rate monitor and im looking for some help. To forfill the project i am looking for a heart rate monitor which which uses only 2 inputs on the thumbs. I have experimented with an ina114 intrementation amplifier and have used a number of different gains without sucess, does any one know of any other possible solutions, im sure it should be possible as i have ridden exercise bikes in the past with 2 thumb contacts but can not seem to find any information on them. thanks for any information.

 

[stevez]

Whatever you do be sure you understand the established safe limits of current and voltage that the human body can be exposed to - and that you carefully review the various failure modes to be sure these limits aren't ever exceeded. Under the right conditions it doesn't take a lot of current/voltage to hurt someone.

 

[JimB]

Do a search for "Pulse Oxymeter". The main function of this is to measure blood oxygen saturation, but I believe it will also give pulse rate.
It works by shining beams of (infra red?) light through a finger and measuring the absorbtion.
I think this is more likely to give success than looking for a microvolt electrical signal.

JimB

 

[stevez]

Pulse oximeter came to mind when I first looked at this however about 1/3 of the cardio equipment at my gym has "electrodes" on the handles. You hold the handles and get your heart rate if your hands aren't really dry. The level of signal is likely similar to what you might get with a chest strap. I understand that the big challenge is sorting out the intelligence (that which signals a heartbeat) from all of the other noise, drift resulting from changes in conductivity of the electrodes, etc.

 

[pritch1]

yea i had looked at using infa red but it was really the small voltage i wanted to pick up it will be running of a 9 volt batters so cant see any problems with voltage and current correct me if im wrong. the data should hopefully be fed into a pic micro chip and the signal clipped to get the heart rate.

 

[Gorgon]

yea i had looked at using infa red but it was really the small voltage i wanted to pick up it will be running of a 9 volt batters so cant see any problems with voltage and current correct me if im wrong. the data should hopefully be fed into a pic micro chip and the signal clipped to get the heart rate.

If you want to use the electric impulses I don't think the fingers is of much use. You either use pressure or light to measure the pulse here.
The electric activity is around the heart, and even a 9v difference through your heart at some mA's may do great harm.

Take care. Understand before doing!

TOK

 

[Klaus]

yea i had looked at using infa red but it was really the small voltage i wanted to pick up it will be running of a 9 volt batters so cant see any problems with voltage and current correct me if im wrong. the data should hopefully be fed into a pic micro chip and the signal clipped to get the heart rate.

We are using commercial EMG equipment and you can believe me that there are people that can feel 9V from the electrodes onto sound skin. This only happens when the tiny leads to the preamp go faulty though. Still, the subjects report an uncomfortable shock but I never can feel it myself ( thick skin .
9V battery power onto damaged skin could be nasty.

I wish you luck with the thumb pick up, this sounds a bit of a challenge to me.
Klaus

 

[pritch1]

thanks for the help i will check up on the voltage then still struggling with the thumb pick ups all i seem to get is mains interfeerance on the scope but i have a really high gain now and still no signal :S