Flowcode programming

kokos said:

Thanks Gobbledok i will build and test the circuit you posted above with IR LED 940nm and a photodiode.

Thanks
kokos

Click to expand...

Gobbledok said:

Cool let me know how you go and we can troubleshoot from there

Click to expand...

kokos said:

Hi again

i constracted the circuit you posted above and placed the IR LED oposite to photodiode. when the power is on the LED is on and when i place my finger between the sensors the led turns off and i am trying to adjust the trimmer but i cant see any pulse. i also increased and decreased the values of R1 and R2 but still icant see any pulse. do you think that the signal need to be amplified first?

Thanks

Click to expand...

Gobbledok said:

You may need to amplify the signal first. I really have no idea how the IR sensor will react with your pulse. It all depends on the difference of light when a heart beat occurs.

Are you able to crudely measure with a multimeter the voltage at the top of R1 when the meter is on your finger?

Click to expand...

kokos said:

yeah i can do that. what voltage i should expect when my finger is between the sensors?

Click to expand...

Gobbledok said:

I have no idea. I don't know what to expect from the sensor.

Just reading about it some people are saying that you have to use a red LED and an IR LED to measure pulse. Is it possible to measure pulse using the sensor this way? I was just going off what you had already done.

Click to expand...

kokos said:

yeah i saw that somewhere.they used a red led and an IR led but also with only an IR led it can measure the pulse. do you know if i must use a current to voltage converter first after to amplify the signal and after to use the circuit that you posted? i am kind of confused here..

Click to expand...

sharilewis said:

I've been meaning to have a play with flowcode for a while and so thought this would be a good time. I implemented your code without the LCD stuff but with a few changes. I've looked at the C code produced and it appears to be correct.

Click to expand...

Pommie said:

That appears to be a direct quote of my post (#15). What was the purpose of doing that?

Mike.

Click to expand...

Gobbledok said:

As it is you won't need a current to voltage converter.

A photodiode will increase its current in the presence of light. That will create a voltage drop across R1 which is what the comparator reads.

I really have no idea how sensitive your sensor needs to be, or what the photodiode on the other side of your finger sees. If the difference between pulse and no pulse is tiny, then it is only a tiny voltage change you are trying to detect.

If someone else says you need a current to voltage converter, they might know more about using this sort of sensor than me.

Click to expand...