Timeline for recording low frequeny using sound card
Current License: CC BY-SA 3.0
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| Jan 12, 2017 at 13:36 | comment | added | Isra | but wouldn't that mean that the -vcc and the +vcc for the opamps wont have the same "absolute value"....meaning, 2.5V isn't halfway between 0 and 9, will that cause problems with the opamps? | |
| Jan 12, 2017 at 13:32 | comment | added | Torbjorn V. | Arduino usually handles negative voltages OK. It will read as 0 though. You should also add a protection resistor between the signal output and the arduino. I would recomend that you use a 9V supply, but change the resistors which generate the voltage offset in your circuits to generate an offset @ ~2.5V. Switching out the topmost 100k resistor with a 260k resistor should do it. | |
| Jan 11, 2017 at 18:40 | comment | added | Isra | Yes I'm using 9V supply, but why didn't that show in the oscilloscope? Will connecting the output to a voltage divider to reduce the output value help? And in this case what happens to the negative voltages in this case? Will arduino just block them or what will it do? | |
| Jan 11, 2017 at 16:11 | comment | added | Torbjorn V. | If your Arduino is connected to the output of the circuit shown above, then the signal should be lifted to vary around 2.5 V. That is if the VCC connected to the voltage-divider for the virtual ground is +5V. I would make sure that the ground of the arduino is connected to the actual ground used in the circuit you referenced. If you are connecting +9V to the VCC for the virtual ground, then you will get a signal that varies around 4.5V, which might explain the clipping? | |
| Jan 11, 2017 at 6:44 | comment | added | Isra | here us a link to my circuit, do you think I should use the virtual ground as my ground for the oscilloscope? electronics.stackexchange.com/questions/277360/… | |
| Jan 11, 2017 at 6:17 | comment | added | Isra | I was just reading more on that, could it be because the voltage has negative values as well? I learnt that Arduino doesn't read negative voltages (I thought it does, converting the (0 to 5V)rang to (-2.5 to 2.5v). I'll add a capacitor to remove DC offset, does it have to have a specific value?...my heartbeat amplifier's circuit has an offset removing capacitor at it's first stage (it's a 3 stage amplification and filtering circuit). | |
| Jan 10, 2017 at 12:26 | comment | added | Torbjorn V. | There are a few things you might want to check: Does the arduino and the heartbeat-monitor measure the voltage relative to the same ground-potential? Is your oscilloscope set in DC or AC-mode? If AC-mode, then the signal might have an amplitude of 0.3V, but the offset might be larger than that, resulting in a signal outside 5V. In this case, connect the heartrate-monitor to the Arduino through a high-pass-filter configured to offset the signal so that it varies around VCC/2. Have you tried to use a voltage divider to bring the voltage into a range that the arduino can measure? | |
| Jan 9, 2017 at 7:05 | comment | added | Isra | Yes, I did that as a first stage and it was somewhat working, but my adviser doesn't wan't the ADC's manipulation of the amplitude, the normal heartbeat amplitude was 0.3V on the oscilloscope, but when we use arduino, the amplitude is higher, and sometimes it gets clipped at the top (even though the input is <5V). He wants to try the audio jack and see if we got better results. | |
| Jan 8, 2017 at 13:43 | history | answered | Torbjorn V. | CC BY-SA 3.0 |