Analog Crosstalk on RPI Expansion HAT
lasshee 2020-05-26 03:08:55 1604 Views4 Replies Hi!
I am using the IO Expansion HAT for PiZero SKU:DFR0604
Together with three Capacitive Soil sensors SKU:SEN0193
On a Raspberry Pi 3B+
And I have some problems.
Firstly, the Wiki speaks of calibration values between 260 and 520, whereas I am getting readings between 1900(placed in water) and 3500(out in the air). The ADC in DFR0604 is 12 bit which should give me values between 0 and 4000. It seems I am not getting the full resolution which is a shame.
Second and much more annoying, when I put the sensor connected to A0 into water, the signal changes on sensor A1 also. In the image I have plotted A0 in blue and A1 in yellow. The same happens between A3 and A2.
I have measured the voltage between ground and VCC on the sensors and it seems to be stable at 2.97V.
As it is I cannot use more than one sensor without having a lot of noise between the sensors? Any tips for what I can try? Are SKU:DFR0604 and SKU:SEN0193 even supposed to work together?
I am using the IO Expansion HAT for PiZero SKU:DFR0604
Together with three Capacitive Soil sensors SKU:SEN0193
On a Raspberry Pi 3B+
And I have some problems.
Firstly, the Wiki speaks of calibration values between 260 and 520, whereas I am getting readings between 1900(placed in water) and 3500(out in the air). The ADC in DFR0604 is 12 bit which should give me values between 0 and 4000. It seems I am not getting the full resolution which is a shame.
Second and much more annoying, when I put the sensor connected to A0 into water, the signal changes on sensor A1 also. In the image I have plotted A0 in blue and A1 in yellow. The same happens between A3 and A2.
I have measured the voltage between ground and VCC on the sensors and it seems to be stable at 2.97V.
As it is I cannot use more than one sensor without having a lot of noise between the sensors? Any tips for what I can try? Are SKU:DFR0604 and SKU:SEN0193 even supposed to work together?
2020-05-28 10:20:16 
Of couse you can. But you have to connect analog singal line to A0~A4. 309330066
Of couse you can. But you have to connect analog singal line to A0~A4. 309330066 2020-05-26 17:31:51 Thanks for the quick answer!
The DFR0504 seem to require 5V, could I power those using the PWM V+ and GRND on the DFR0604? lasshee
The DFR0504 seem to require 5V, could I power those using the PWM V+ and GRND on the DFR0604?
lasshee 2020-05-26 15:52:29 Hi,
Firstly, In the wiki of SEN0193, the main control board used is UNO R3, the ADC in UNO R3 is 10-bit, values should between 0 and 1024. Beacause the voltage of UNO R3 is 5V and sensor feed back voltage is 0~3V, the value of SEN0193 is between 260 and 520. So the value you measured on the DFR0604 is between 1900 and 3500.
Second, The situation you mentioned is because there is no ground shielding between the analog interfaces. If you have 3 sensors, You can solve this problem with two DFR0504. 309330066
Firstly, In the wiki of SEN0193, the main control board used is UNO R3, the ADC in UNO R3 is 10-bit, values should between 0 and 1024. Beacause the voltage of UNO R3 is 5V and sensor feed back voltage is 0~3V, the value of SEN0193 is between 260 and 520. So the value you measured on the DFR0604 is between 1900 and 3500.
Second, The situation you mentioned is because there is no ground shielding between the analog interfaces. If you have 3 sensors, You can solve this problem with two DFR0504.
309330066 