In today’s example we are showcasing a simple carbon monoxide (CO) gas sensor monitor using the Pioneer board. The Figaro TSG 5042 gas sensor is used in this example to detect a range of 0-10,000 ppm.
Forum Post Attachments:
At the bottom of this post we are including the following items:
- Example Project Zip File
- Project Images
- Gas Sensor Datasheet
The user can download the example project at the bottom of this post. The project uses the following list of Creator Components:
- Opamp (x2)
- SAR ADC
The main.c firmware is included in the example project. Please review the commented sections for more details.
In this design the sensor will, when detecting the chemical, produce a very small electric current which needs to be converted to a output voltage by an op-amp/resistor combination. To accomplish this our example project uses an op-amp with a feedback resistor for the sensor current to voltage conversion. This is effectively a Trans-Impedance Amplifier (TIA).
In the project we will use a reference voltage for the op-amp and an ADC to read in the output voltage from the TIA.
After the voltage has been sampled the value will be sent out over the UART to be displayed using a hyperterminal software.
In the schematic layout there are a couple of items that may need to be defined:
TIA_Reference: The SAR ADC internal reference of 1.024V bypassed to the port P1.7 is connected to the opamp_buffer input P1.5
Gas_sensor_ground: The buffered output of the TIA_reference. The negative terminal of the gas sensor is connected to this terminal which is fed io the non-inverting input of the TIA opamp.
Gas_sensor_sense: The gas sensor positive input is connected to the negative input of the TIA opamp. The feedback resistor of 500k is connected between the inverting output and the output of the opamp, TIA_output.
In the video below we have output the values to an LCD shield.
You will need to connect a couple of items for this example. First you will need to connect the bypass resistor (R1 503k ohms) and capacitor (C1 22uF).
Next connect the UART P4.1 pin to the P12.6 pin on the PSoC 5LP header.
Test Your Project:
Connect the hardware to the Pioneer board including capacitor, resistor and sensor. Next connect the UART bridge to the PSoC 4 board. Launch the hyperterminal software to view the data received from the Pioneer board.
In the video below you see the example project being used to calculate carbon monoxide out the back of a motor cycle pipe. Careful, the video is a little loud and suffers from a mild case of motorcycle adrenaline shaky cam.
I hope this example can help you in your design.