Virtual Lab Project: PCB Design

The objective of the Virtual Lab project is to allow users to make measurements and observations using the online interface of the Red Pitaya, where the Red Pitaya is connected to a circuit. Read more about our journey through doing this project here, and click here, to explore on the finished Virtual Lab. This knowledge item goes further in depth about how we had planned to use a printed circuit board (PCB) in our project.

The circuit that is used in particular is a band-pass filter, using operational amplifiers, capacitors and resistors, the circuit that was designed can be seen in the schematic below, and as well as the calculations of the cut-off frequencies and the pass-band gain.

The purpose of this filter is to allow an input signal with a frequency within the range of the 2 cut-off frequencies to pass through, in this case a frequency within the range of 2.341kHz to 1.421MHz, any signals with a frequency out of the range are not able to pass through. The filter also provides a gain, both the cascaded low pass filter and high pass filter have a gain of 2, so the overall gain provided by the filter is 4, so the voltage of the initial input signal is therefore multiplied by 4.

Moving onto the design of the PCB for the circuit, using DesignSpark PCB, the first step was to create the schematic design. In order to do this, using the library, I selected the appropriate components for the circuit and arranged them on the grid. Here, I followed the connection of our design and connected the components accoridingly. The completed schematic design is as seen in the picture below.

Now in order to obtain the PCB, using the 'Translate to PCB' function in the software, after entering the values and details desired for our project, we were swiftly given the PCB file for our circuit. As you can see below, we chose to use a 2 layer PCB, arranging the 5 header pins to be beside one another to ensure a neat arrangement, and spaced out the two IC chips from one another. 

In order to get this fabricated, or any PCB in general, you would usually have to provide the Gerber files. Clicking on the 'Manufacturing Plots' which can be found under the Output menu. After checking that the settings were what we required, clicking on Run, the files were then prepared. Thus sending the Gerber files for the PCB to be fabricated.

Obtaining the fabricated PCB, after testing the circuits initially on a breadboard, we transferred the components onto the PCB before soldering them. We came across a few problems with the PCB not being fabricated properly, and due to time constraint as mentioned in our Virtual Lab Project Journey, we had planned to use a stripboard instead, but in the end after that did not work as well, we stuck to using the breadboard, unable to further develop due to limited time. The files for both the schematic and PCB design are attached below for reference.

For further reference, listed below is the BOM of the components for the circuit: