Soon after school let out Jesse started working on developing the relay system using a SunFounder 8 channel relay. He got the module from Frank Monforte before leaving for winter break. The relay works with Arduino UNO 2560 1280, ARM, PIC, AVR,
STM32 and Raspberry Pi. We will be using the PIC18F45K20 to operate the
relays. We need the relays to accurately read in the values from the MFC. In
total, we will need three relays for each MFC. The relays will be connected to the MFC system as show in the figure below
First, relay two and three must be closed and relay one must be open. Before
reading the voltages from the MFC, the ADC pin will build up charge over time
and this charge must be sent to ground before closing relay one to avoid false
positives. Second, relay one and three must be open and relay two must be
closed. Jesse needs to do this to read in the values before reading the MFC. This
step has to be done to make sure the MFC is not giving off any voltages when
relay three is open. The last step is to close relay one and two, and open relay
three. At this point the MFC system is can be read and logged. The figure
below shows his code.
At this point, the relay system is working with the DC power supply to take
in voltages. He is able to read the voltages after the relay has gone through the
cycle using a multimeter. The problem he has is that the voltages he’s sending are
not the same as the voltages he’s getting through the relays. After discussing the
problem with Frank, he told him that he needs to see if the relays have any internal
resistance. Jesse found out that they do. He is currently researching how to cancel
out the internal resistance. There are two options, either find a way to cancel out
the resistances or buy new relays that have smaller internal resistance.
Jesse needs the ADC in the PIC to convert the voltages into readable data for the
Raspberry Pi. As of now He is still having trouble with ADC conversation pro-
cesses. he’s gone over the data sheet several times and used previous labs but
something is still wrong with the processes. When he figures out the problem he
will be able to move on to the next step. He will then need to establish a Vref for
the MFC. He needs the Vref because the MFC only gives out small voltages and
will need a reference. He already created the Vref. All he need to do is add it into
the code. In the beginning, he was using a voltage divider to bring the 5V down
to 1.025V. After talking with Frank he advised me that it will not always be the
case. He now needs to get a voltage regulator to keep the reference voltage constant. He is looking at a few right now like the S-1172 Series and the PTH04000W
Omar has created a LAMP server on the Raspberry Pi. It can only be accessed from the local network. It needs to be able to connect to the Internet and a buying server space from a domain website could work. There was supposed to be any easy way to allow the Raspberry Pi to host the website, but Omar was not able to get it to work on campus and at his home, most likely because of the firewalls from each network. He has been learning HTML, some CSS, and PHP to create the website. He has the website able to read in a text file and display the contents. The text is not yet formatted but it is being worked on.
The next step is to connect the PIC to the RPi, the options available are USART, SPI, and I2C. Jesse is currently researching which option is best for us.