Week 28 - lglik/Portfolio GitHub Wiki

03/18/19 - 03/22/19

Day One:

Today I completed and installed the last of the eight ground wires. I am now done with the new wiring system which is nice after working on it for so long. A lot of testing and checking will still need to be done before the new batteries are actually installed. I started said testing today. Blake and I referenced the schematic and used multi meters to do continuity tests. The project is still turned off so we only tested the system in the mode where batteries 3 and 4 are being used and 1 and 2 are charging. With Mr. Harlow's permission, I plugged in the project and worked on changing the code to send signals in a way that makes sense for the new wiring. There are still no batteries installed since they should not be until the wiring is tested with the relays switching.

Day Two:

Mr. Harlow suggested an additional way to test that the wiring was working without actually plugging in the batteries. He pointed out that the batteries have no fuses built into them so it would be pretty bad if they shorted out, but that power supplies have fuses so it would not be very bad for them if they shorted. Therefore, I got two power supplies and plugged them in where one of the pairs of batteries would go. To further minimize the risk, I unplugged all of the boards the batteries would power except for one or two. I plugged in the power supplies, turned on the project, and told it to charge the pair of batteries that were not there and use the two power supplies. This test was successful and the boards that were plugged in were powered and nothing shorted out since the fuses did not blow. I repeated this test again a second time by plugging in the power supplies to where the other pair of batteries would go. This test was also successful.

Two power supplies connected to where two of the batteries will be connected.

Day Three:

Today, I went on a field trip with a few other students and teachers to the Montecito Bank and Trust Data Center. We were toured around the facility and then given a very detailed run through on how their system works. Hearing about out the physical, electrical, and digital security was fascinating. All of the employees there were very nice and happy to tell us about what they are working on and answer our many questions. Though I know most data centers won't be nearly as well funded and secure as a bank's, the tour certainly piqued my curiosity about computer security, server management, and IT work. This tour took most of the morning, so I was not able to work on my project today. The tour was definitely worth the lost time though.

Day Four:

Today I made and installed new wires and connectors on the batteries so that each battery will be able to connect to the circuit individually. Mr. Harlow suggested that as a next step in my testing I should try to charge two of the batteries. I placed all four batteries in the project but I only plugged one pair in. I then powered up the project and told it to use the pair that was not plugged in and charge the other pair that is connected. I then used a multi meter to confirm that the batteries were actually being charged. At this point I was finally able to install and connect all of the batteries. At first, everything seemed to work correctly. The batteries not being used each charged using their own bank and the other power was able to power the project. However, when turned off and unplugged my project at the end of the day, the electromagnets and motor controllers continued to be powered by the batteries. This was not an issue caused by a mistake when putting in the wiring but an issue with the design of my system. I did not make it so that the load could be disconnected from ALL of the batteries at once.

A single pair of batteries plugged in and charging for testing.

Day Five:

First, I made a new schematic that would allow all the batteries to be disconnected. I added in two more relays that intercept the load wires before they get to the project. The relays will be setup such that the load will be normally open so that when the pi loses power, the battteries will be disconnected from the load. I finished up the schematic and printed it out using the copy machine. I attached the two new relays to previouysly drilled locations on the mounts for the batteries. More signal wires are needed for the two new relays and those signal wires need to carry a different signal than the rest of the signal wires. Conveniently, I I was able to move the two wires that I had programmed to be the same signal as the third wire and attach those two wires to the two new relays. I still had to make new wires for the newly bereft relays. I cut 4 new wires (2 sets of power and ground) to length, stripped them, soldered them into the board with the other signal wires.