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- The Controls Leaderboard takes in a 12V line from the supplemental battery (through POW_2ND_CONN). This is a small 12V battery meant mainly for the startup of our boards; once the big main HV battery pack is up and runningdeemed safe by BPS, all low-voltage power will switch to that.
- Note that there are 6 positions on the ignition switch, where corresponding pairs are connected as the ignition switch is rotated (1 and 7 are connected at the same time, 2 and 8 as well, 3 and 9, etc.)
- Diagonally opposite positions of our ignition switch are connected up at the same time. Note that it's essentially the same as two separate switches being "synced up", and this model is AKA a double pole switch.
- The bottom half of the ignition switch (pins 1 through 6) facilitates the LV on/off signal. Depending on the position of the Ignition Switch, this 12V will be routed to BPS_PWR_OUT. This connector is wired to the Power Board (formerly known as the Secondary Power Board). The idea is that we send 12V across this line once the ignition switch is turned to the appropriate position to signal that we would like power to be provided to our Low Voltage (LV) systemsPreviously this was used to power BPS during startup to determine the conditions of the battery pack; however, now it's used as a signal for the Power Board to connect the Supplemental Batteries to the Fusebox, which will power all LV boards.
- As you can see in the diagram, BPS_PWR_OUT receives 12V at any position other than position 6 (same as position 12). This is because that is our off position, and in any other position we need the car to receive LV power.
- In a state where the HV battery has been deemed unsafe, this signal is still necessary to provide the enable signal to the Power Board
- As you can see in the diagram, BPS_PWR_OUT receives 12V at any position other than position 6 (same as position 12). This is because that is our off position, and in any other position we need the car to receive LV power.
- The top half of the ignition switch (pins 7 through 12) provides a digital signal to two pins on the Controls leaderboard (IGN1 and IGN2). As you can see in the diagram, each position labeled.
- Pos. 12 is OFF, and this corresponds with pos. 6 (since both connect to nothing)
- Pos. 11 is LV. This is allocated a position so that it only turns on LV and nothing else. In actuality, all the other positions will also turn on LV as well, but they will turn on other things too.
- Pos. 10 is ARR_ON. This is hooked up to the IGN_1 pin on the Controls Leaderboard in order to tell Controls to begin the Array Precharge sequence.
- Pos. 9 is MOT_ON. This is hooked up to the IGN_2 pin on the Controls Leaderboard in order to tell Controls to begin the Motor Precharge sequence.
- Any further positions (pos. 8 and 7) are also hooked up to IGN_2.
- Note that the intent of the Ignition Switch control is intends to make the positions cumulative. For example, when clicking from LV → ARR_ON, the low voltage systems will continue to remain active in the ARR_ON position. Furthermore, when clicking from ARR_ON → MOT_ON, both the array and the low voltage systems will continue to remain active in the MOT_ON position
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Photocouplers allow for logic to be done across two power domains, as seen here. If a photocoupler has current, then the transistor on the other side allows current to conduct, creating a short circuit. On the other side of the photocouplers, is a GPIO input that is pulled up to 3.3V (3V power domain). The MCU reads HIGH if the photocoupler has no current going through it since there is an open circuit to ground. Once the photocoupler receives current, it creates the short circuit meaning the node on which the GPIO input sits on is now GND and the MCU reads LOW.
Photocouplers also provide input isolation, which is necessary for when the Controls Leader board will be using the 12V from the Fusebox while reading 12V signals from the Ignition switch.
The photocoupler is also referred to as an optocoupler , or an opto-isolator.
Precharge
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The following are the steps in the sequence of the rotary switch. The first step is when the rotary switch is turned clockwise all the way from the perspective of the user.
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The HV Plus/Minus BPS Contactors tells tell Controls to close Motor Controller Precharge-Bypass Contactor. The Array BPS Contactor tells Controls to close Array Precharge-Bypass Contactor.
The least significant bit (bit 0) is associated with the Array BPS Contactor, and the bit 1 and 2 are associated with the HV Minus and Plus Contactors. The HV Minus and Plus Contactors are grouped together because Controls requires require both to close the Motor Controller PBC. It is important to note that HV Plus and Minus Contactors are two separate contactors that BPS owns. Because Controls logically ANDs HV Plus and HV Minus Contactors, they acknowledge it as a single entity, which it is not.
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When we switch to a state, such as Array or Motor, we send a CAN message to BPS on CarCAN to tell them that we are wanting want array to be charged. We wait and listen for a message back once they have confirmed that is true. We do this so that we do not use the array or motor in our code until they have been charged.
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I would like there to be a diagram that shows how all contactors Contactors are set up.