Schematics
The schematics were designed in Orcad. Let us discuss what each schematic board does.
This board has the 2 * A4988 stepper drivers for the motors. It has the current control feature using trimmer resistors. Output Pins to the motors and input pin from the raspberry pi and the power supply of 12V. More on the full components list here
The IMU board is a fairly simple board. It has just the MPU-9250 chip and a couple of resistors and capacitors. It has a power input of 3V3 and has I2C connection to the raspberry pi. Other output pins were also provided if required such as interrupt pin. The pins require pull up resistors and some, pull down resistors. More on the full components list here
The power board has 4 main sections. The first is the charging control unit. A 12V charger can be connected to the DC Jack to charge up the batteries. It uses a comparator to monitor the level of charge (Either full or not). It can also detect polarity switching and warn with an LED.
The second part following the charging unit is a high current 12V regulator to provide the motors sufficient and steady power supply. It uses an LM723 chip and some transistors to regulate the power. Input is 11-13 VDC and outputs steady 12V. Some of the large transistors were broken into separate boards to accomodate space.
The next part is a high current 5V regulator. Now, this is very import to have sufficient current and steady voltage. Because most of the components utilize a 5V level logic, including the raspberry pi. If current is not sufficient, it can cause a brownout. It uses LM7805 in tandem with an MJE2955 for increased current output. The regulator must have a heat sink attached to avoid it from getting too hot.
The last section is a 3V3 regulator to provide power to the IMU and any logic requiring 3V3 power supply including future additions. This doesn't require large power as it only powers small demanding chips. It uses LM3940 chip. More on the full components list here
SatRot - Taking everyone to space!!!