2.2 Voltage Conversion
The RAMBo has four rows of pins used to send and receive UART serial commands. However, the serial port on the Fusion 6000 syringe pump is an RS232, which sends and receives signals at a different voltage level than the RAMBo. To solve this problem, two RS232 to TTL converters are used (BC71075, NKC Electronics). The converters, shown in Figure 2, are built around a MAX232 chip, which uses a capacitive voltage generator to transform the 5V signal from the RAMBo into a 15V signal that the RS232 port can recognize . A more detailed schematic of the converters can be found in Figure A3 in the appendix.
These two converters connect two of the four rows of serial pins in the RAMBo to the two extruders. Hypothetically, if one were to add more extruders for builds that required additional printing materials, a third and fourth extruder could be added by purchasing two additional converters and using the remaining two serial pins.