Monday, June 17, 2019

Main spacecraft connector and patch panel finished, accelerometer simulator plugged in

Main connector

All connections between the spacecraft and the Apollo Guidance Computer take place through the main connector (A51). This has 360 pins, six rows high and 60 columns wide. The DSKY itself connects through A51, which made this a priority to implement.

As I detailed in an earlier post, this is a labor intensive cleaning process but finally we had all of them ready for a male connector to be inserted. We had designed an aluminum plate to hold the 360 Malco mini-wasp pins and to position a printed circuit board we designed atop it. The pins were soldered to the PCB and the far end held eight HD50 connectors (familiar to those who used these as SCSI cables).
Connector attached to AGC carrying 360 signals out for our access
The connector was inserted with a partial population of pins - those we needed for our demonstrations. We will finish installing the remaining pins later. The eight cables were run from the PCB out to the patch panels that gave us the same six row by 60 column array as banana plug receptacles. We used this to hook up the DSKY and simulated switches and other spacecraft systems.

Accelerometer simulator developed

Marc designed an Arduino based module that would simulate the accelerometers of the LM spacecraft. These Pendulous Integrating Pulse Accelerometers (PIPAs) swing a small pendulum back and forth kicked by three pulses in one direction followed by three in the other. When no external acceleration exists, the PIPA outputs a steady stream of three positive then three negative pulses.

PIPA simulator plugged into patch panel
The AGC software checks for this pattern and throws up a Program alarm (212) if they are not present, since that means the inertial navigation and digital autopilot functions can't be performed. Marc's device would deliver this pulse stream into the appropriate pins of the A51 connector, through our patch panel. He also designed it to allow him to add extra pulses in either direction to reflect acceleration of the LM.

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