Motivation

During my first 2 years on SRT, I worked on setting up sensors and control interfaces for testing our rocket engines. I worked closely with the data acquisition box pictured below. 

From working with it, I quickly found myself needing to change analog inputs as project requirements changed. Rewiring the box was a pain, as it was not designed from a modular standpoint. No wires were labeled, and nothing was documented, so it was a pain.

As we ran out of analog channels set up in the box with panel mounts, we had to modify the box and begin to add other panel mounts, which was time-consuming.

We also had this large box with a fancy data acquisition and control device (LabJack T7), but it could only support analog channel readings.

We also had sensor noise issues which caused sensor readings to be terrible, and nothing was voltage protected, which then eventually led us to frying our 800$ data acquisition device.

Solution

When I became manager of Ground Support Engineering, I re-designed the box, from a modular standpoint, and also upgraded the box to support relay control, PWM control, encoder reading, up to 80 analog channel inputs, sensor shielding to reduce noise, and voltage protection for the data acquisition device.

Above are schematics of the Relay Board that interfaces with the LabJack to support relay switching.

While I would like to specify that I did not do the technical design of the PCB, I led the high-level PCB design for a Relay Board that connected directly to the LabJack. It included overvoltage protection on all LabJack inputs,  overcurrent protection, analog voltage feedback to monitor relay states, and flyback protection for solenoid switching. 

The new DACS Box included sensor inputs on the left and control outputs on the left. Each wire was labeled to show which panel mount and pin it led to. The wires were color-coded also, to show if it was ground, voltage, analog signal, shield, or control signal.

An extensive documentation sheet was created as well, to document the entire box and its current wiring setup.

Conclusion

The new DACS Box saved countless hours of troubleshooting sensors and facilitaiting fastly changing project requirements. 

There were countless times when propulsion wanted to add another sensor on the day of the test, or a sensor was not working day of test and we had to troubleshoot. The new DACS box made solving those problems easy.