Digital Voltage Meters
We need 5V to operate our digital voltage meters that indicate the offset from the strain gauge circuit in our DC motors configuration. One of the two power boards in the DC motors box had an unused 4-pin holder (+24V, GND, GND, -24V) and we will use that. To find the internal resistance of the digital voltage meters, we read the manual and the specifics of it: for 5V, the voltage meters source 400μA.
So, the internal resistance of the digital meters is R=V/I=12.5kΩ.We have two boards with 3 digital voltage meters each. They are all connected to the power supply and are in series with R1, whose value we want to determine so that we source enough current for all the resistors. We have six parallel voltage meters of 12.5kΩ each, so Reff=1/ (6/12.5kΩ)=2.08kΩ.
Each voltage meter needs 400mA, so we need in total I=2.4mA. That means that the resistance of the total system Rtot (=Reff+R1) needs to be 24V/2.4mA=10kΩ. Then, R1=7.92kΩ (we used 7.5kΩ). The meters worked fine.
We labeled all the wires in our DC Motors Box:
After completing the power wires for the DC Motors Box, we were almost finished; we only need very few components for the testing of the LEDs.
We also started fitting everything in our HE sensors box. We drilled holes/cut parts of our panels so that the PCB boards fit and then screwed the panels together.
Tomorrow, we need to do the following: