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Message ID: 669     Entry time: Tue Jul 16 00:15:08 2013
Author: Giorgos 
Type: DailyProgress 
Category: SUS 
Subject: Digital Voltage Meters, Labeling and Rest 

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.

DigMeter.eps

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.

Labeling

We labeled all the wires in our DC Motors Box:

  • the wires connecting the 6 PCB boards to the fit-through board; either Motor_orientation (such as TS-top south), or Gauge_orientation.
  • the wires connecting the push-buttons to the PCB boards, receiving strain gauge output and sending the signal

Rest

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

Tomorrow, we need to do the following:

  • make the labels for the HE sensors and Coils' boxes
  • finish fit-through boards for HE & coils' boxes
  • cut 4 panels for coils, so that the PCB boards can fit inside the box
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