domingo, 30 de março de 2014

March 24th

On this week I’ve been doing a several things. As in every project, it’s essential to have the documentation of all the work! This week I started to draw all the circuits of my hardware and to project the PCB Board in Eagle, as I said that I would be doing before.

The board is meant to be able to gather all the data from all the sensors, which are a force load cell, a force sensor resistor (FSR) and an infrared distance sensor, amplify the signal and convert it from tension to current. This last requirement is very important because the sensors will be far away from the Arduino. If the signal goes from the sensors to the Arduino in tension the signal may vary due to the resistive wire losses and as well, in current the signal has a greater electrical noise immunity.

The first board that I made, as you can see on the figure, doesn’t have yet this V/I converter so I’ll be making a few changes on the next week to add that.

Figure 1 - Acquisiton board made in Eagle Software.

Also the board has only three slots for one of the kind of sensors that I mentioned, however I’ll be using two of each kind so I’ll have to add more connectors too.
As for the connectors, I am using molex connectors but they are not the best considering their size and utility, so I’ll be switching those for RJ45 connectors for the supply and the signals, that able to have 8 wires in just one cable, and JST-H connectors for the sensors, that are much smaller than molex.

At the same time I’ve been creating a new package in ROS with a script in C++ that reads the data from the hardware and displays it as a kind of progress bars on ROS-RViz. 

Figure 2 - Displaying data on RViz, green - load cell, blue - FSR and red - IR sensor.


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