Week 14 – Electronics update

Back to the electronics once again!

We obtained 2 3-set H bridge circuit boards from Group 5 as they had an excess of them. As our design changed such that we won’t be using a rudder anymore to control the direction of the boat, the H bridges are required in order for the Arduino to be able to control the direction the motors turn in.

We had to modify 2 servos to make them continuous to be used as the spool motor. The normal DC motors could not be used as in their resting state, their shaft can rotate freely. However, a servo’s shaft requires much more force in order to turn it due to its very large gear ratio.

IMG_20160119_222751_HDRIMG_20160119_222321_HDRIMG_20160119_214158_HDR IMG_20160119_220505_HDRIMG_20160119_214151_HDRIMG_20160120_134043_HDR

The pictures above show the entire process. We had to saw off a metallic stopper on the gear and also cut out or melt the plastic stoppers on the servo cover. When we pieced it back together, we found that it was still limited, and had to take out the black rubber stopper sitting on the inside of the shaft gear. We also had to cut out the circuit board on the servo and connect the red and black wires directly to the motor.

With the H bridge in place, we can now control the 2 container spool motors and the 2 propeller motors for the vessel. The following is a demonstration of the electronics in its current state, capable of full-fledged logging of collection sample locations and with a robust set of controls.

Full feedback is incorporated, but the video does not show the motors actually moving yet as we are yet to make those connections. But logic-wise, this is the final version. One minor improvement we will make is to have more precise GPS locations recorded, perhaps to 5 decimal places instead of just to 2, for the latitude and longitude.

Ajay

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