7.0 building the controller jar - gallaudet...

ROVs In a Bucket – Building an Underwater Robot

7.0 Building the Controller Jar 7.1 Introduction: This is the most technical of the tasks needed to build the ROV. When you’re done here, you’ll be able to power up each of the three thrusters separately. Each will be able to go forward, or back, independently, depending on which labeled switch is engaged. The figure below is what your controller jar will look like.

Figure 7.1: The completed controller "jar".

To build the controller jar, you’ll need a 3/8” drill bit, a pair of pliers, a silvesharpie, and three of the switches you wired in Chapter 6 - Switches.

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Figure 7.2: What you need to get from here to there.

Building the Controller Jar Assembly [email protected]

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Take an empty controller jar and separate the top. Put the jar aside for the moment.

Figure 7.3: The lid of a jar Mark the top with a triangular pattern. Separate the triangle corners so that its easy to operate the switch toggles. Don’t put the holes to close the lid walls, otherwise the switch body might not allow the lid to tighten onto the jar.

Figure 7.4: Marked for holes where the switches will go

Drill the marked holes with a 3/8” twist drill. Clean the holes of any plastic fragments.

Figure 7.5: Lid with drilled holes for switches.


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Install three switches into the drilled holes. When installing the back side of the switch should lie flush against the lid plastic. Where the toggle comes out of the lid install the flanged washer directly over the plastic and then thread the nut onto the switch toggle threads.Don’t tighten the nut yet. Note the silveline markings on the top. We’ll cover addition of these in the next couple of paragraphs.

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Figure 7.6: Lid with switches installed and marked in the direction they can be pushed. Before the switches are tightened against the lid, make sure that all of the wires are on the same side. Turn the lid over and inspect the switches. Each of your switches has four bare wires. The black and red wires in the switches center posts bring the power to the switches. The red and green wires that come from the switches corners allow the power to be applied to the thrusters. Each switch will be wired to one thruster assembly. When the switch is activated in one direction, the thruster propellers will turn one way. When the switch is activated in the opposite direction the electrical polarity will be reversed and the propellers will reverse their direction (hopefully).


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Figure 7.7: Backside of lid with all switch wires in the same position. In the figure above, the black wires are located on the right side of the switches in the photo. The middle, red (power) wires are on the left side of the image. All of the green wires cross from upper right to the lower left. All red switch wires cross from the upper left to the lower right. When all of the switch wire colors and connections are in the same position the thrusters will operate in the same direction when any of the switches are engaged in the same position. For example, when all three switches are pushed “up” at the same time all of the thruster propellers will spin in the same direction. If all switches are engaged simultaneously in the “down” position, all three thruster propellers will spin in the same identical direction, opposite of the “up” position.

All the switches should engage in the same direction. You don’t want one switch going from left to right and another top to bottom. They should all engage when pushed “up” or “down” in the same direction. Use the silver “Sharpie” and put lines on the lid in the direction that the switch should be pushed. Invariably, some (usually kids) will insist on pushing the switch in ways that it cannot possibly work. These switches will bend and break if forced where they don’t want to go. The only protection against this is by watching the operation with operators that might get excited under pressure and start forcing the switches into awkward positions. Put the lid aside for now.

Figure 7.8: Top of controller with switches installed and marked.


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Take the controller jar and drill a 13/16” hole in its base. Hard plastic jars will crack if the drill is advanced too quickly. If the jar is made of a softer plastic it is less likely to crack by drilling.

Figure 7.9: Threading the power wire through the controller jar base.

Figure 7.10: 13/16" wood bit for drilling the hole in the jar base. I’ve been successful drilling this hole in plastic jar bottoms using a 13/16” wood bit (figure 10). I use a drill press with a base that has a 1” hole in the drill platform. This hole allows the drill to pass through the jar bottom when the hole is complete. Without this, the drill will be stopped by the base that the jar is being held on while the hole is being drilled. I hold the jar against the platform and advance the wood bit SLOWLY making certain that the drill is straight – up/down. After the drill point penetrates the jar bottom, it will advance more quickly. Note when the wood bit “paddles” engage the jar bottom. By putting just a little pressure on the drill it will “shave” the plastic off of the bottom. Be patient, and the drill will soon pass through the controller jar bottom. Now install a ½” PVC male adapter (Figure 7.11, below, left). Put the threaded end through the bottom of the controller jar so the threads are outside of the jar. Thread the locknut (Figure 7.12, below, right) onto the threads and tighten it until it is against the jar bottom. If you over-tighten this nut the jar will crack, so just make it snug.

----- Figure 7.11 Figure 7.12 - ---


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Locate the 10’ length of speaker wire. Separate each end so that about 4” of the double strand wire is separated into singles. Now strip each end so that about an 1 ½” of bare wire is showing on one end and 1” on the other..

Attach electrical connectors to the end of the 1 ½” bare wire ends (Figure 7.13). Later, these will be hooked to the power supply when the thrusters are “powered up” with the battery pack

Figure 7.13: Electrical connectors to the battery pack

Thread the other end of the power cable through the male adapter that was installed at the bottom of the controller jar. Pull it through so you’ve got plenty of “end” to work with (Figure 7.14).

Figure 7.14: Pass the power cable through the bottom of the controller jar.


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Now its time to attach the power cable to the power wires of the switches. We’ll attach the copper power wire to the black power wires on the switches. The silver power wire will be attached to the red power wires on the switches. Gather the three black power wires from the middle posts of the switches. Cross them and twist them to connect them. Now, bring the copper end of the power wire to the connected ends of the black wires and twist them together so that all four of these wires are connected (Figure 7.15). There are several ways to secure the four wires. One is to

use a wire nut (Figure 7.16). With all four wires twisted together the cylinder of wires is shoved into a wire nut. The wire nut is twisted in a clockwise direction until it tightens around the wire. A second way to secure these four wires is to twist them together, and then put a couple of plastic tie wraps around the bundled wires. The plastic tie wrap method of securing the wires does leave bare wires exposed. This should nopose a problem

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Figure 7.15: The red and green power wires are twisted together.

they’re secured inside the controller jar. A precautionary measure to help prevent future problems with the bare wires would be to wrap it with some electrical tape. Figure 7.16: The three black and red power wires from the switches are attached to one of the two power wi


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The wire that brings electricity to the switches is now attached. Next, we’ll start wiring the thruster assemblies to the controller system. This will be done one at a time. Every time a switch is connected to the power the system it is important that it be tested. Thread the un-connected end of the tether through the bottom of the controller jar where you’ve already put the power cable (3 pairs of the speaker wire (see Chapter 5 - Tether Build). At this time cut three 1” pieces of green and three 1” pieces 3/16” shrink tube. Slide the red tubes over the silver wires and the green over the copper (Figure 7.17).

Figure 7.17: Each of the three wire pairs, one green, one red will connect one thruster to one switch. Each of the three switches you’ve built has a red and a green wire connecting the opposite corners of the switches you’ve built. Now, we’ll hook these up so that the thrusters will receive power when they are engaged.


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Figure 7.18: After connecting each wire the connection will be tested. Physically locate the red and green wire from one of the switches. It is not important which switch you choose. Now select a thruster wire. It’s not important which one you choose. Twist the silver wire onto the red wire. Bend the wire away from the red shrink tube. Slide the shrink tube to cover the bare wire. Now, twist the copper wire onto the green wire, bend it away from the green shrink tube, and slide the shrink tube over it. Use the heat gun to shrink the tube around the wire (Figure 7.18).

Prop the three thrusters up so that the propellers will not hit anything when they spin (Figure 19). Make certain that they are spaced so that the propellers will not hit the other thrusters. Figure 7.19: In this photograph, the thrusters placed too close together for testing. The blades will hit.

In Figure 19 the thrusters are propped upright, but not spaced far enough apart. The center thruster propeller will hit the left thruster when it is powered up. It is also


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important to make sure that the propellers and the prop adapters are secured to the thruster (see Chapter 3 – Propeller Attachment).

With the first switch “wired up” hook the power cable to the power source. Clamp one of the electrical terminals that you installed on the end of the power cable to one of the connections on the power source (Figure 7.20). It’s not important to connect red to red, or black to black at this time.

Figure 7.20: The connectors to be attached to the power source. Switch the power on the “Jump Start” (Figure 7.21) to the “ON” position. Note that the power coming from the jump start is completely harmless. With the battery pack on, if you held both the connectors at the same time, you would not feel any electricity passing through. There would be no shock.

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ounterclockwise. .

igure 7.21: The power source.

in. Note the direction that the propeller is rotating, e. clockwise, or counterclockwise.

Be certain that the thrusters are secure for testing. Push any of the three controller switches to the “ON” positions. Pay particulaclose attention to the direction that you engagethe thruster. Note, for example, that when you push the switch to the “up” position, the propeller rotates either clockwise or c

F One of the three thrusters should spi.


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wo of the three thrusters are connected to the switches. The last is ready for onnection.

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reen with the silver strand and the thruster will spin in the other direction.

Figure 7.22: Tc Next, we’ll connect the second switch to the power wires (Figure 7.22). We’ll pause aftethe bare wires are twist connected to the power cable and the shrink tube is slid downover the pair. With the second switch set connected, push the switch and make sure that one of the thrusters props starts to spin. Note whether the prop spins in the same direction as the first one that you hooked up. If it does, that’s great. If its opposite, thits not a big deal. Just hook the red wire up with the copper speaker strand g


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Figure 7.23: All of the tether wires are connected to the controller lid. In Figure 7.23 all of the wires are connected. Each of the three pairs of speaker wire leading to the thrusters has been connected to one of the dpdt (double pole – double throw) switches on the controller. At this time, when the power supply is switched on, all of the switches should be controlling one of the three thrusters. Knowing that you were careful in testing the direction of the spinning thrusters after connecting each switch, If all three switches are pushed in the same direction (“up”, for example) all of the propellers will spin in the same direction. If they don’t spin in the same direction there are a couple of remedies that can be applied to correct this. If there is a thruster turning the wrong way - When you look at the backside of all three switches, are the same color wires all on the same switch post? If they are not, you can cut the plastic tie wrap holding the connectors to the switch and correct them. This should solve the spin problem (See Chapter 6 – Switches).


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Figure 7.24: The wiring is complete and a couple of tie wraps are applied to keep the wires from being pulled out of the switch posts during operation. With the controller wiring complete, we’re ready to complete the jar assembly. Gently hold together the four wires coming in from the bottom of the jar. Take two 4” plastic cable ties and secure the wires, as seen above (Figure 7.24). If the tether is pulled the strain will be put on the bottom of the controller jar and the wires should not be disconnected from the switches.


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Figure 7.25: The completed controller assembly Now, gently, slide the controller jar up to the lid and tighten the lid just like you would put the top on a screw on jar. Test the controller with the power on again, to make sure that it is fully operational. Now, apply two more plastic cable ties to the bottom of the jar where the tether enters it (Figure 7.25). The Controller is now connected to the thrusters. At this point we’re ready to build the underwater ROV and launch it into fresh water (preferably a pool).


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7.0 building the controller jar - gallaudet...

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