SeaPerch Tips

By Allen Wallace, Larson School UUR instructor

1. To be politically correct, in the classroom, I use lead-free solder from Lowes or Home Depot,. The “3 oz Lead-Free Electronics Solder” costs only $13.48 and works well.  FYI, in my home workbench, I use 60/40 tin/lead solder.

2. I always test the PCB and motors first  using a low-current (short circuit proof) power supply. This prevents unnecessary fuse blowing. This power supply can be a wall-wart (wall transformer) with a voltage between 5 and 15 volts.. A typical motor only consumes 30 milliamps at 5 volts, so almost any wall-wart will work. A 9-volt battery will also work.

3. Always have the student dry their hands when operating the SeaPerch controller. From experience, drops of water fall into the switch barrels and short out the switches. 

4. Waterproofing the motors:   If wax gets inside the motor, and it has excessive internal friction, all is not lost. I have successfully used a hot air gun to melt the wax from inside the motor after it was removed from the film can and the black tape was removed.

5. I use many, many plastic zip ties. Get them cheap at Harbor freight.

6. A BIG problem is that the propellers fall off the motor shafts. We see floating props in the swimming pool all the time.

1. Roughing the motor shaft makes a HUGE improvement!

2. Use good glue. I use epoxy.

3. Test your glue job by pulling on the prop. 

7. Recycling! To keep BYU’s cost down I try to reuse:

1. The motors, however I have a high failure rate due to water contamination, so try to be careful!

2. Cat-5 cable, speaker wire, fuses  and fuse holder.

3. PVC elbows and tees.

8. I do not recycle pipe, switches, PCB and the plastic enclosure.

9. For emergencies at the pool, I use telephone “B-splice” connectors, which allows for easy motor replacement in under a minute. Yes, I carry a few spare recycled motors for my teams.

10. A common problem is misaligned switches and their drilled holes. .After the switches are soldered,it is virtually impossible to fix this. To prevent this, I follow these steps

1. Precisely drill the ¼ inch holes in the lid of the black plastic enclosure using a template. I use a 3D printed template, which allows my 5th-grade students to get it exactly correct.

2. If you do not have a template, create a paper template with three tiny holes exactly 28 mm apart.

3. Position the template centered on the lid of the enclosure and tape it down so that it will not move in the next step.

4. Use a nail to center punch the paper template holes, which makes a small divot in the plastic of the lid.

5. Use a ¼ drill bit to drill the plastic. The tip of the drill bit is positioned in the small plastic divot which prevents the drill from wandering.

6. Next, install the three switches in the lid and use finger-tight force when tightening the nuts.

7. Then place the PCB onto the switches. You may need to rotate the switches to get them to align correctly.

8. If your holes are misdrilled, then the switches will not fit in the PCB.  You will need to elongate one or more drill holes. I do this using a round file or using a drill bit and applying sideways force.

9. When the switches are in the lid and the PCB on the switches, then you can solder with confidence that everything is lined up correctly.