Sensor Deployment Arm

An armature for deploying sensor probes into the water was added to AMOS this week. It was basically the simplest design that I could think of; a lever arm connected to a servo motor that swings back and forth with the sensor probe cables attached to it. When swung toward the water, it pulls the probes into the water to deploy them. When swung back in the opposite direction, it pulls the probes back onto the stern deck.The probes are not overly heavy so I didn't bother with any strain relief for the electrical cables. My home-made turbidity probe is possibly a bit too buoyant, so I may need to add a bit of mass to it.

Here is a video of the armature in action in our pool today:

The first time I tried it out in the pool a couple of days ago, I noticed that the turbidity probe output changed drastically by almost 50% after a few minutes of being deployed in the water, and that the probe had settled lower down into the water. Unfortunately the enclosure had flooded with water. After taking it out, emptying out the water, and studying it for a bit, the most obvious source of water intrusion were a pair of fastenings on the underside of the shell. Here is a photo of one of the fastenings:

I built the turbidity shell last year, and I think I must have been planning on filling the holes with some molten 3D printer filament, but never got around to it. So last night I held the probe upside-down under my 3D printer nozzle, turned on the heat, and then manually fed the printer filament through the nozzle so that it dripped down into the hole, filling it up completely. I then smoothed it out later with a heat gun and my finger (hot ouch!).

The blue printer filament sort of looks like a wad of gum. I'm hoping it will be more water-tight than that though. Tomorrow I'll let it sit in the pool for a while to see what happens. If it doesn't work, I'll try 3D printing a new shell without through holes for the fastenings.