Receiver Box / Start Logger
Our customer needed an enclosure for a Raspberry Pi 3B+ with a Witty Pi 3 hat and an Adafruit PiTFT stacked on top. Furthermore, he needed two USB ports and a Micro USB power port to be accessible from the outside, as well as the PiTFT touchscreen and 4 hardware buttons. In addition to the Pi, the two hats, and the two other components to go inside there needed to be two holes for banana plug connectors that came with specifications, which will connect to a small custom circuit board (with Gerber files), as well as an Arducam CSI-HDMI extender where the female HDMI port is accessible from the outside and the CSI cable is connected to the RPi camera connector.
Quantity needs is for 1 prototype, but once the prototype is approved, anticipated volume of 100 in first 6 months
The customer had some rough designs for all of these. The original design consisted of 2 shells screwed together. This design could be a good fit for our process, but not really cost effective and would require a some unnecessary workmanship. here is below the first design idea from our customer:
Since the enclosure will be used in a very wet environment, we first thought to design the enclosure watertight but our customer has other requirements: The receiver box does not need to be watertight, but since it will be sitting by a swimming pool, it should be at least splashproof and rainproof, if possible. I’d also like to have the ability to mount this to a pole, so a 1/4″ 20 threaded hole would be good so I can mount it if needed. Instead of a Witty Pi 3 board, I decided to go with an RPi UPS hat (https://www.pishop.us/product/raspberry-pi-ups-hat/) instead, with the Adafruit PiTFT (https://www.adafruit.com/product/2423) stacked on top. The battery intended to use is this one: https://www.batteryspace.com/li-ion-18650-battery-3-6v-13-4ah-48-24wh-7a-rate-4s-s-ncr18650b.aspx. The dimensions are 2.9″ (74mm) x 2.66″ (68mm) x 0.8″ (21mm). UC-392(B0091) v2 is the CSI-HDMI board, and I believe the PCB1 board is the signal conditioner. The two screws from the banana plug connectors go through the holes on that board.
An electrical engineer had also taken a look at creating a hat for the RPi that combines the LCD, the UPS hat, the signal conditioner as well as the CSI-HDMI board. The goal is to be able to revise the enclosure to simplify it without having to pay another setup fee.
As for color and logo – I would like the plastic to be white, and the logo either printed on it in blue or engraved.
2 circuits boards were ordered and sent our way:
- From Amazon – Raspberry Pi 3B+ and 2 pieces of Arducam CSI-HDMI adapter (they come in pairs, but you only need one per box)
- From Adafruit – the 2.8″ TFT with the 4 buttons
Later came a signal conditioner board (PCB1) separately.
Ongoing design processes and challenges: Receiver Box
This receiver box is intended to be either a Start Logger (the box that records the exact time of each start – getting the signal from the banana plugs) or a video recorder box (getting the video through the HDMI port on the CSI-HDMI adapter board). The enclosure will be used around pool areas, and subject to water splash. The device is not supposed to be going underwater.
- The first challenge was to actually make contact buttons for the touchscreen. Understanding that water could get in there, but hoping that it won’t be that big of a problem. The device can be put into a box that will be close to the pool’s edge in a watertight box while the meet is going on, but no need for the boxes that are attached to poles outside to be able to withstand rain. The best option to make these buttons was to mill on a thick piece of plastic. This is not an ideal solution when it comes to milling, but will meet perfectly our customer needs. His quantity was not big enough to amortize the price of a mold, and it did make sense for him to pay a little bit extra in order to avoid making a mold.
- Another design question was to make sure the pool device could be mounted on a pole. We added a ¼-20 threaded insert for the pole mounting along with a milled “standoff” to accommodate clearance with the plastic enclosure
- The battery type also needed to be modified. Our customer was wondering if the battery I selected could be made into a different shape. Essentially, the battery pack is composed of 4 cylindrical 18650 cells bound together with a vinyl wrap. Instead of laying them out next to each other like they are now, we were going to see if they can stack them 2×2, so 2 cells next to each other with 2 cells on top – leaving a square cross-section. If they can do this, then you can put the battery on the GPIO pin side (the bottom when it is sitting with the screen facing forward) of the case. Unfortunately, It turns out that the battery supplier cannot change the configuration of the battery without voiding their UN38.3 certification, so the battery will stay the same shape that it is.
A few more changes were expressed by our customer:
- A hole so the user can press the button on the UPS board (should be plugged up with a cover normally), as I discussed in my last message
The customer took the screw out and they used a L-Shape Hex tool and hit the top of the button.
- I do need a slide toggle switch in the battery compartment. The openings I need for this switch are contained in this STEP file attached.
- Would it be possible to keep the current design but just add in an access door for the battery compartment? Something that takes a little effort to open – like a latched hinged door or a “push and slide” door, etc.?
We were able to add a removable L-shaped door that slides and screws in from the bottom and back of the enclosure. The L-shaped door would be secured from the bottom with one small screw. That was the simplest and most effective way to do without drastically changing the design.
Instead of a battery compartment, we added a removable internal plate, in order to install an access circuit board and display.
All in all, another well designed and well managed project by the Toolless team. Up for the next challenge.
Here are the Final Pictures of the receiver box enclosure:
Up for the next Challenge
TOOLLESS ALWAYS ONE STEP AHEAD