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Board Received, Assembled, and Tested
10/19/2022 at 03:58 • 0 commentsAnd after all that assembly, I uploaded the Arduino sketch. The board works! It successfully logged several measurements from the digital gauge with timestamps to the SD card. I am very excited to get this installed on a tree and collect some real data.
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OpenDendrometer v0.1 Material Cost Estimate
10/16/2022 at 01:53 • 0 commentsThe current material cost estimate for a single OpenDendrometer v0.1 is $50 USD. See cost breakdown by component in the table below. The two highest cost items are the lithium battery and the enclosure at around $7.75 each. $50 falls right in the middle of the "shall" requirement of $60 and "should" requirement of $40 that were established at the beginning of this project. Overall, I am excited to have achieved the original design requirements and look forward to exploring strategies to further reduce material cost.
For more a more detailed breakdown on these costs and information on where these components can be sourced from, see the "eBOM" spreadsheet of the "OpenDendrometer_EN" workbook in the files section of this project.
Qty Description Cost Per Unit Total Cost 1 digital tire tread depth gauge $4.27 $4.27 1 Arduino Pro Mini, 3V/8MH $2.12 $2.12 1 lithium battery, 2000mAh $7.67 $7.67 1 micro SD card module $0.38 $0.38 1 micro SD card, 16GB HC $1.99 $1.99 1 RTC module, DS3231 $3.75 $3.75 1 coin cell battery, 2032 $0.61 $0.61 1 logic level shifter, 4 channel $0.30 $0.30 1 mosfet, 2N7000 $0.14 $0.14 1 Bluetooth BLE module, AT-09 $4.05 $4.05 1 OpenDendrometer PCB $4.00 $4.00 2 6 position header connector 2.54mm, through hole, right angle $0.66 $1.32 1 JST B2B-PH-K, 2mm spacing,1 row, 2 contacts $0.01 $0.01 1 OpenDendrometer laser cut parts, baltic birch plywood, 3.18mm $4.00 $4.00 1 electronics enclosure, 158x90x60 $7.84 $7.84 1 shaft collar, 1.6mm shaft $1.68 $1.68 1 aluminum angle, 25x25mm, 1.6mm thick, 130mm long $2.50 $2.50 4 nut, M5, stainless $0.06 $0.23 2 threaded rod, M5, stainless, 100mm $1.50 $3.00 Total $49.85 -
OpenDendrometer - Pencil on Paper
10/14/2022 at 04:17 • 0 commentsBefore it became a piece of hardware and before it was built out in CAD, the OpenDendrometer was an just idea in my head and a few sketches on paper. Pencil on paper is where it has taken the most forms and seen the most failures. These pages of my notebook follow the progression of the OpenDendrometer from concept to detailed design.
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Laser Cut Parts
10/12/2022 at 04:08 • 0 commentsI was able to stop by the local makerspace over lunch to laser cut the new OpenDendrometer parts today. All the new parts are looking great so far!
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PCB Out For Fabrication
10/11/2022 at 03:12 • 0 commentsI finalized the first version of the OpenDendrometer custom PCB design this evening and submitted it to a board house for fabrication. The boards should arrive in up to six days.
I looked at quotes from two board houses. Best option from Oshpark was qty 3 boards in 4-5 business days for $165. Best option from JLCPCB was qty 5 boards in 6 or less business days for $30. I like Oshpark for board quality, but I don't want to spend twice as much as their standard option to expedite that level of quality. Choosing JLCPCB this time.
I have lots of exciting ideas on how to decrease the power consumption of the OpenDendrometer board, but I am holding back on including those now in the first board version for the sake of reliability. I have breadboard tested this configuration many times and have even run field tests with it. I have high confidence that it will work. In combination with a entirely new enclosure design and inclusion of the Bluetooth module in this sprint for the Hackaday Prize 2020 finals, I have already introduced enough opportunities for additional challenges. Staying safe on the board design for now so I have time to address those.
Even though I ran through all the checks I could think of, I was still nervous to submit this board for fabrication this evening. I usually like to a few days to mull it over while I work on software. Schedule doesn't allow that this time so it really seemed like a leap of faith. Crossing my fingers.
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Preliminary PCB Trace Routing
10/09/2022 at 17:13 • 0 commentsFirst pass of trace routing for the OpenDendrometer custom PCB is complete. Not a lot of room in the schedule for rework so it is important that this design be near perfect. Fortunately, I am working with low frequency circuits on this PCB design so "near perfect" is more an exercise of "connect the dots" than partitioning component types, establishing keep out zones, and managing return paths. Since component placement on this board is highly dependent on mechanical design there is not much opportunity these strategies anyways.
I often notice that some are scared away from hobby level PCB design because of the perceived complexity of component placement and trace routing. Maybe it is a combination of luck and using prefabbed hobby electronic modules, but I have fat fingered all my hobby PCB designs without issue. Just connect the correct dots, do not overlap traces, and ensure return paths on the ground plane exist. Crossing my fingers that my luck doesn't run out with this scrappy, hacked-together approach on this PCB design.
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Preliminary Component Layout
10/07/2022 at 23:08 • 0 commentsCompleted preliminary component layout in MCAD (mechanical CAD) and ECAD (electrical CAD) today. The approach I usually take is to guess at component layout and board dimensions first in MCAD. Then import these dimensions as DXFs into ECAD. Component placement in ECAD becomes aligning roughly to the layout initially established in MCAD. It is very easy to make a change in MCAD and reupload to ECAD if needed. I have found that this approach plays to the strengths of each type of engineering CAD software.
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New Tree and Fruit Enclosure Mounting Solutions
10/07/2022 at 18:35 • 0 commentsTree Mounting Solution
Threaded rods on left side of the image are screwed into the tree.
Fruit Mounting Solution
Cable ties are used to secure the plate at the center of the threaded rod to the nearest tree branch. The "star" feature on left side of image ensures that the fruit remains centered on the dendrometer probe.
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Progress on Prototype Enclosure and PCB
10/04/2022 at 03:21 • 0 commentsThe new enclosure design is looking great. The plan is to mount the tire depth gauge to the PCB using laser cut parts and fasteners. Then fasten the PCB to the IP rated electronics enclosure. This design only requires two custom modifications -> trim down the sides of the tire depth gauge and drill a hole in the enclosure to allow tire depth gauge tip to pass through. Still many opportunities for improvement on this enclosure design. Many of those will have to wait for now as am rushing to get this initial prototype design put together in the next two weeks.
The schematic came together quickly because, just like the breadboard development unit, this prototype will be using several hobby electronics modules.
I originally thought I was going to use ESP32 for this project for it's wireless capabilities, but incidentally seems like Arduino Pro Mini with a Bluetooth Low Energy module is a better choice to minimize power consumption. I still have not had a chance to breadboard test with the BLE module yet. That is next on the list.
I plan to get a PCB hole pattern mockup laser cut either tomorrow or the next day for some quick fit checks. I will do this before I move forward with component placement on the board in KiCad.
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Mad Dash to the Hackaday Prize 2022 Finals
10/03/2022 at 02:16 • 0 commentsOpenDendrometer has advanced to the Hackaday Prize 2022 finals! The finals close out on the morning of October 23rd -> so just 20 days to finish the first OpenDendrometer prototype and add content to the project page!
I have six big project improvements planned for the finals:
- Custom PCB. A breadboard development unit no longer meets the requirements for extensive field testing. A custom PCB is required and I can't wait to get started.
- New enclosure design. The field tests proved that the previous 3D printed PLA enclosure design does not withstand the elements (it softened at just 30°C). The enclosure will be a standard plastic IP rated, electronics enclosure with a few modifications.
- Wireless data transfer. Manual data transfer over USB or with an SD card is not viable for locations that are difficult to access and for collecting data from a large number of units. Wireless data transfer has to be in place for the OpenDendrometer solution to scale easily.
- Two days of field data. Additional field testing is the only way to prove out all the new features.
- Three minute video. An video that introduces the OpenDendrometer, explains the user experience, and describes the architecture.
- Build instructions. A complete set of build instructions and design files so others can build OpenDendrometer units.