John OpsahlInitial cost estimate for a single OpenDendrometer is $70. The 3D printed parts are the largest contributor to total cost. So if you have access to a 3D printer, you could build an OpenDendrometer for around $45.
I have planned to develop a custom PCB to make assembly very easy, but it's likely possible to make all the connections with jumper wires. Using jumper wires would shave an additional $8-10 off the total cost.
All costs for purchased items in the table below are based off of list price on Amazon.com. I would guess that sourcing all of the purchased components from Aliexpress could reduce total cost by 20-30%. The downside is that lead time for items purchased from Aliexpress is usually somewhere between 3 and 8 weeks.
| Qty | Description | Cost Per Unit | Total Cost |
| 1 | digital tire tread depth gauge | $8.99 | $8.99 |
| 1 | ESP32 microcontroller | $6.66 | $6.66 |
| 1 | lithium battery, 1800mAh | $7.18 | $7.18 |
| 1 | micro SD card module | $1.00 | $1.00 |
| 1 | micro SD card | $4.99 | $4.99 |
| 1 | DS3231 RTC module | $3.40 | $3.40 |
| 1 | logic level shifter, 4 channel | $1.60 | $1.60 |
| 2 | 2N7000 mosfet | $0.08 | $0.16 |
| 1 | custom PCB | $10.00 | $10.00 |
| 1 | custom 3D printed parts | $25.00 | $25.00 |
| 1 | screw, 200mm | $1.00 | $1.00 |
| Total | $69.98 |
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I think you're greatly overestimating the current cost of PCB fab. Using one of the overseas companies, a board small enough to fit inside your enclosure is unlikely to cost more than $2 or so even in quantities as low as 5.
Though even if it really did cost as much as you've estimated here, I'd say it would be more than worth it. There's just no comparing the reliability of a professionally made PCB versus using jumpers and a breadboard. Especially for an outdoor application like this.
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Good point Tom. I can still count the number PCBs I have designed on one hand. Usually, I have gone through OshPark in quantities of 3. So that is where the $10 per PCB estimate comes from.
Will definitely be looking for strategies to achieve total cost less than $50 once I am able to collect some actual data with the current OpenDendrometer architecture. Thanks for the tip.
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Understandable. OSH Park are great people and absolutely worth supporting, but they are FAR more expensive than the competition. Of course, one could argue that you get what you pay for...
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