Choosing a logger design
Left: Prototype F. Right: BODAQS A8.
There are currently two BODAQS logger designs. Each has advantages and disadvantages, and your choice will depend on what you want to do and what is most important to you.
Available logger designs
Section titled “Available logger designs”| Design | Advantages | Disadvantages | Build this if… |
|---|---|---|---|
| BODAQS A8 | More input channels, more features, easier to build, more mechanically and electrically robust | More expensive if you get the PCB fabricated yourself, may be overkill | You plan on running lots of sensors, or you always go top-shelf |
| Prototype F | Can be cheaper | Fewer channels, can be fiddly to build | A few channels is enough, cost minimization is key |
Why two designs? What’s the difference?
Section titled “Why two designs? What’s the difference?”The BODAQS logger design has been through a lot of iterations. The early designs used an off-the-shelf ESP32 development board as the ‘brains’ of the logger, and a custom PCB that mostly just made it easier to wire connectors. As I learned more about electronics design and gained experience with data acquisition in the real world, some limitations became apparent.
Birth of the BODAQS A8
Section titled “Birth of the BODAQS A8”The BODAQS A8 is my first ground-up design where all the components are integrated directly onto a single PCB:
- It has a better power supply design for driving analog sensors.
- It has two precision analog-to-digital converters (ADCs) supporting up to 8 analog inputs.
- It has a real-time clock with its own backup power (this is a big deal if you want to combine GPS data from a Garmin device with your log data).
- It has the navigation buttons mounted directly on the PCB.
…and most importantly, it has connectors soldered directly into the PCB. By my estimate, that one thing reduces the build time by about 60% compared to the Prototype F. It probably improves reliability too.
Prototype F: Not dead yet
Section titled “Prototype F: Not dead yet”Why would you still build the earlier ‘Prototype F’ design then? Mostly it’s a question of cost.
Minimum order quantity for custom PCBs (from JLCPCB) is 5, which is more data loggers than most people need. With a simple design like the Prototype F, 5 is still cheap enough for most people not to really worry about. A lot of the hardware is on the plug-in development board, and you can buy those one at a time.
The BODAQS A8, on the other hand, has everything baked in. That means you’re paying the complete hardware cost for 5 of them when you order from JLCPCB. That’s more than most people are going to want to swallow, unless they really need 5 data loggers.
Partly for this reason, I’m selling single A8 boards and parts kits myself. This ought to be a reasonably competitive option for people who want the newest (and best) design.
But I suspect some people may like the older approach better. As soon as I have the time, I’m planning to bring some ease-of-build improvements from the A8 to the older design (to be dubbed, creatively, the ‘A4’). But don’t hold your breath - it’s a little way down my to-do list.
Left: Prototype F. Right: BODAQS A8.
Is there an upgrade path from the Prototype F to the A8?
Section titled “Is there an upgrade path from the Prototype F to the A8?”No. The designs are different in almost every way.
When the A4 arrives (I do intend to do this, but no promises on the date) it will be possible to upgrade from the Prototype F re-using dev board, keypad, battery and possibly case (but not connectors).