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Because it literally costs money to separate PCB material into separate boards, so there is a minimum cost associated with adding an additional bare board to a

Because it literally costs money to separate PCB material into separate boards, so there is a minimum cost associated with adding an additional bare board to a design. Which is more than you think. Connectors also cost money; often more than you'd think. And they add additional points of failure. Modularity also creates a compatibility matrix you have to track if you're a responsible OEM. I.e. can I use [X,Y,Z] sensor with [Q,R,S] base board and [A,B,C] MCU module and firmware [1,2,3]? In a model that may have shipped with motors [T,U,V]? That's 3^5 combinations right there. Compare that to, say, a single-digit or small two-digit number of actual combinations a manufacturer might ship as revisions over the life cycle of a design. You never have to worry about whether the Q base board will work with the C module in an integrated design. That $2 blue-pill STM board starts looking expensive really quick compared to the cost of the microcontroller (and maybe the crystals if you really need them) at even modest volumes. It just doesn't cost that much to add a chip or other subcircuit to a PCB design for a real product.

jacknews 5y ago
No doubt that is true, although I can imagine that if modules were made in their millions, and soldered (but still replaceable with rework), the cost disparioty would be less, especially with a saving on design/layout cost and the rework and revisions usually involved there. But the true cost, to the environment, savings due to repairing more modular machines, vs scrapping and manufacturing, shipping, installing, etc whole new machines every few years, could be way less.
- buescher 5y ago
  What's the advantage of soldering a module in as opposed to soldering a microcontroller? What is the advantage of laying out a new module as opposed to laying out a new integrated board? Why do you think the level of modularity already in an appliance like a washing machine is insufficient? It's essentially never the microcontroller that fails in something like this, anyway, so you would never repair something by swapping out something like a blue pill dev board. Maybe you would swap in a microcontroller with a different pinout in production that way, to solve a shortage issue, but the development time and costs would be almost identical to just spinning the board. I really don't understand what problem you're trying to solve. Modularity costs, in a number of ways, and one of them is the material involved. That material will ship in every unit whether it is ever needed or not. When your more modular devices are beyond repair or obsolete or just unwanted all of that material will wind up in the landfill.
  - jacknews 5y ago
    Unsoldering a module would be much simpler, if the connection were designed for rework, and modules would be more commoditized. A simple example is my washing machine that recently died. A mosfet blew on the motor inverter/controller, and obviously took out some other components too. It's silicone-encased, making it infeasible to diagnose and fix compoonent by component. The entire electronics, including psu, mcu, display, buttons, and motor controller are a single unit, and has to be replaced. Since it's specific to the model, it is rare and expensive, and not economical to replace, so the entire machine is now junk, or at best spare parts. In my fantasy ideal, the motor controller would be a separate board, and fairly standardized to the motor size/design, just like stepper driver boards. The display/ui would be a separate board, since that is a common point of failure. The psu should certainly be a standard board. And the the main control board running the valves etc would again be it's own board. Interfaces and protocols between boards should be standard or at least documented. Yes, multiple, simpler mcu's. And slightly more material, etc, as you say, though for a washing machine, the added weight of a few electronics hardly matters. But much less custom design, inventory, much more repairable, reusable, upgradeable, hackable, etc. The washing-machine of Theseus, as it were. Another example is a toaster oven that recently broke. One of the elements shorted or burned out, it is one of a handful of standard sizes/resistances etc, rather than some custom proprietary design. Nice and modular, just as I want. BUT, the elements are riveted to the rest of the oven, rather than screwed, making a replacement significantly harder, to the point I haven't yet bothered (eg I don't have a metal drill-bit), and I bought a replacement oven (with screwed elements - the search was not trivial). A saving of a couple of cents (riveting vs screwing) for the manufacturer has actually cost me, and the world, much much more. IMHO the repairability of this stuff should be mandated, or at least documented right on the front alongside the energy-efficiency ratings and purchase price, etc.

jacknews 5y ago

No doubt that is true, although I can imagine that if modules were made in their millions, and soldered (but still replaceable with rework), the cost disparioty would be less, especially with a saving on design/layout cost and the rework and revisions usually involved there. But the true cost, to the environment, savings due to repairing more modular machines, vs scrapping and manufacturing, shipping, installing, etc whole new machines every few years, could be way less.

buescher 5y ago
What's the advantage of soldering a module in as opposed to soldering a microcontroller? What is the advantage of laying out a new module as opposed to laying out a new integrated board? Why do you think the level of modularity already in an appliance like a washing machine is insufficient? It's essentially never the microcontroller that fails in something like this, anyway, so you would never repair something by swapping out something like a blue pill dev board. Maybe you would swap in a microcontroller with a different pinout in production that way, to solve a shortage issue, but the development time and costs would be almost identical to just spinning the board. I really don't understand what problem you're trying to solve. Modularity costs, in a number of ways, and one of them is the material involved. That material will ship in every unit whether it is ever needed or not. When your more modular devices are beyond repair or obsolete or just unwanted all of that material will wind up in the landfill.
- jacknews 5y ago
  Unsoldering a module would be much simpler, if the connection were designed for rework, and modules would be more commoditized. A simple example is my washing machine that recently died. A mosfet blew on the motor inverter/controller, and obviously took out some other components too. It's silicone-encased, making it infeasible to diagnose and fix compoonent by component. The entire electronics, including psu, mcu, display, buttons, and motor controller are a single unit, and has to be replaced. Since it's specific to the model, it is rare and expensive, and not economical to replace, so the entire machine is now junk, or at best spare parts. In my fantasy ideal, the motor controller would be a separate board, and fairly standardized to the motor size/design, just like stepper driver boards. The display/ui would be a separate board, since that is a common point of failure. The psu should certainly be a standard board. And the the main control board running the valves etc would again be it's own board. Interfaces and protocols between boards should be standard or at least documented. Yes, multiple, simpler mcu's. And slightly more material, etc, as you say, though for a washing machine, the added weight of a few electronics hardly matters. But much less custom design, inventory, much more repairable, reusable, upgradeable, hackable, etc. The washing-machine of Theseus, as it were. Another example is a toaster oven that recently broke. One of the elements shorted or burned out, it is one of a handful of standard sizes/resistances etc, rather than some custom proprietary design. Nice and modular, just as I want. BUT, the elements are riveted to the rest of the oven, rather than screwed, making a replacement significantly harder, to the point I haven't yet bothered (eg I don't have a metal drill-bit), and I bought a replacement oven (with screwed elements - the search was not trivial). A saving of a couple of cents (riveting vs screwing) for the manufacturer has actually cost me, and the world, much much more. IMHO the repairability of this stuff should be mandated, or at least documented right on the front alongside the energy-efficiency ratings and purchase price, etc.