Background: I’m building up a mail order business that has to pick orders every day from stock and ship them. To make this easier and faster i was thinking to build a “pick by light” system where every space in the shelf has 7-segment displays, a bright RGB LED and a button. When an order gets loaded, the system will display number count on each numeric display and flash the LED in green. When i pick the products into a box i press the button and the LED stops blinking, and the number count will show zero or “—”. it can use a different color for the LED to fill up stock to the right position . If i can manage to make this work i want to open source it and allow others to use the technology.
This is basically a normal pick to light system as you can buy it in the logistics. But existing solutions are all proprietary technology.
This system will consists of those elements:
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PCBs in a case with one or two 7-segment displays, and RGB LED and a button, mounted on each shelf space. (“Node”)
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A network connected micro controller that supplies a REST API to control all nodes in it’s section via some sort of bus. Probably a RasPi or NodeMCU or Arduino Ethernet etc. (“Section Controller”)
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A web server that loads an order from DB or API and sends messages to the Section Controller via their API (“Order Server”)
Section Controller and Order Server are pretty simple in terms of technology choice, but what i’m uncertain of is what would be the best way to let the Section Controller talk to the Nodes.
Right now i only need about 50 nodes but i would like to choose a design that makes it cheap to extend.
Coming to my question:
What’s a good choice for a bus system where each node has a display and an LED and can send push button events back and that keeps hardware costs low per node? Ideally i would connect to one or two dozen nodes to each section controller. Something that is well enough designed for scaling up to higher number than i need at the moment.