The most legendary aspect of LEGO bricks is the fact they've kept the dimensions compatible for decades. Maintaining such precision meant bricks made today can click into bricks I've had since I was little. Mechanically, the only deviation was their "studless" construction theme, which is a niche controversy I won't get into right now. New pieces are constantly being introduced with novel desirable properties, but they all click together in some way. However, the same could not be said of various LEGO forays into motorizing creations. Just in the various on-and-off times I've played with LEGO, I've managed to collect four incompatible motor control systems. Here are representatives from each generation, sorted left-to-right in order of age.

At the far left is the battery tray and switch for the oldest system. The battery tray is sized for three "C" sized batteries, which hasn't been in common household use for years. The switch toggles between two different ways to connect positive and negative power to wires, driving a motor either forward or back. It was possible to drive multiple motors simultaneously with multiple ports on the switch. Each plug can also accommodate another plug inserted on the side, but stacking connectors that way quickly becomes unwieldy.

To solve that problem, somebody had the idea that LEGO electrical connectors should conform to LEGO brick form factor. Such was the case for the gray cube which is a motor from the first-generation LEGO Mindstorm set. It was successful at letting us stack multiple motors in parallel, but there must have been some kind of problem motivating a change.

The gray cylinder represents the LEGO "Power Functions" line, which is very focused on studless construction except the connector, which is the same LEGO 2x2 size as Mindstorm RCX connector but with only two standard LEGO studs instead of four. The other half houses four electrical contacts.

Then I guess the person who felt LEGO electrical connectors should be LEGO bricks retired. Because that idea went out the door for Mindstorm NXT. Its style of electrical connector resembled landline telephone cables but was not compatible with them.

Today, fancy LEGO bricks use the "Powered Up" system, linked by yet another type of connector that remind me of SATA plugs for a computer's data storage drive but not identical.

That's at least five different ways LEGO has implemented electrical connections, and maybe there were more but I'm not enough of a LEGO historian to know. Why were these changes made? Some clue can be found in technical documentation written by people like Philippe "Philo" Hurbain who dissected and reverse-engineered their valuable LEGO components. Reading those pages, I understand the evolution as follows:

  1. The oldest system that used triple C cells only worried about powering a DC motor, so it's just two pins for going forward or reverse at full speed.

  2. The first-generation Mindstorm system had to accommodate more than motors: it also had to support sensors, so more wires were added.

  3. The "Power Functions" system didn't need to support sensors, but it did simultaneously provide raw battery positive/ground as well as PWM-controlled motor forward/reverse within a single connector.

  4. The NXT system also supplied power and ground. Instead of PWM-controlled forward/back, it had more sophisticated I2C data communication.

  5. The current generation "Powered Up" system supplies power and ground lines for simple accessories such as a simple LED. It has a pair of PWM-controlled lines to run simple motors forward/back at varying speeds. And finally, it has asynchronous serial data lines for sensors and other smart peripherals.

Seeing how it covers all the scenarios, would the "Powered Up" system be the final word in LEGO electrical connections? Or would it just be yet another standard that will soon go away? We will have to wait and see how things play out. In the meantime, we don't have to pay hundreds of dollars for LEGO sets for a taste of the LEGO life, there are many depictions of LEGO on screen in movies, TV, and video games.