While the Citroën logo they project onto the pavement looks great, [OrangeTungsten] wasn’t thrilled with how their door-mounted projectors actually functioned. The mechanism for detecting when they should kick on was a bit too clever for its own good, and needed to be simplified a bit. Luckily for us, the process was meticulously documented for anyone else who might find themselves in a similar situation.
Originally, the projector detected when it should turn on by sensing the presence of a tiny magnet using a Hall effect sensor. There are certainly some advantages to this approach, but in practice, [OrangeTungsten] says the retrofitted magnet would keep falling off and leaving the projector inoperative. The fix was simple enough: figure out how the circuit worked, pull out the Hall effect sensor, and replace it with a simple button that would physically make contact with the door frame.
It’s not a terribly complex fix, but it’s a clever solution and well documented, and that goes pretty far around these parts. We were also interested in this one because an examination of the electronics inside the projector uncovered a 8-pin microcontroller — the sole purpose of which would appear to be polling the Hall effect sensor and using its status to throw a transistor which in turn powers the LED.
It’s hard to believe that whoever designed this gadget couldn’t figure out how to turn an LED on and off without a MCU, but we’re living in strange times. We assume there’s some kind of justification for this, such as some flashing or fading effects, but [OrangeTungsten] never mentions the things doing anything more complex than simply turning on and off.
Whatever the rationale was behind the original design of these projectors, the important thing is that the application of some hardware from the parts bin got them up and working again, which is something we never get tired of seeing.
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Facts Only
* A projector's mechanism detected activation by sensing a tiny magnet using a Hall effect sensor.
* The retrofitted magnet was reported to cause the projector to inoperative.
* The fix involved replacing the Hall effect sensor with a button that physically contacted the door frame.
* The internal electronics included an 8-pin microcontroller responsible for polling the Hall effect sensor status to control a transistor powering the LED.
* This setup suggests the microcontroller was used to manage the on/off function based on the sensor reading.
Executive Summary
Full Take
The narrative presents a tension between sophisticated design and practical, low-level engineering solutions. The observation that an 8-pin microcontroller was used solely to poll a sensor and control a transistor suggests either a deliberate architectural choice for future flexibility or an instance where available components dictated the simplest path to function. The reflection on the rationale behind this design touches upon the tension between intended complexity and actual implementation, noting that the functional outcome—getting the hardware working using readily available components—is prioritized over the original, potentially complex intent. This mirrors a broader theme in technology where functional reality often diverges from idealized blueprints, driven by constraints of material availability rather than pure theoretical optimization. The implication is that agency in design can be partially restored when pragmatic engineering overrides conceptual ambition.
Bridge Questions: What are the non-functional aesthetic or interactive possibilities that the original designers might have envisioned for this system? How does the ease of repair, as demonstrated here, change the perceived value of embedded versus external complexity in consumer electronics? Is the focus on what *can* be done with scavenged parts a critique of modern design practices, or simply an acknowledgment of iterative engineering history?