I recently acquired a Miller 6990 kit, a fantastic toolset that includes a control arm bushing remover/installer, caster fixtures, and inclinometers with a switchbox designed for use with the DRB III scan tool for caster readings. While I don’t own a DRB III scan tool, my background in sensor technology from setting up test departments has always fueled my curiosity about automotive diagnostics and repair. My initial thought was that the sensors in this kit would operate on a standard 0-5V or 4-20 mA output, common in lab data acquisition systems. I envisioned easily connecting these signals to a simple microcontroller like an Arduino or even a voltmeter to decipher the angle from the output. However, I quickly realized these sensors are more sophisticated than anticipated. This led me to delve deeper into the workings of the DRB III tool and its sensor interface.
My exploration began by disassembling the switchbox and sensors, noting the part numbers of all visible chips. I’ve been tracing the wiring to understand the connections and signal flow. From my analysis, it appears the switchbox outputs an RS232 signal to the DRB III. This is quite manageable to interface with using most microcontrollers. It also seems the DRB III supplies 12V power to the switchbox via the cable, deviating slightly from the standard RS232 pinout but logically sound for powering external components. I haven’t yet attempted to intercept the data transmission, so I’m still unsure if the sensor data is continuously streamed or if it requires a data request from the DRB III to initiate sending. This is a key question I’m hoping someone knowledgeable about DRB scan tools, potentially even someone familiar with using a DRB scan tool in Los Angeles auto repair shops, might be able to answer. Understanding this communication protocol is crucial for moving forward.
The sensors themselves presented another layer of complexity. Although I suspect the core sensor might have a simpler output at its base, each sensor is housed in an aluminum box and mounted on a PCB, complete with its own microcontroller. Interestingly, the microcontroller is the only chip for which I haven’t been able to find a datasheet. The PCB clearly labels wire hookups as RX, TX, +, and -, strongly suggesting an RS232 serial data output. While directly accessing the raw sensor might be simpler, I’m keen to understand the existing system and avoid dismantling the sensor from its board if possible.
So, the core of my project is this: I’m reaching out to electrical engineers and anyone with in-depth knowledge of how the DRB III communicates with external sensors. My goal is to reverse engineer this setup. If we can decode the sensor communication, it would pave the way to building a compact, standalone readout device. This device would allow anyone to accurately measure caster without needing to invest in an expensive $3000 DRB III scan tool. While cheaper DRB III emulator software exists, these solutions typically lack the capability to interface with external sensors, focusing solely on software-based diagnostics. For automotive enthusiasts or smaller repair shops in areas like Los Angeles, where specialized scan tools can be a significant investment, a DIY alternative could be incredibly valuable.
If reverse engineering proves too challenging, my fallback plan is to utilize generic inclinometers and devise a mounting method for the caster brackets. However, the challenge of understanding and potentially replicating the DRB III sensor interface is a more compelling and educational side project. Plus, the necessary components are already at hand. Any insights or assistance from the community, especially those with experience with DRB scan tools in Los Angeles or similar diagnostic equipment, would be greatly appreciated.
