Review Request - Car Power Antenna Driver Board
I'm needing to replace the burnt driver board of my vintage car's auto extending antenna. The antenna is triggered to extend whenever the car radio turns on, and retract whenever it turns off. This is via a 12V signal out of the back of the radio.
Rather than using a microcontroller solution, I thought I'd take some inspiration from the original driver board and build it using mostly discrete components. See the last photo for the schematic of the original circuit.
The original board used a timer to turn on the extension motor for a duration of ~12s (roughly the time it takes for the antenna to fully extend or retract), and also a PTC thermistor to detect overheating and shut off the motor.
I kept the timer idea in my circuit as a backup, but replaced the PTC thermistor with a stall current detector that shuts the motor off right when the antenna reaches an endpoint. An additional timer is used to prevent the stall detector from triggering for the duration of motor inrush current.
For simplicity and efficiency improvements, the original bjt h-bridge is replaced with a discrete mosfet h-bridge.
I know a circuit like this could be much easier implemented with a microcontroller and a modern integrated h-bridge IC, but I wanted the challenge of a discrete analog/digital design.
Please provide any suggestions to improve the simplicity of the circuit or to the pcb layout!
