I am working on a project to replace the Bosch Alarm Siren in my car. I have attached the schematic for the device and would appreciate any feedback, corrections or comments. I have a wired prototype working in the car now, but it has shown that fly leads and push connectors are not the answer in an automotive environment.
The project takes automotive voltage (~14.8 max) to power the device and the lock and alarm signals are at the same level. I am using simple resistor dividers to reduce the signals to ~<5 volts for input into the Nano Every. VIN is through a buck convertor at 12VDC. The amplifier is turned on via a 5V gate MOSFET by supplying ground (N channel). The audio amp is using a TDA2030AL-TB51-T amp to provide the required volume. The Nano provides the tones to the amp through 2 outputs. One runs through a pot for reduced volume for the car lock/unlock tone and a second for loud tone for the theft alarm. The Nano is put to sleep after 10 minutes of no activity. External interrupt 0 wakes the Nano through the lock or alarm signal applied to D2.
Before I order the PCBs I was looking for a second pair of eyes to review the overall schematic to see if I have missed anything.
The voltage being supplied is >12 VDC (automotive charging circuit). So, I need to reduce the voltage to a Nano friendly level. The test switch will be used to test the wakeup interrupt and can also be used to trigger the locking tone so that the volume level can be set. It feeds both D2 for Interrupt 0 and when the Nano is awake D12 to cause the lock tone to sound.
I'm not worried about you using a voltage divider - quite good that you are. But it just looks odd having one half connected to the switch. The voltage will only go through it when you hit the switch, never apart from that.
Hi,
Looking at your schematic, you are doing a lot of diode logic.
Why not have each of the signals from your vehicle go straight to the Nano via potential dividers and let the software do all the logic?
It would make for a less busy PCB and cut down on components.
I've been kicking that around. I only have 2 inputs coming from the car and I want to send them both to pin 2 for Int0 wakeup and still prevent back feed from one to the other signal. As, I think about it, I can run one signal to Int0 (D2) and the other to D3 (int1) and wakeup on either. Not sure that is possible but worth a look.
The Diodes on the audio side are probably not needed as the prototype is running without them and working fine
