Project Help Required: Car Security System

Hi there

I have designed a 433Mhz wireless controlled Car security system with door locking/unlocking facility. It is controlled by AtMega328P Microcontroller. Circuit diagram is attached. I have uploaded a basic sketch in the Atmega328 which reads the code from the 433Mhz receiver module and the locking / unlocking relays work well without Door locking motor attached. However, when I attach the locking motor, Microcontroller restarts with each relay latch. I have set the latching time for the relay as 1 second. I dont know why the system restarts and couldnt figure out where is the fault. I need help.

Initially I thought that when motor runs, the voltage drops and as a result, microcontroller resets. So I have upgraded the capacitors attached before and after to 7805 to 1000uf. This helped a little bit but still the system resets with repeated testing.

Once this problem gets solved, i have a plan to add a GSM mobile with the AtMega328 so to lock/unlock car doors using SMS. And at the end, immobilizer system controlled using GSM mobile commands.

Try to keep away the relay from the mcu lines.
Add some bypass capacitors to mcu psu,let me explain ,connect the 0.1uF and 0.01uF capacitors as close you can to VCC pins of mcu.
This should help.

Regards!

The Bypass capacitors are a rule.
THen Check LP filters.

Are you suggesting to Connect both 0.1 and 0.01 uf Capacitors in parallel together ? the circuit board is tightly made and relays are around 1.5cm away from the MCU. i'll send the picture later ...
One thing I forgot to mention that the vRef pin of AtMega328 is also connected to 5v ... is this the cause of problems or not ?
what do you mean by LP Filters?

docosama said:

Are you suggesting to Connect both 0.1 and 0.01 uf Capacitors in parallel together ? the circuit board is tightly made and relays are around 1.5cm away from the MCU. i'll send the picture later ...
One thing I forgot to mention that the vRef pin of AtMega328 is also connected to 5v ... is this the cause of problems or not ?
what do you mean by LP Filters?

Click to expand...

Yes , parallel capacitors but closely to VCC pins of mcu. This is to avoid or reduce perturbance. 1000uF for low frecuency ,it makes the VCC source smooth but it can't smooth high frecuencies that's why you add 0.1uF and 0.01uF .

There is no problem with Vref.
LP filter means Low Pass filter .

A common reason of that reset is when you turn on the relay and the contacts make a voltage spike perturbing the VCC line.
A car is a noisy enviroment for electronics.

Regards!

hi.I think the circuit which I attach here can help you .tray it and take care about Reset source in mcu.