Hi ,
Today im facing with a problem that it happened to me twice but couldnt understand the reason behind.
Last weekend i have soldered a pcb on prototype board. The circuit contains transformer and stm32 (which is bluepill) for counting time. Transformer is 230/9v 50hz and 1.2va rating. The STM32 works great when i energies with on top programming header with stlink device. It also works with 230v . But the problem is when i apply 230v to the circuit, stm32 rtc time is jumping randomly. For example , lets say i have setted the time to 10:45 and i denergizes the circuit. After a while , when i replug the circuit to the main voltage, it jumps like 15:10. It is totaly random and this problem doent happens when i energies with programming header pins with stlink device. So the problem must be somewhere on the transformer side. The code side has no problem , i have tested many times.
This is the power supply circuit;
As you can see seconder side of the trasnformer has been regulated by lm317 . The output of the regulator is around 4.1v . There is an onboard regulator at the bluepill which is RT9193 for 3.3v regulation. So it is enough generation 3.3v power for stm32f103. At the past , i have faced that problem again but it was working with 12vdc rather than 230v. After lots of try i have figured out that the problem was belong to aluminium bulk capacitor like 470uF . When i desolder that capacitor system started to work normally. But this time , i cannot remove capacitor which is for rectification to the seconder voltage.
Im looking for a solution and idea for this situation .
Thank you.
Today im facing with a problem that it happened to me twice but couldnt understand the reason behind.
Last weekend i have soldered a pcb on prototype board. The circuit contains transformer and stm32 (which is bluepill) for counting time. Transformer is 230/9v 50hz and 1.2va rating. The STM32 works great when i energies with on top programming header with stlink device. It also works with 230v . But the problem is when i apply 230v to the circuit, stm32 rtc time is jumping randomly. For example , lets say i have setted the time to 10:45 and i denergizes the circuit. After a while , when i replug the circuit to the main voltage, it jumps like 15:10. It is totaly random and this problem doent happens when i energies with programming header pins with stlink device. So the problem must be somewhere on the transformer side. The code side has no problem , i have tested many times.
This is the power supply circuit;
As you can see seconder side of the trasnformer has been regulated by lm317 . The output of the regulator is around 4.1v . There is an onboard regulator at the bluepill which is RT9193 for 3.3v regulation. So it is enough generation 3.3v power for stm32f103. At the past , i have faced that problem again but it was working with 12vdc rather than 230v. After lots of try i have figured out that the problem was belong to aluminium bulk capacitor like 470uF . When i desolder that capacitor system started to work normally. But this time , i cannot remove capacitor which is for rectification to the seconder voltage.
Im looking for a solution and idea for this situation .
Thank you.