mcu halt when a Contactor is turned on

[mustafa abdalrazeq]

i have a an stm32f417vgt6 mcu and its connected with ft800 through 30 cm SPI cable

and the ft800 is driving a tft lcd .. the problem is when the mcu turn on or turn off the Contactor

the mcu halt .. can you please help me how to detect the problem and how to solve it and what couse the problem

[RomainR.]

Hello mustafa.abdalrazeq

What is the Contactor?

Do you mean it's a relay to drive power line and it is controlled by the MCU ?

Can you detail please.

BR

rrom

[mustafa abdalrazeq]

yes its a relay that used to control high power, high voltage (110-250 vac)

i forget to mention that the Contactor is driven by an on board Panasonic relay

and its isolated from the board ,, the Contactor placed 40 cm from the board

[S.Ma]

If there is no 110-250V, does the MCU stops to operate as well?

[RomainR.]

Do you have implemented Transient Voltage Suppressor Diode (on relay side) ?

What is the power source of STM32 ? Is it a MCU custom board ?

Share the schematic please.

BR

rrom

[mustafa abdalrazeq]

@S.Ma​  when there is no 110-250 volt the MCU doesn't halt

@RomainR.​  the board is custom , the power source of the a MCU is a an 12 volt acid battery that goes to buck converter then through a LDO voltage regulator

the relay side have Transient Voltage Suppressor Diode ..

in the pic the black board is the controller board the blue one is the tft controller

the Contactor is in a different place

[RomainR.]

I suspect than High voltage line 110-250VAC is routed on PCB backplane ? Can you confirm ?

What is the type of load powered by High Voltage ?

You need to add a AC filter on high voltage.

And check your decoupling capacitor circuit before and after the LDO regulator.

[mustafa abdalrazeq]

Dear @RomainR.​  i would like to thank you for your fast responds

the load may defers it may be a home or a factory it may be resistive and it may be inductive

but or tests is done without any load connected

the high volatge is routed on the top-plane (cheak the pic )

the problem start happening after we decided to separate the tft from the black board

[RomainR.]

"the problem start happening after we decided to separate the tft from the black board"

In this case, try to debug the firmware to understand where the MCU is halted in the code.

BR

rrom

[RomainR.]

Maybe interference in the flat SPI cable generated by High Voltage.

Try also to replace flat SPI wire by shielded cable and route it away from all power source (on the left from picture)

[S.Ma]

Bah, just twist the cable to make LVDS like cable.

Try to change the SPEED of the SPI GPIO and possibly put a serial resistor (1kOhm?) if really there are glitches around.

Remember that the parasitics are minimum if the electrical lines cross at 90 degrees (no crosstalk).