microcontroller continously resets as i connect a 75w dc in parallel with power suppl

[osamahameed90]

i am using a DC power supply of 12v , 15A
when i connect my pic16f877a controller with power supply it works fine. when i connect 12v ,75w Dc bulb in parallel with pic16f877a controller with the same power supply , my pic16f877a controller continously resets

 

[aameer]

have you connect directly or with relay or with opto coupler

 

[paulfjujo]

hello

a lamp of 75w 12v need ~6amp in warm status,but in cold status when you just apply the power supply you can get a current spike of 5 to 10 times!
so 30amps => voltage goes down => reset !
maybe you can try to add a self in serial to reduce the spike.
or drive your lamp in progrssive PWM.

 

[T3STY]

Use a simple 5V fixed voltage regulator like 7805 to supply the MCU and it should work fine

 

[FoxyRick]

Have you properly decoupled the power supply lines with capacitors at the PIC?

 

[betwixt]

It sounds very much like you have been given the correct diagnosis. What happens is the current surge into the cold filament is momentarily dropping the 12V below the level at which the PIC's regulator can sustain it's output. There is a possible quick cure, assuming you are using a 5V regulator to power the PIC, connect a diode in series with it's input from the 12V. Then at the junction of the diode and regulator input pin, connect reservoir capacitors 100nF and 100uF in parallel to ground. You will lose about 0.6V in the diode but there should still be enough to keep the regulator happy. The diode will prevent the new capacitors from discharging back into the 12V line and hopefully will keep the PIC supply stable for long enough that the lamp surge has finished.

Brian.

 

[tpetar]

i am using a DC power supply of 12v , 15A
when i connect my pic16f877a controller with power supply it works fine. when i connect 12v ,75w Dc bulb in parallel with pic16f877a controller with the same power supply , my pic16f877a controller continously resets

Can you give more details?

Psu is switcher or linear or just trafo and Graetz bridge?

Did you use some filtering, capacitors?

Did you use 100nF close as possible to uC supply pins?

You didnt mention nothing about uC supply, how you supply uC? What is voltage regulator for uC? I hope you didnt connect uC direct on 12V.

Post circuit.