Isolation in the pcb

[2bengg]

the main inputs will be 230v ac .

This is going to be an approximate block diagram of my pcb.
the rectifier will basically be a step down + bridge + 5v regulator like 7805.

what i would like to know is, will the micro controller be safe ? or would i need to add additional protection ? if so, what ?

would there be any other better way to achieve this ?

 

[tpetar]

If you use transformer and well designed psu with voltage regulation for uC, all is ok.

 

[2bengg]

what do you mean by well designed psu ? do you mean buy a psu ?
i was hoping to make it myself, with some of the components i mentioned.
transformer for stepdown.
bridge for ac - dc
with filter circuit having a capactior and resistor.
this fed to 7805 for.
output of 7805 fed into micro controller.

would this be considered a good design ?

 

[tpetar]

what do you mean by well designed psu ? do you mean buy a psu ?
i was hoping to make it myself, with some of the components i mentioned.
transformer for stepdown.
bridge for ac - dc
with filter circuit having a capactior and resistor.
this fed to 7805 for.
output of 7805 fed into micro controller.

would this be considered a good design ?

I mean on properly designed psu: transformer, Graetz bridge, proper capacitors, voltage regulator section, no high ripple or spikes on output,... I hope you will not use transformeless psu .

 

[2bengg]

aah i get it now.
thanks

 

[123jack]

A basic supply can work ok - it depends what you are designing for.
Even if its just a lash up for your own use you'll possibly want a fuse - perhaps a zenner circuit to blow it at least.
(quick cheap and simple)
Remember the current and voltage capacity of the track or board you use and whether or not you need to ground anything.
You might also want some sleeving for the transformer wires and dont forget to overspecify a little.
Also remember 7805's can come with different capabilities and whether you need heatsinks.
You seem to know the basic idea but its always good to ask. Read the 7805 datasheet too.
If in doubt yahoo PSU and look at what others have done similar to your own project but dont trust
anything blindly.

 

[davoud]

I think your scheme is good however coupler is no need and just a transistor can operate safely because relay separate AC line and regulated 5v voltage

 

[andre_luis]

Not a good choice to use the same 5V bus than the one which supplies uC, due to induced spike can resset it.


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