isolationpcb-design
Below picture is the rectifier section of design on the PCB:
The space between AC and DC voltage is ~2 cm, except at the bottom that I put four M3 holes which I'm going to drill and connect them to each other.
The relay control part is going to connect to an opto-isolator and from there to the MCU.
Is the taken precaution steps enough for isolating AC from DC? any tips for improvement?
There is no one single strategy, and I don't think you can expect to get the design absolutely right without some trial and error.
Some blocks may need buffering from others. It is common to minimise external influence on the LO, and that often means a buffer between it and the mixer. An emitter follower (or source follower with a FET) running at fairly high current (10-20ma rather than 1-2ma) for good linearity may be called for.
Other times you may simply need to impedance-match between stages, using the "maximum power transfer theorem" (loosely stated, make source and load impedances equal) to minimise added noise by using as much of the source power as possible. This would apply between antenna and input filters, between these and RF amplifier, between mixer and IF amplifier etc, i.e. before the gain stages where signal levels are smallest.
For this reason a lot of RF circuits standardise on specific impedances (50 ohms is commonest, but also 75 ohms, 300 ohms or 200 ohms).
Sometimes you need to match circuits with different impedances. Then you can:
You will see all these techniques employed.
I recommend drawing the slot in the footprint. Perhaps creating two versions of the part.
With and without (only larger hole). Since plated slots are a paid extra with most PCB manufacturers that might not be necessary for some prototypes.
To do this, draw the slot on the dimension (20) or milling (46). Which does not matter, unless your fab house explicitly asks for plated slots to be a separate layer.
Dimension will be guaranteed to be outputted to Gerber and sent to the fab house, milling is not.
To make a slot plated, simply put copper right to or over the slot on both layers.
The slot is probably not visible on your board since either you didn't update the library in the project, or layer Milling (46) is not visible.
In eagle, it will never show as slot pads layer, contrary to other packages that natively support a plated slot pin.
An example is the POWER_JACK_SLOT and POWER_JACK_PTH in Sparkfun_Connectors.
The difference between the two variants in the Sparkfun library is the milling layer within in the green pad. Pads layer (17) is also copper, except on all layers. This means the slot is already surrounded with Pads layer, thus copper.
The crosshair is the drill mark on Holes (45) or Drills (44) layer, that is visible on any drill hole.
(if those layers are active)
Best Answer
If you want it safe, most likely not.
When you have AC Line and low voltage on the same board, you need to have a clear separation of the two sections. Here it is not the case.
The AC side and the low voltage side need to be isolated from each other, and from the circuit, it seems not to be the case. You need to have optical or galvanic isolator between the two sides.
It is recommended to use cutout through the board to separate the section and without having any trace going to either section. This has several advantages from having a clear boundary, to avoid having PCB defect that might short AC to the low voltage side.
Few example: