DC filtering

[neurino]

I just ended my perfboard layout and noticed I put a cap before instead of after DC diode.

Here's the correct schematics:



and here how I cabled it:



What's going to happen? Can I leave it where it is and expect it to work as intended?

[nexekho]

If I'm looking at this correctly the diode is for polarity protection and then the capacitor bleeds noise in the power to the cap to ground... I'm not sure that it'd make a difference but it's probably better to do it the "correct" way when possible.

[anchovie]

Makes no difference to filtering, but the way you've done it leaves the capacitor unprotected from a reverse-polarity PSU, which may result in it going "bang" and smelling bad!

[Le québécois]

I don't want to take your post but the topic is the same (i think). We see in many schematic a 100 ohm resistor in serie with the +9v input prior to any thing else (ex: before the voltage divider). Is it also for DC filtering? Current limiting only?

[cpm]

I don't want to take your post but the topic is the same (i think). We see in many schematic a 100 ohm resistor in serie with the +9v input prior to any thing else (ex: before the voltage divider). Is it also for DC filtering? Current limiting only?

both. look at a RAT schematic. It has a 47 ohms in series before the cap. It forms an RC filter that improves the noise reduction, as long as current keeps low to not drop a significant voltage. It also has a reverse diode for polarity protection after this resistor, which means that in case the power is applied the wrong way, the resistor is limiting the current and avoids stressing the diode and/or the power supply
I've seen a big muff with two sequential filters of 100R+220uF.

[Le québécois]

Ok and last one! Some time the polarity protection diode is connected to ground instead of being in serie. One way better than the other? Safer in serie unless the current destroy it while to ground, it could take the current but the overload would reach the circuit?

[neurino]

But would really 9V with reverse polarity blast a 220uF 35V cap?

Is it possible, probable or sure?

(forgive me if I go back in topic...  )