# Trying to design a circuit to switch between two different capacitors

#### marcost2

Joined Nov 9, 2019
2
Hello and good morning/afternoon/evening. I was tasked to do a little full wave rectifier + 220v to 12v transformer circuit for my final proyect for my "introduction to electronics" class. We had to build the circuit with a 220v to 12 transformer, two diodes and two caps, one 100µF the other 2200µF with some way to switch between them, to be able to see the differences in Vripple between the two caps. We were told that the easiest way was to put two measure points and be done with it. But i wanted to push myself and as such i've been trying to build a circuit that isolates the two caps and makes it so that i can select which one i'm using at the moment. I have tried with NPN transistors, resistors and diodes to no avail. Im uploading a photo of the schematic of my circuit thus far, any help will be apreciated

PS: English is not my first language, feel free to correct me if i got something wrong.

#### SamR

Joined Mar 19, 2019
4,911
Welcome to AAC! Since this is homework let me start by asking what is the function of a capacitor in a rectifier?

#### marcost2

Joined Nov 9, 2019
2
Welcome to AAC! Since this is homework let me start by asking what is the function of a capacitor in a rectifier?
AFAIK, to reduce the ripple voltage, that is the voltage variations that are created as a byproduct of rectifying the sinusoide wave that is the norm for AC

#### SLK001

Joined Nov 29, 2011
1,549
Use a relay. A relay will not significantly load the signal like other devices will.

Joined Feb 20, 2016
4,368
If the specification is for 2 diodes, it is probably a center tapped transformer.
You have the polarity reversed in your circuit. Reverse the diodes, or the capacitors and LED.
Although you should be able to work this out, here is one idea.

Joined Feb 20, 2016
4,368
Now, show us the wave shape you expect across the load for each of the switch positions.

#### SamR

Joined Mar 19, 2019
4,911
to reduce the ripple voltage

OK and how does a full-wave rectifier convert AC to approximate DC?

#### Dodgydave

Joined Jun 22, 2012
11,149
Hello and good morning/afternoon/evening. I was tasked to do a little full wave rectifier + 220v to 12v transformer circuit for my final proyect for my "introduction to electronics" class. We had to build the circuit with a 220v to 12 transformer, two diodes and two caps, one 100µF the other 2200µF with some way to switch between them, to be able to see the differences in Vripple between the two caps. We were told that the easiest way was to put two measure points and be done with it. But i wanted to push myself and as such i've been trying to build a circuit that isolates the two caps and makes it so that i can select which one i'm using at the moment. I have tried with NPN transistors, resistors and diodes to no avail. Im uploading a photo of the schematic of my circuit thus far, any help will be apreciated
View attachment 190989
PS: English is not my first language, feel free to correct me if i got something wrong.
Use a Relay much easier,, also use a 470 ohm resistor instead for R1,2 resistors.