Talk:Circuit Idea/Reinventing a Full-Wave Bridge Rectifier

Here is the building "scenario" that my students (group 64a) and I were using during Lab 3 to consider the popular diode circuit of full-wave bridge. Circuit-fantasist (talk) 07:18, 28 April 2008 (UTC)

Lab 3: Building a full-wave bridge circuit
Thursday, April 03, 2008, 13.45 h

Participants of this lab: Andrey Rachev, Ivelin Ivov, Ivaylo Katrazanov, Rumyana Naydenova, Sasha Madov, Miodrag Hristich, Andon Radulov, Galin Gyurov, Kamen Avramov, Dimitrina Nedelcheva, Slavka Petrova, Zdravko Georgiev, PavlinPanev 64, Ivaylo Atanasov and Miglena Nesterova.

Investigating an LED


In this exercise, we have recreated the famous circuit of full-wave bridge. In order to visualize its operation (where currents flow), we have decided to replace the ordinary rectifying diodes by LEDs with different colors. Also, we have used another LED for a load. Firstly, we have investigated the very LED to make ourselves familiar with its behavior. We have found that its performance is good for our purposes, it would shine and work without problems. It was clear that we had to connect a protecting resistor in series with the bridge circuit. PavlinPanev 64



Building the circuit on the whiteboard


Step 1. We started building the circuit on the whiteboard by connecting the load (the tested red LED). Here we assumed that DAC 1 was producing a positive voltage from 0 up to 10 V (this was the positive half-wave). Note how we have outlined the inverse S shape of the "positive" part of the future bridge. PavlinPanev 64





Step 2. Then we assumed that DAC 1 was producing a negative voltage from 0 up to -10 V (this was the negative half-wave) and connected the true S shape of the rest "negative" part of the future bridge. Only, a short-circuit turned out:( What should we do then? We began thinking... We had already known that diodes can act as decoupling elements (switches); so, we put two red-colored LEDs in the two opposite "positive" bridge legs acting as rectifying and visualizing diodes for the positive half-wave. We expected that since all the three diodes (including the "load") were connected in the same direction they would enable the current to flow in the right direction and would shine during the positive half-wave.





Step 3. But it was not sufficient...:( To remove the conflict, we had to put further two (now, green-colored) LEDs in the two opposite "negative" bridge legs acting again as rectifying and visualizing diodes for the negative half-wave. We solved the short-circuit problem; we managed to "invent" the famous full-wave bridge rectifying circuit!

You can see on the picture how we made the full wave bridge – never mind if the current flows from –  to  +  or from + to -, our red load LED will always shine! Now we can carry out a real experiment to see if our circuit will really work. PavlinPanev 64



Mounting the circuit on a prototyping PCB






This was a true hands-on exercise where we mounted the real circuit on a real prototyping PCB; we soldered the two rectifying LEDs and the LED load on the board and connected them by wires. Thus we finally got a real full-wave bridge rectifier that didn't need any measuring devices. Imagine it should indicate its state (the current direction) by the very diodes! We were eager to get to know, if it would work really as we had assumed? It would be very interesting to test it. PavlinPanev 64



Investigating the circuit by Microlab


After we supplied the circuit by Microlab system we were ready to investigate the circuit operation.



Positive input voltage


It was working as we expected - the three red LEDs were lighting when we put a positive input voltage, the other two LEDs were extinguished. Everything was OK, as we wanted to be. User:PavlinPanev 64



Negative input voltage


Then we tested the circuit at negative input voltage; again the result was excellent as we had expected. We were content with ourselves as we did our job very good. The famous full-wave bridge was working not only in theory but in real! PavlinPanev 64




 * PavlinPanev 64, thank you for your participation. Your text is very useful and informative; what you write is exactly what we need for this page. Go on developing the page in this way. Place four tildes after your insertion (they will be replaced by your user name and the date of the creation). I have also placed some photos on your user page; you have only say some words about yourself. Regards, Circuit-fantasist (talk) 05:16, 25 April 2008 (UTC)