Recently, I decided to make a printed circuit board for my home built stereo amplifier. The stereo amplifier was built several years back using an LM4752 IC, it requires few external electronic components, runs on 10V up to 24V dc supply. See circuit below.
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Picture 1. LM4752 Audio Amplifier
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I chose to build this particular one at the time because I can easily power it with my solar panel set-up and any single 12V DC supply. I built the original on a cardboard with the component connection done with single strands of Cat 5 wire. See picture 2 below.
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| Picture 2. Stereo amplifier built on cardboard |
The sound output was not bad. Over time I have modified the original circuit to get better sound output.
'Nuff digression already…
Materials Used For The Printed Circuit Board (PCB)
1. Plain copper coated board,
2. Off the shelf (premixed) hydrochloric acid / hydrogen peroxide etching solution
3. Permanent marker.
4. Clean water in a plastic bucket (about 3 litres)
5. Plain paper for drawing
First, I drew the circuit on a piece of white paper making it bold enough to see when I flip the paper over
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Picture 3. The Circuit for the Schematic in Picture 1 (with some modifications)
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(Remember it is the circuit tracing on the flip side that you will draw on the copper coated board).
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| Picture 4. The Circuit Drawn on Copper Coated side |
This drawing will help you to determine the size of copper coated board to use. Cut out this size for your PCB.
Next, with the permanent marker, I drew the circuit as seen in Picture 4 on the cut-to-size board from the step above, you may use a rule to make straight lines. Let this dry for a couple of hours.
Now to the etching of the board.
IMPORTANT NOTICE:
v DO THIS IN A WELL VENTILATED SPACE (OUTSIDE IN THE OPEN RECOMMENDED)
v PLEASE HANDLE THE ETCHING SOLUTION WITH UTMOST CARE!
v USE GLOVES AND GOGGLES
I used a plastic container large enough to allow complete immersion of the board in the etching solution, and used twisted strands of cat 5 wire to hold the board. See Picture 5.
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| Picture 5. Copper coated board immersed in etching solution |
Immersed the copper coated board, copper coated side up, in the etching solution and moved it gently.
In about 5 minutes the exposed copper will be seen being gradually 'eaten' away. See picture 6
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| Picture 6. Partially Etched Board |
I had to interrupt the etching process when I noticed the permanent marker trace peeling off. At that point, I simply removed the board from the etching solution and wash it in the water I kept close by.
To remove the remaining unwanted copper, I had to re-draw the circuit on the board again with the permanent marker and repeat the etching process. Tracing with a better etching solution resistant material will solve this problem…any idea?
See the 'completed' board in Picture 7 below.
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| Picture 7. The ‘completely’ etched board |
After repeating the process for up to three times I decided the etching is good enough, I then used a sharp razor to cut copper areas between very close tracks away.
Afterwards, I cleaned off the marker traces that remained using premium motor spirit ( that's what I had readily available, you may use methylated spirit.
Then came drilling of holes for the electronic components on the board.
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| Picture 8. Final PCB for the Audio Amplifier |
*In my next attempt, I will find a way to make the circuit trace more resistant to the etching solution.
*I will get hydrochloric acid and hydrogen peroxide to make the etching solution with the right concentration.
