Sparky3489s Page - by Sparky3489@yahoo.com

Amplifiers, subs, enclosures and such.

VU meter project

 

As with any project, you need to get your ducks in a row.

 

Tools and Equipment required:

You’ll need some kind of circuit designing CAD program to make a schematic and layout for your board, I use EagleCAD by CadSoft

single sided is fine for this project
Don’t buy “pre-sensitized” boards; they are for transferring the image photographically.
  • PCB Etchant Solution (Ferric Chloride) - Radioshack usually has this in stock
  • Nail Polish Remover
  • Nylon Abrasive Pad - The thin green Scotch-Brite scouring pads cut into 1.5 inch squares
    (Do NOT use steel wool !!)
  • Laser Printer
  • Clothes Iron or laminator ("APACHE" model AL13P found on Amazon)
  • Hot Water
  • Latex/Rubber Gloves
  • precision finger drill or mini drill press (Model GTT-104)
  • Soldering equipment (soldering iron, solder, moist sponge, flux and the knowledge to use it all)
The Procedure:

 

Preparation

You first need to design and layout your board. Create the schematic and then the layout taking care that each component you plan to use is placed correctly and will fit with the other components in your drawings.

Order parts.

Be sure parts fit your design. I will print the schematic on my regular printer and "fit" the components to the paper and make any adjustment to the design if needed before I print to photo paper (do this with non-static sensitive parts ONLY!).

Print the Design

Print the design from a laser printer (NOT ink jet) using the darkest settings and highest resolution (e.g. Quality=Best, Intensity=Darkest, etc…). The goal is to get the greatest amount of toner onto the photo paper. Also, be sure to select “Photo Paper” or “Glossy Paper” as the paper type.

Now cut out the design around the boarder leaving about 1/8” of extra paper on three sides and 1” of extra paper on the fourth side (to grab it by).

Never touch the board part of the photo paper before or after it has been printed.

Transfer Design to Copper Board

  • Cleaning
First, you must prepare the copper board. Scrub the board with the Scotch-Brite pad in two orthogonal directions (up-and-down then side-to-side). Use a lighter pass at the end so the board is not too rough. Next, clean the board with a paper towel soaked with acetone until no more discoloration is seen on the paper towel. Press firmly and continue to use fresh parts of the paper towel.

 

Protect your skin: Use rubber gloves to when working with the acetone!

  • Ironing
Place the copper board on a flat, heat-resistant surface such as the back of wood cutting board and align the printed design face down on the copper board. Now use a clothes iron (maximum heat, no steam) to apply firm pressure to the back of the photo paper. Hold firmly like this for about 30 seconds. Now that the paper is stuck and there is no risk of slipping, go over the whole board with the tip of the iron, keeping the iron flat but torquing it forward. This should help get the toner to really stick to the copper. The whole ironing process should last about 5 minutes.

 

  • Remove Toner Treansfer Paper
After a few minutes after ironing the design on the board, you need to place the board in running water. In less than 20 seconds the paper should just slide right off. Please note the pictures below are before I discovered Toner Transfer paper so what you are seeing is paper residue from ordinary photo paper.

If things go wrong: If the toner transferred well except for a couple spots you can fill in the gaps with a resist ink pen (Sharpie). If there are more than just a few bad spots, you have the option of redoing the whole process. Just use hot water and a Scotch-Brite pad to rub off the toner and start over!

  • Etch the Board
Pour enough etchant (ferric chloride) in a flat, shallow dish placing the copper board face up in the dish so that it is just covered by a layer of the etchant. Closely monitor the progress over the next 20 minutes or so as the copper is etched away. Here are some ways to speed up the process: 

• Heat the solution in the oven or microwave to 110°F
• Jiggle the dish to provide some gentle agitation
• Gently wipe the surface of the board with a balled up paper towel as it etches

Keep if off the clothes: Be careful when working with the etchant solution. It will stain almost everything it touches! Flush it down the toilet if you have a steel sink.

Be careful not to over etch the board or your traces will begin to eat away from the side. If the whole board is etched (translucent looking) except for some stubborn spots, pull the board out of the solution and attack those spots individually. A Q-tip works well for this.

  • Remove Toner
Use the acetone and the Scotch-Brite pad to rub off the toner from all the pads and traces. Rinse the board thoroughly with hot water when you are done to get rid of the corrosive acetone residue. Now is also a good time to test for shorts and open circuits using the continuity function of your multimeter. Be prepared to do some surgery with a magnifying glass, hobby knife (for shorts), and some solder (for open circuits).

 

  • Drill Holes
Use the appropriate size bit for component placement.

 

  • Solder Components
Not much else to say for this one.

 

  • Fabricate the enclosure and make connections

 

  • Testing
Testing the assembly –

After a few adjustments -

The full monty –

 

 

Click here for other pics of putting it all together

Enjoy your new project!

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Scotch-Brite is a registered trademark of 3M corporation.

Q-TIPS is a registered trademark of Unilever.