In the first part of this two part Instructable, we laid out a straightforward amplifier circuit on a breadboard and tested it. In this Instructable we will take those components, transplant them into stripboard or veroboard and solder them in place to create a much more robust and permanent circuit.
To make the process of building the circuit on stripboard more straightforward and less prone to error I've included an overlay image you can attach to the stripboard to guide you through the process. I have found that planning the layout and generating a printout to affix to the board has drastically reduced the number of mistakes I make.
To use the overlay, print the file at actual size. Make sure that "shrink to fit" or "fit to page" options are not ticked and scaling is set to 100%.
The stripboard layout was created in the wonderful, free tool, DIY Layout Creator. I've included the layout .diy file used so you can edit or improve the layout if you wish.
Soldering on stripboard is a little different to soldering on regular printed circuit boards. There are some useful tricks included in this Instructable to help you get tidier results and avoid short circuits.
Step 1: LET'S GET ORGANISED
If you followed the previous Instructable in this two parter and built this circuit on a breadboard you already have all of the electronic components required to build the circuit on stripboard. If not, check out that Instructable for the list of components.
In addition you will need...
- Some stripboard
- The provided overlay printed to scale and cut out
- Some solid core hookup wire
- A soldering iron and solder
- A pair of snips/side cutters and wire stripper
- A reasonably tough craft knife and a good straight cutting edge
- A trace cutter - this is just a 3.5mm drill bit. Wrap some duct tape around the blunt end for a handle. You can also use a craft knife if you're careful
Step 2: LET'S LOOK AT SOME STRIPBOARD
Stripboard, or sometimes Veroboard (this is a brand name), is incredibly useful stuff.
Take a look at your stripboard. On one side you will find strips of copper, the other side may have lines or markings on it like the picture above, or it may be bare. The side without the copper strips is the top or component side, meaning all components are inserted from this side. The copper covered side is the bottom. When components are inserted, their leads will protrude out of this side. All soldering is performed on this side
Stripboard works in a somewhat similar way to a breadboard, in that it provides you with rows of electrically connected holes into which you can insert components to build a circuit. On stripboard these copper strips are called "traces".
Unlike a breadboard, however, these traces run all the way along the board. There is no central channel to accommodate ICs. Instead we decide where the channels go, how long any particular trace should be, and whether we need or want additional traces. We do this by breaking the traces using a trace cutter or a knife.
Stripboard can be cut to size rather easily, and if you design your layouts efficiently you can make a little go a long way.
Step 3: LET'S ATTACH THE OVERLAY AND PREPARE THE STRIPBOARD
The plastic resin used in stripboard is called phenolic resin. Phenol is a useful but somewhat nasty chemical that can cause damage to your respiratory system, cause chemical skin burns and rashes and is potentially carcinogenic. When cutting stripboard it is best not to use any method that will generate airborne dust or particles, meaning saws, files and sandpaper are definitely not recommended. When cutting stripboard or cutting traces I keep a dampened tissue on hand to dab/wipe up any loose particles for disposal. Heat from soldering also causes phenol vapour to be produced, so work in a well ventilated area, preferably with a fan or solder fume extractor.
We're going to affix the overlay and our stripboard to size. The .pdf is attached on the title page along with the source .diy file if you want to make modifications and re-print. The overlay file should be colour printed at actual size, meaning scale should be 100% and "fit to page" or "shrink to fit" options should be unticked.
- Use a glue stick or spray mount to attach the overlay to the top side of a piece of stripboard. You can use a light source or the torch on your phone to help align the printout with the holes.
- To cut the stripboard to size use a durable craft knife and a cutting ruler to firmly score along a line of holes on both sides of the board. Be careful. Cut copper traces can sometimes leave a very sharp edge.
- When you have scored a line, bend the board along that line and it should snap cleanly.
- You will end up with a piece of stripboard a little larger than the print out as shown
Step 4: LET'S CUT SOME TRACES
Once the stripboard is cut to size, the first step in any stripboard project should be to make any necessary trace cuts.
- Start by locating all of the trace cuts on the overlay, they are indicated by the beige circles. Use a sharp pencil or a toothpick to poke a hole through the overlay at each trace cut
- If you turn the board around and hold it up to the light you will be able to see exactly where on each trace to make the cut
- To cut a trace, simply place the trace cutter in the hole at that point and give it a couple of twists
- Carefully check to make sure that each cut has completely broken the trace and that there are no bits of copper left bridging adjacent traces
Step 5: LET'S INSERT SOME JUMPER WIRES AND GET SOLDERING
Sometimes a stripboard layout requires us to connect traces. We'll do this using jumper wires.
The first set of photos shows where the wires will go and the second set shows how to solder them.
Soldering the jumper wires:
- Pop the jumper wire into the board where it's needed.
- If you think the wire will fall out, anchor it in place by bending the ends a little, parallel to the traces. Do not bend them perpendicular to the traces, as this can make it easier to create bridges and short circuits
- Tin your iron and solder the wire in place as you heat the trace and wire. You might need to apply heat for a little longer than you would with a regular PCB since the copper strips are relatively large.You are aiming for solder joints that look like this; Pillow shaped with the hole covered. Trim the end of the wire flush to the solder with a pair of side cutters.
Placing the wires:
- There are three jumper wires to insert, represented by the two blue lines and the green line. Poke through the overlay at each end of each wire.
- Cut some lengths of hookup wire and strip a little off the ends. It's a good idea to make the wires a little longer than the distance they are covering so you are left with a little loop of wire that you can grab onto if you need to remove them later.
- Pop each wire in and bend the ends parallel to the traces as shown to hold the wire in place.
- Once you have soldered them in
Step 6: LET'S INSERT THE FIRST COMPONENT
We'll start by inserting R1, the 10 Ohm resistor and learning another useful stripboard soldering trick.
You might have noticed in the overlay that some components are quite close together, namely C2, C3, and R1. If you think you'll need more room for your capacitors you can move R1 one or two steps to the right along its traces.
- Insert R1 as shown.
- To hold the resistor in place bend one lead flat against the board. Leave the other lead pointing straight up in the air.
- Solder the lead that you left pointing straight up. Doing this makes for a neat solder joint and helps to avoid bridges between traces.
- Now that the resistor is held in place by the soldered leg, bend the other leg straight up and solder it and trim the lead.
Step 7: LET'S INSERT THE CAPACITORS
Next we'll insert the capacitors. Make sure you are using the correct capacitors;
- C1 10uF
- C2 100uF
- C3 47nF
- C4 100uF
On the overlay, the negative leg of the electrolytic capacitors is indicated by the lighter grey mark.
- Insert C1 as shown.
- Use the same method as you did with R1 to hold the capacitor in.
- You may as well insert the other capacitors at this point.
- Solder all of the capacitors using the same technique as you did with R1.
Step 8: LET'S ADD THE AMPLIFIER IC
You can now see what the purpose of that row of four trace cuts is.
- Poke the holes for the 8 legs of the LM386 IC.
- Insert the IC the right way round, making sure that the notch on top lines up with the notch on the overlay.
- To hold the IC in place for soldering bend two pins at opposite corners inwards to clasp the board.
- Solder each pin, being extra careful not to create any bridges of solder between adjacent pins.
Step 9: LET'S DO ALL OF THE WIRING!
If you built the circuit as shown in the previous Instructable you will already have soldered wires onto the battery clip, jack socket, speaker and potentiometer and tinned the ends of those wires. If not, check that Instructable to see what to do.
We'll be soldering all four of those components into the circuit
- The red positive wire from the battery clip connects at the point marked by the red circle. The black negative wire/ground wire attaches to the ground trace at the point marked by the black circle. Insert them and solder them in place.
- The wire from the Tip and Ring of the jack socket - yellow in the photo - connects to the input signal trace at the right hand yellow circle on the left side of the board. The wire from the Sleeve connects to the ground trace at the blue circle just above.
- There are three wires from the 10K audio taper potentiometer:
- The wire from the center pin or "wiper" connects to the point marked by the orange circle on the left edge of the board.
- The wire from the counter clockwise pin - blue wire in the photo above - connects to the ground trace at the point marked by the blue circle at the edge of the board.
- The wire from the clockwise pin - yellow in the photo - connects to the signal input trace at the mpoint marked with a yellow circle at the edge of the board.
- There are two wires from the speaker. One connects to the ground trace at the blue circle on the right hand edge of the board, the other to the purple circle just below.
Step 10: LET'S CHECK FOR MISTAKES
If you have done a nice job of the soldering it should look something like this. Hang on! There's a solder bridge here! You should check your board thoroughly for any unintended solder connections between traces or bits of stray copper.
Fortunately, it's not too hard to undo a solder bridge like this.
- There's a solder bridge here between two traces that shouldn't be connected.
- To remove the bridge, melt it with your soldering iron with the tip of the iron against the phenolic int he gap between the traces.
- Drag the iron along the gap between the traces. The solder will smear along the traces, but the channel between the traces should be left clear
- The result will look like this. A little messy looking, but note that the channel is clear and the traces are no longer bridged.
You could also involve the help of some solder wick or a desolder pump, but it shouldn't be necessary unless you need to remove a component you've put in the wrong place.
Step 11: LET'S POP IT IN SOME SORT OF ENCLOSURE
Add a battery and some sort of enclosure and voila! You have just reconstituted the functional but flimsy amplifier from the breadboard onto a much more robust and permanent circuit board.
Speaker cabinet design is important for getting a speaker to sound good, so you might want to look into that!
Here I made a really simple enclosure by scoring and folding some stiff foamboard and drilling holes for the potentiometer and jack socket. The knob is a little piece of bamboo with the center drilled out. Does the job! I can turn it off by unclipping the battery at the bottom, which acts as a fastener for the bottom part of the structure.
Let us know how you do building this circuit and the beautiful enclosures you put them in!