Method 1 of 4: Design
1.Have a procedure in mind before attempting the task. Remember, a good design comes first.
2.Draw the circuit schematic on either graph paper or a simulation programs such as MultiSim or Eagle CAD. The schematic should contain a detailed description of all parts, as well as easy to follow connections. Keep in mind that a basic form of the schematic will be drawn on the circuit board.
(A well-drawn schematic makes it easy to understand how a circuit works and aids in troubleshooting; a poor schematic only creates confusion. By keeping a few rules and suggestions in mind, you can draw a good schematic in no more time than it takes to draw a poor one. In this appendix we dispense advice of three varieties: general principles, rules, and hints. We have also drawn some real knee-slappers to illustrate habits to avoid.
General Principles
1.Schematics should be unambiguous. Therefore, pin numbers, parts values, polarities, etc., should be clearly labeled to avoid confusion.
2.A good schematic makes circuit functions clear. Therefore, keep functional areas distinct; don't be afraid to leave blank areas on the page, and don't try to fill the page. There are conventional ways to draw functional subunits; for instance, don't draw a differential amplifier as in Figure E1, because the function won't be easily recognized. Likewise, flip-flops are usually drawn with clock and inputs on the left, set and clear on top and bottom, and outputs on the right.
Rules
1.Wires connecting are indicated by a heavy black dot; wires crossing, but not connecting, have no dot (don't use a little half-circular ``jog''; it went out in the 1950s).
2.Four wires must not connect at a point; i.e., wires must not cross and connect.
Always use the same symbol for the same device; e.g., don't draw flip-flops in two different ways (exception: assertion-level logic symbols show each gate in two possible ways).
3.Wires and components are aligned horizontally or vertically, unless there's a good reason to do otherwise.
4.Label pin numbers on the outside of a symbol, signal names on the inside.
All parts should have values or types indicated; it's best to give all parts a label, too, e.g., R7 or IC3.
Hints
1.Identify parts immediately adjacent to the symbol, forming a distinct group giving symbol, label, and type or value.
2.In general, signals go from left to right; don't be dogmatic about this, though, if clarity is sacrificed.
3.Put positive supply voltages at the top of the page, negative at the bottom. Thus, npn transistors will usually have their emitter at the bottom, whereas pnp's will have their emitter topmost.
4.Don't attempt to bring all wires around to the supply rails, or to a common ground wire. Instead, use the ground symbol(s) and labels like +Vcc to indicate those voltages where needed.
5.It is helpful to label signals and functional blocks and show waveforms; in logic diagrams it is especially important to label signal lines, e.g., RESET' or CLK.
6.It is helpful to bring leads away from components a short distance before making connections or jogs. For example, draw transistors as in Figure E2.
7.Leave some space around circuit symbols; e.g., don't draw components or wires too close to an op-amp symbol. This keeps the drawing uncluttered and leaves room for labels, pin numbers, etc.
8.Label all boxes that aren't obvious: comparator versus op-amp, shift register versus counter, etc. Don't be afraid to invent a new symbol.
9.Use small rectangles, ovals, or circles to indicate card-edge connections, connector pins, etc. Be consistent.
10.The signal path through switches should be clear. Don't force the reader to follow wires all over the page to find out how a signal is switched.
11.Power-supply connections are normally assumed for op-amps and logic devices. However, show any unusual connections (e.g., an op-amp run from a single supply, where V- = ground) and the disposition of unused inputs.
12.It is very helpful to include a small table of IC numbers, types, and power-supply connections (pin numbers for Vcc and ground, for instance).
13.Include a title area near the bottom of the page, with name of circuit, name of instrument, by whom drawn, by whom designed or checked, date, and assembly number. Also include a revision area, with columns for revision number, date, and subject.
14.We recommend drawing schematics freehand on coarse graph paper (nonreproducing blue, 4 to 8 lines per inch) or on plain paper on top of graph paper. This is fast, and it gives very pleasing results. Use dark pencil or ink; avoid ball-point pen.
As an illustration, we've drawn a humble example (Figure E3) showing ``awful'' and ``good'' schematics of the same circuit; the former violates nearly every rule and is almost impossible to understand. See how many bad habits you can find illustrated. We've seen all of them in professionally drawn schematics! (Drawing the ``bad'' schematic was an occasion of great hilarity; we laughed ourselves silly.)
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3.If a simulation program is being used, test the circuit thoroughly in the simulated environment. If no simulation program is used, assemble and test one or more prototypes of the circuit on a breadboard. Breadboards are very easy to use, and allow one to view the results of a circuit in real time without the need for solder or permanent etches.
4.Make sure the circuit functions on the breadboard, or in the simulation software.
Method 2 of 4: Drawing
1.Acquire a circuit board. Circuit boards are about a dollar apiece, and are simply a layer of copper over an insulator. The typical size is usually 3.5 inches by 5 inches. Drawing is simple; all that is required is an indelible marker, such as a Sharpie. A ruler is also helpful.
2.Draw out your circuit on your board with the Sharpie. Keep in mind that copper cannot be between components, for example, if connecting an LED, there must be a gap in the copper between the positive and negative points of connectivity. Without a gap, the electricity would flow around the LED, as opposed to through it. Remember laws of electricity, all circuits must end at either a negative or ground, or no current will flow.
3.Use thin lines, but lay the ink on thick, it is important that the copper is dissolved before the ink, and that there are no thin patches in the ink exposing copper.
Method 3 of 4: Etching
• A non-metallic basin that is deep enough to submerge the circuit board
• Non-metallic containers for mixing
• Goggles
• Vinyl or Latex gloves
• A device used to agitate the circuit board (a stick)
• Hydrochloric Acid (Muriatic Acid)
• Hydrogen Peroxide
• Rubbing alcohol
• Acetone or mineral spirits
1.Put on the goggles and gloves. Always remember safety first.
2.Make sure the area is well ventilated before mixing. The chemicals will produce hazardous fumes.
3.Mix two parts hydrogen peroxide for every one part hydrochloric acid. When mixed, they form a substance that is a severe skin irritant, and will produce toxic chlorine gas.
4.In a non-metallic basin pour enough of the solution to completely submerge the circuit board.
5.Drop in the circuit board and agitate it for about ten to fifteen minutes. Continue stirring until all copper has dissolved, and the solution has taken on a slight green tinge.
6.For cleanup, make sure you are wearing gloves. Wash the board off in cold water to remove any etching solution. Then use a paper towel or rag to dry it off completely. Set it aside. Assure that there is no solution in the workspace or containers then remove the gloves and goggles.
7.Mix a one to one ratio of acetone and rubbing alcohol. Take a paper towel, dip it into the solution, and gently rub it over the surface of the board. The permanent marker will begin to come off. Continue rubbing until all marker is gone. You should see that your circuit is now inscribed in the copper.
Method 4 of 4: Assembly
• Hand-held Drill or Drill Press
• Various drill bits
• Soldering iron
• Solder
1.Before drilling locate all the positions of the through-hole components. Copper dust is toxic, wear a dust mask.
2.Drill through the board with a bit wide enough to accommodate whatever part must be placed at that location. Remember not to make the hole to wide, or soldering will be very difficult.
3.Place the components on to the circuit board at their designated locations. Gently bend the legs of the component against the underside of the board, to hold the part in place. Make sure parts with polarity are lined up correctly with the corresponding positive and negative. Check and double-check the location of all parts before soldering.
4.Soldering is a skill that requires practice, although it is not inherently difficult.
(Mainly deals with the soldering of through-hole components into printed circuit boards (PCBs). Through-hole components are those which have leads (meaning wires or tabs) that pass through a hole in the board and are soldered to the pad (an area with metal plating) around the hole. The hole may be plated through or not.
Soldering of other electrical items such as wires, lugs, have slightly different steps but the general principles are the same.
Steps:
1.Select the correct component. Many components look similar, so read the labels or check the color code carefully.
2.Bend leads correctly if required, discuss stress relief. To be completed...
3.Clinching leads. Discuss whether to cut leads before or after soldering based on whether heatsinking effect is required. To be completed... 
4.Melt a small blob of solder on end of the soldering iron. This will be used to improve the transfer of heat to your work.
5.Carefully place the tip (with the blob) onto the interface of the lead and pad. The tip or blob must touch both the lead and the pad. The tip/blob should not be touching the nonmetallic pad area of the PCB (i.e the fibreglass area) as this area can be damaged by excessive heat. This should now heat the work area.
6."Feed" the solder onto the interface between the pad and lead. Do not feed the solder onto the tip! The lead and pad should be heated enough for the solder to melt on it (see previous step). If the solder does not melt onto the area, the most likely cause is insufficient heat has been transferred to it. The molten solder should "cling" to the pad and lead together by way of surface tension This is commonly referred to as wetting.
•with practice, you will learn how to heat the joint more efficiently with the way you hold the iron onto the work
•flux from the solder wire is only active for about one second maximum after melting onto the joint as it is slowly "burnt off" by heat
•solder will wet a surface only if:
•the surface is sufficiently heated and
•there is sufficient flux present to remove oxidation from the surface and
•the surface is clean and free of grease, dirt etc.
7.The solder should by itself, "run around" and fill in the interface. Stop feeding the solder when the correct amount of solder has been added the the joint. The correct amount of solder is determined by:
•for non plated through hole (non-PTH) PCBs (most home made PCBs are of this type) - stop feeding when the solder forms a flat fillet
•for plated through hole (PTH) PCBs (most commercially manufactured PCBs) - stop feeding when a solid concave fillet can be seen
•too much solder will form a "bulbous" joint with a convex shape
•too little solder will form a "very concave" joint.)
5.Test your circuit board before installing it into its permanent location. Use a multimeter, if possible, to diagnose connection problems. A De-soldering gun can be used to make minor switches and repairs.
Tips
•If MultiSim is too expensive, or not available, a good free program is PCBExpress or Eagle CAD's free version.
•Do not look directly over your etching basin, or you will inhale toxic gas.
•Circuit boards are relatively cheap. There is a probability that you will make a mistake, so buy enough to work with and make batches of two or more.
•Muriatic (hydrochloric) acid can usually be acquired at a hardware store or pool store.
•Remember that the circuit board can take up to twenty minutes to etch without agitation, but as little as seven with agitation
•For large, complicated boards or large batches a drill press is more reliable and really speeds up the work.
Warnings
•Copper dust is toxic, wear a dust mask to prevent inhalation.
•The hydrochloric acid you are using is concentrated (12 molar), take care not to spill any on your skin, as it will cause SEVERE chemical burns.
•The etching solution is very dangerous, so always wear your gloves and goggles, and always work in an open area.
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