{"id":52263,"date":"2026-11-01T10:50:48","date_gmt":"2026-11-01T10:50:48","guid":{"rendered":"http:\/\/siratek.net\/index.php\/tutorials\/identifying-components\/"},"modified":"2026-11-01T10:50:48","modified_gmt":"2026-11-01T10:50:48","slug":"identifying-components","status":"publish","type":"siratek_tutorial","link":"https:\/\/siratek.net\/index.php\/tutorials\/identifying-components\/","title":{"rendered":"Identifying Components"},"content":{"rendered":"

<\/p>\n

What this covers<\/h2>\n

A kit arrives as a bag of small objects, most of them unlabelled in any obvious way. This is how to work out what each one is and which way round it goes.<\/p>\n

Getting this wrong is the usual way a beginner destroys a part, and it is entirely avoidable.<\/p>\n

Before you begin<\/h2>\n

Nothing to wire. Have your components to hand, and good light. A multimeter helps for the last section but is not needed for the rest.<\/p>\n

Resistors<\/h2>\n

Small, usually beige or blue, with a wire at each end and coloured bands around the body. They have no polarity, so either way round is fine.<\/p>\n

The bands give the value. Hold the resistor with the lone band, usually gold or silver, on the right<\/strong>, then read from the left.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Colour<\/th>\nDigit<\/th>\nAs a multiplier<\/th>\n<\/tr>\n<\/thead>\n
Black<\/td>\n0<\/td>\nx 1<\/td>\n<\/tr>\n
Brown<\/td>\n1<\/td>\nx 10<\/td>\n<\/tr>\n
Red<\/td>\n2<\/td>\nx 100<\/td>\n<\/tr>\n
Orange<\/td>\n3<\/td>\nx 1,000<\/td>\n<\/tr>\n
Yellow<\/td>\n4<\/td>\nx 10,000<\/td>\n<\/tr>\n
Green<\/td>\n5<\/td>\nx 100,000<\/td>\n<\/tr>\n
Blue<\/td>\n6<\/td>\nx 1,000,000<\/td>\n<\/tr>\n
Violet<\/td>\n7<\/td>\n<\/td>\n<\/tr>\n
Grey<\/td>\n8<\/td>\n<\/td>\n<\/tr>\n
White<\/td>\n9<\/td>\n<\/td>\n<\/tr>\n
Gold<\/td>\n<\/td>\ntolerance, 5 percent<\/td>\n<\/tr>\n
Silver<\/td>\n<\/td>\ntolerance, 10 percent<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

On a four-band resistor the first two bands are digits, the third is the multiplier and the fourth is tolerance. Red, red, brown, gold is 2, 2, times 10, which is 220 ohms<\/strong>: the one in nearly every LED circuit.<\/p>\n

Five-band resistors use three digits then a multiplier. Brown, black, black, red, brown is 1, 0, 0, times 100, which is 10 kilohms<\/strong>.<\/p>\n

Two honest warnings. Brown, red and orange are genuinely hard to tell apart under poor light, and on blue-bodied resistors red and orange look almost identical. And a resistor can be read from either end, giving two different answers. If the value you read seems odd for the circuit, turn it round and read it again. When it matters, measure it.<\/p>\n

\"Resistor
Three digits or four colours say the same thing: two figures, then the zeros.<\/figcaption><\/figure>\n

Surface-mount resistors<\/h2>\n

The tiny black rectangles on module boards are marked with numbers instead of colours. The first digits are the value and the last is how many zeros follow.<\/p>\n

    \n
  • 103<\/code> is 10 followed by 3 zeros, which is 10,000 ohms<\/strong>, or 10 k.<\/li>\n
  • 221<\/code> is 22 followed by 1 zero: 220 ohms<\/strong>.<\/li>\n
  • 472<\/code> is 47 followed by 2 zeros: 4,700 ohms<\/strong>, or 4.7 k.<\/li>\n
  • 000<\/code> or 0<\/code> is a link, zero ohms, used as a jumper.<\/li>\n<\/ul>\n

    This is worth knowing because it lets you read a module before trusting it. The 103<\/code> on the DHT11 board is the pull-up resistor that tutorial says you do not need to add; the markings beside each LED on the traffic light module are its current-limiting resistors.<\/p>\n

    LEDs<\/h2>\n

    Clear or coloured plastic, two legs of different lengths.<\/p>\n

      \n
    • The longer leg<\/strong> is the anode, the positive side.<\/li>\n
    • The shorter leg<\/strong> is the cathode, and goes to ground.<\/li>\n
    • The rim has a flat spot<\/strong> on the cathode side. Trust this over leg length, because legs get trimmed.<\/li>\n<\/ul>\n

      An LED fitted backwards does not light and is not damaged. An LED fitted without a series resistor is damaged immediately. Of the two mistakes, only one costs you a part.<\/p>\n

      Capacitors<\/h2>\n

      Two kinds turn up in beginner kits, and they differ in the one way that matters.<\/p>\n

      Ceramic<\/strong>, small orange or blue discs, no polarity, marked with a three-digit code read in picofarads the same way as surface-mount resistors. 104<\/code> is 100,000 pF, which is 100 nF, the common decoupling value.<\/p>\n

      Electrolytic<\/strong>, small cylinders, usually black or blue, with the value printed plainly such as 100uF 25V<\/code>. These do<\/strong> have polarity. The negative leg is shorter and the body carries a stripe marked with minus signs down that side.<\/p>\n

      An electrolytic fitted backwards may survive, may fail quietly, or may burst. Always check the stripe. Note also the voltage rating: a 6.3 V capacitor on a 12 V supply will fail.<\/p>\n

      Transistors and voltage regulators<\/h2>\n

      Both are small black semicircular or rectangular packages with three legs, and they look very similar. The printing on the flat face is the only way to tell them apart, and it is small.<\/p>\n

      Common markings in these kits: 2N2222<\/code>, BC547<\/code> and S8050<\/code> are transistors; 7805<\/code> and AMS1117<\/code> are voltage regulators. Pin order differs between types and cannot be guessed, so look up the part number before wiring one.<\/p>\n

      If the printing is worn away, the part is not worth the risk. Put it aside.<\/p>\n

      Diodes<\/h2>\n

      Small glass or black cylinders with a band at one end<\/strong>. That band marks the cathode, the end current flows towards. Diodes only conduct one way, which is the point of them, so the band is not optional information.<\/p>\n

      1N4007<\/code> is the common power diode and 1N4148<\/code> the common small-signal one.<\/p>\n

      Modules<\/h2>\n

      Anything on its own small circuit board is a module, and these are the easiest of all, because the pins are labelled on the board itself.<\/p>\n

      Read the silkscreen. VCC<\/code> or +<\/code> is power, GND<\/code> or -<\/code> is ground, and the rest are signals, usually named for what they do: DO<\/code> for a digital output, AO<\/code> for an analog one, SDA<\/code> and SCL<\/code> for I2C, TRIG<\/code> and ECHO<\/code> on the ultrasonic sensor.<\/p>\n

      Two things to remember. The header can usually be fitted either way round, so read the label rather than counting positions. And VCC<\/code> means the voltage this module wants<\/em>, which is not always 5 V.<\/p>\n

      Check yourself<\/h2>\n
        \n
      1. Red, red, brown, gold. What value?<\/li>\n
      2. An SMD part marked 472<\/code>. What value?<\/li>\n
      3. Which LED leg goes to ground, and what is the more reliable sign?<\/li>\n
      4. You find a cylinder with a stripe down one side. What are you being told?<\/li>\n<\/ol>\n

        Answers in order: 220 ohms. 4.7 kilohms. The shorter one, and the flat on the rim is more reliable than leg length. That it is polarised, and the striped side is negative.<\/p>\n

        Troubleshooting<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n
        Symptom<\/th>\nLikely cause<\/th>\nCheck or fix<\/th>\n<\/tr>\n<\/thead>\n
        Two readings from one resistor<\/td>\nRead from the wrong end<\/td>\nThe tolerance band goes on the right<\/td>\n<\/tr>\n
        Cannot tell brown from red<\/td>\nPoor light, or a blue body<\/td>\nMeasure it with a meter<\/td>\n<\/tr>\n
        LED does not light<\/td>\nFitted backwards<\/td>\nFlat on the rim goes to ground<\/td>\n<\/tr>\n
        Capacitor got hot or burst<\/td>\nElectrolytic fitted backwards<\/td>\nCheck the stripe before fitting<\/td>\n<\/tr>\n
        Transistor does nothing<\/td>\nPin order assumed<\/td>\nLook up the part number<\/td>\n<\/tr>\n
        Module reads nothing<\/td>\nWired by position, not by label<\/td>\nRead the silkscreen<\/td>\n<\/tr>\n
        Module runs hot<\/td>\n3.3 V part on 5 V<\/td>\nCheck what VCC<\/code> means for that board<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Next steps<\/h2>\n
          \n
        • Easier first:<\/strong> Voltage, Current and Resistance<\/em>.<\/li>\n
        • Next:<\/strong> Using a Breadboard<\/em>, where these parts get connected together.<\/li>\n
        • Related product:<\/strong> a digital multimeter, which settles every doubt on this page in seconds.<\/li>\n<\/ul>\n

          Sources and attribution<\/h2>\n

          All text in this tutorial is original Siratek work.<\/p>\n

            \n
          • Resistor and capacitor marking schemes are the standard published codes.<\/li>\n
          • Part numbers are given as examples of what commonly appears in these kits, and any specific part should be confirmed against its own datasheet.<\/li>\n<\/ul>\n

            No third-party tutorial text, diagrams, photographs or code has been reproduced here.<\/p>\n

            <\/p>\n<\/body>","protected":false},"excerpt":{"rendered":"

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