Some components have particular features that we can emphasise clearly in our diagrams by using graphics. Regulators are easily destroyed by wrongly connecting them so it’s vital that the circuit diagram is clear in this respect. Regulators usually have three terminals, Input, Output and Ground (or adjust), which are clearly labelled on our circuit diagrams. terminal (pin 4) might be shown with the letters “ nc” – it's to give you confidence that there’s no connection: it’s been left as a “floating” pin. The device's data sheet would explain the functions of each pin. The positive supply rail is +9V and the 0V rail is also shown. in a demo circuit with its pins numbered as shown. Integrated circuit connections are only identified by their pin-numbering sequence, and to mis-interpret them could be disastrous, so check the circuit diagrams closely.

However you’ll generally need to identify them yourself in circuit schematics. MOSFET transistors (n-channel or p-channel) have three terminals – drain (d), gate (g) and source (s) which again we show clearly in our own circuit diagrams to help beginners. Furthermore, we clearly show the transistor pinouts in all our drawings, removing any scope for connecting them wrongly! Something to look for is the arrowhead in the transistor symbol: it denotes the emitter but sometimes in data sheets etc it might not be drawn too clearly.

Transistors: bipolar (NPN or PNP) transistors have an emitter (e), base (b) and collector (c): at EPE Magazine we show these letters on our circuit diagrams, but usually you won’t see them in manufacturer’s diagrams. Both variations of symbols are shown (EN/ DIN/ BS and ANSI). Generally you’ll need to read the circuit diagram carefully to identify the pins.Įlectrolytic capacitors: it can be highly dangerous to reverse-connect them so the polarity is always clearly marked in circuit diagrams, with a + sign showing the most positive connection.

Thyristors have terminals of anode (a), cathode (k) and gate (g), and triacs have a main terminal 1 (MT1), main terminal 2 (MT2) and gate (g) which we show clearly in our own circuit diagrams. This applies to diodes, rectifiers, LEDs, Zener and Schotkky diodes, bridge rectifiers, etc. Previously we used a + sign (only) to mark the cathode. Usually we mark the cathode with a ‘k’ and the anode with ‘a’. How to read circuit diagrams (Part 2) - component specific aspectsĬertain components are polarity-sensitive, so it matters a lot which way round they’re connected: some parts will be destroyed if improperly connected so the circuit diagram will always show the correct orientation.ĭiodes and rectifiers: these are the most common polarised components.

Free hobby electronics circuit diagram