Circuit-symbol trainer
About this app
A card quiz on 20 circuit symbols per DIN EN 60617 — match names and auxiliary/main contact category, with terminal designations (A1/A2, 13/14, 95/96), score, streak and a filterable learning grid of all symbols.
Auxiliary and main contacts
Contactor circuits distinguish auxiliary contacts from main contacts. Auxiliary contacts switch the control circuit, such as coils and indicator lamps, and carry two-digit terminal numbers made of a sequence digit and a function digit: 1/2 means normally closed, 3/4 normally open, and 5 to 8 special functions such as time-delayed contacts. Main contacts carry the load current to the consumer and use single-digit terminals 1 to 6, odd on the supply side and even on the load side. Symbols are drawn in the de-energised, unactuated state.
What the app contains
The trainer covers 20 symbols according to DIN EN 60617 (IEC 60617), including make, break and changeover contacts, pushbuttons, a latching switch, emergency stop, contactor coil, main and auxiliary contacts, on-delay and off-delay timer contacts, the bimetal break contact of an overload relay, motor protection breaker, fuse, circuit breaker, disconnector, indicator lamp and three-phase motor. In the quiz each card asks two questions: the name, and whether it is an auxiliary or main contact. The card then shows terminals and function. Score, streak and hit rate are tracked.
Learn and practise
Learning mode shows all symbols in a grid, filterable by auxiliary, main and other components. Tapping a tile shows name, category, terminal marking and function, for example 95/96 for the break contact of an overload relay or 17/18 for an on-delay timer contact. At the end of a quiz round the app names your strongest and weakest category, so you can review in a targeted way.
Frequently asked questions
- What do terminal numbers 13/14 and 21/22 mean?
- For auxiliary contacts, the first digit is a sequence number and the second is the function digit. 13/14 is the first auxiliary contact, and 3/4 identifies a normally open contact. 21/22 is the second auxiliary contact, and 1/2 identifies a normally closed contact.
- What is the difference between a normally open and a normally closed contact?
- A normally open (make) contact is open at rest and closes when actuated. A normally closed (break) contact is closed at rest and opens when actuated. Stop buttons and interlocks use normally closed contacts, while start buttons and latching use normally open contacts.
- What does 95/96 mean in a wiring diagram?
- 95/96 is the normally closed contact of a thermal overload relay. It sits in the control circuit and opens on overload, which de-energises the contactor coil so that the contactor switches the motor off.
- How many symbols does the symbol trainer include?
- It includes 20 symbols from control engineering. You can test yourself in the quiz or browse them in learning mode as a filterable grid with terminals and function.
Subject: Electrical & Control Engineering
More from Electrical & Control Engineering
- Three-phase asynchronous motor (3D)
- A week of power
- Power contactor (3D)
- Cable decoder
- Electric arc & arc-suppression elements
- Motor protection lab
- Diagram-types explorer
- Contactor circuit simulator
A VisuApp by heyprof: interactive, free in your browser, no sign-up. What is a VisuApp? · All apps