In smart systems, you obviously cannot avoid switching devices. In this tutorial, we want to explain the basics of relay circuits and, of course, support this with exciting examples from our system. How about emergency lighting, for example, if the battery fails? ?
Relays (or. relay → we only use the English term) are basically nothing other than remotely operated switches. The working circuit is closed via a control circuit. The whole thing works via an electromagnetic field (coil) and an armature, which operates the actual switch. This is therefore a mechanical component that "wears out". That's why we only use high-quality Omron relays on our circuit boards to guarantee you a long service life. It would be stupid if you were suddenly no longer able to switch the lights or pumps while you were out and about.
But what do we need to consider now?
Hot or decoupled relays?
Our relays are decoupled from the working circuit to the control circuit. This has the advantage that we can switch "any" voltage via these relays. We can therefore switch our 230V devices, 12V consumers or control signals. With so-called "HOT" relays, for example, we would switch 12V to the relay. When switched, 12V is therefore available for the consumer. This makes sense in some cases, but not in our case. The connector plug on the relay board would have to be much larger to handle all the current and we would be very limited in the circuit options.
Normally Open VS Normally Closed
We use 4x NC/NO and 4x NO relays on the relay board. But why two different ones? As the name suggests, "normally open" relays are open when de-energized. We therefore have to apply power to switch them. In most cases, this is completely sufficient to switch lamps, pumps, etc. But what can we do with "normally open and normally closed" relays? We have 3 contacts there. The middle one is our "COM" port and is always in contact with exactly a the other pins. Once to the "normally closed" contact in the de-energized state and to the "normally open" contact in the switched state.
What can this be used for?
This can be used, for example, to switch valves in two directions. The control line is placed on the "COM" port and the other two contacts are used for the open and closed commands. Or you could build a kind of emergency light. Because we know that when there is no power, we have a connection via the "normally closed" contact. If the main battery fails and with it the VanPI, you could then activate a small emergency light via this contact using the starter battery. (In the VanPi system, the relay must be permanently activated, otherwise the light will come on.) With these NC/NO relays, you have a bit more flexibility in terms of options.
Electricity and security?
Since we can apply any voltage, we naturally also have to pay attention to the protection in our circuit. As we learned above, relays are simply remote-controlled switches.
Our relays are designed for a current of 10A designed. That is enough for most consumers in the camping sector. A short-term higher current is negligible here. What is not so good for the relays are sparks at high starting currents. For example, large refrigerators or motors have a very high starting current, which can lead to a spark in the relay. In the long term, this then leads to the contacts melting. It is the same with larger consumers over 10A. Here you have to add a larger relay. In the automotive sector, however, you can find cheap components that can easily switch 40A. The relay on the VanPi system is then only used to switch the larger relay. Examples of applications are boilers and small electric heaters.
If the 8 relays on the relay board are not enough for you, you can easily add relays via WiFi. There is already a tutorial for this on our website:
