Introduction
From home automation to industrial control, 5V dc relays are one of the most popular in switch mode power supply systems. It is relatively smaller in size and can be used in tightly closed spaces. Therefore, we have decided to write an article about 5V relays, explaining their working principles and some popular applications.
What is a 5V relay
Since the voltage applied to the relay coil is 5V, it starts a current in the coil to generate a magnetic field. The iron core becomes magnetized due to the resulting magnetic field, which further develops suction to attract the motion of the armature. The motion of the armature drives the action of the contact system, where normally open contacts close and normally closed contacts open. When voltage within the coil is cut off, the magnetic field disappears, the iron core loses its suction force, so that the armature would catch the reset spring in action and return to its original position and the contacts will return to their initial state.
The Importance of 5V Relays in Electronic Circuits
Signal isolation
During the process of electronic circuit operation, there are often different voltage levels and electric characteristics in different parts. Relays of 5V can be used as signal isolation components that isolate low voltage control circuits from high voltage or high current load circuits.
Power amplification
A relay can also drive a high-power load from the on/off condition with a very low power controlling signal, powered from 5 V voltage. In the control circuitry, only the coil driving the relay requires a small power and current supply; the contacts are able to withstand high current and high voltages for the control of high-power loads.
Logic control
5V relays can achieve complex logic control functions. By combining the contacts of multiple relays, various logic circuits can be implemented, such as AND gates, OR gates, NOT gates, etc.
Remote control
5V relay can achieve remote control function. By transmitting control signals to remote relays, control of remote devices can be achieved.
Security protection
5V relays can serve as safety protection components, promptly cutting off the circuit in case of faults or abnormal situations, and protecting the safety of equipment and personnel.
summary
5V relays play an important role in electronic circuits, as they can achieve functions such as signal isolation, power amplification, logic control, remote control, and safety protection, improving the reliability, stability, and safety of electronic circuits.
Structure composition of 5V relay
Normally, a 5V relay would have these elements:
1. The electromagnetic system includes an iron core, coil, etc. With a 5V DC voltage on the coil, a magnetic field generates and will attract the iron core to move.
2. Contact system: There's usually an open contact, a normally closed contact, and a common contact. The movement of the iron core will drive the switching of the contacts to realize the on/off control of the circuit.
The working process of 5V relay
Not powered on state
1.When no 5V voltage is applied to the relay coil, no current flows through the coil and no magnetic field is generated.
2. The armature is in its initial position under the action of the spring, at which point the normally closed contact and the common contact are closed, and the normally open contact and the common contact are disconnected.
3. Suppose the circuit enters an abnormal condition; for instance, its load is disconnected.
Power on status
1.When 5V DC voltage is supplied to the relay coil, electrons start running through the coil. According to the magnetic induction principle, each moving charged particle acts like an electromagnetic inducer around its space.
2.The iron core is magnetized, and thereby, the magnetic field increases. Due to the magnetic field, the armature is subjected to an attractive force which may be larger than the elastic force of the spring; hence, the armature moves closer to the iron core.
3. The movement of the armature drives the action of the contacts, closing the normally open contacts and the common contacts, and disconnecting the normally closed contacts and the common contacts.
At this point, the circuit state changes, such as the load being turned on.
Power outage recovery
1.When the 5V voltage on the relay coil is removed, the current in the coil disappears and the magnetic field also disappears.
2. The armature quickly returns to its initial position under the action of the spring.
3. The contacts also return to their unpowered state, with normally closed contacts and common contacts closed and normally open contacts and common contacts disconnected.
4. The circuit returns to its original state and the load is disconnected.
Common contact point classification
Normally-closed contact
The definition of a normally closed contact is: a contact in a non-powered-on relay in a closed contact state. In other words, under normal conditions, the current can pass through the circuit path where the normally closed contact is located.
Normally open contact
Definition: The normally open contact refers to a contact that, at an off-power condition of the relay, remains disconnected. In this case, the current cannot pass through the circuit path where the normally open contacts are situated. Conversion contact in the intermediate position
Composite contact point
There are three contacts involved in this type of contact group, where the middle one is a moving contact and the remaining two parts are stationary contacts. It can switch different circuit paths according to its working state of the relay.
Features of 5V relay
1.Low voltage operation: it is applied to the system that uses a 5V dc power supply. Most electronic devices and microcontroller power supply voltages match, convenient to integrate and use.
2.Smaller in size, usually compact and flexible system: Most of them are small in size, which can fit into devices when there is a space constraint.
3. Highly dependable: The normally designed and manufactured relay at 5V enjoys very high reliability and stability, which is able to work normally under various conditions.
4. Convenient for control: Relays can be driven easily by a microcontroller and logic circuits, among others, for automated control functions.
How to choose a suitable 5V relay?
Load type and current requirements
1. Determine the type of load:
The first step is to know what type of load needs to be controlled, whether it is a resistive load - for example, lighting, heating elements - an inductive load, such as motors and transformers, or a capacitive load. The changes in current and voltage during the switching of different types of loads are different, and similarly, their requirements from the relays also change.
2. Load current calculation:
According to the power and operational voltage of the load, calculate the current consumed by the load. The rated current should be higher than the load current so that the relay contacts selected could drive the load stably.
Control voltage and current
1.Confirm the control voltage
First, since the selection has to be a 5V relay, there is a need to guarantee that the control circuit can provide a stable 5V voltage. If the voltage fluctuation of the control circuit is large, it may affect the normal operation of the relay. Meanwhile, it needs to consider whether the power capacity of the control circuit can meet the current requirements of the relay coil.
2. Control current
Use the coil parameter of the relay to deduce the control current required for the coil. For the relay to be reliably operated, the current quantity coming through the control circuit should be sufficient. In general, the coil current of relay is normally rather small with values within a range of tens to hundreds milli-ampere.
Contact method and quantity
1. Selection of contact method:
Relays consist of normally open or normally closed contacts and switching contacts. The contact information should be selected according to the actual control requirements.
2. Number of contacts:
Confirm the required quantity based on the actual requirements of the control circuit. Generally speaking, for the number of contacts, relays have single contacts, double contacts, and multiple contacts. If multiple loads need to be controlled simultaneously, relays with multiple contacts can be selected.
Work environment and reliability requirements
1. Working environment:
The working environment factors of relays include temperature, humidity, vibration, dust, etc. Usually, relays that can work stably should be selected based on the specific working environment.
2. Reliability requirement assessment:
Select relays manufactured by companies that meet the reliability requirements of practical applications in terms of product quality and reliability level.
Size and installation method
1. Determine size requirements:
Determine the appropriate size based on the actual space. In most cases, relays come in three sizes: small, medium, and large. When the installation space is limited, a miniaturized type can be chosen.
2. Choose installation method:
It may include plug-in, welded, or rail mounted installation methods. The appropriate installation method should be selected according to the actual installation requirements
Summary and Suggestions
When selecting a suitable 5V DC relay, it is important to pay attention to the above points and choose according to the specifications, or consult relevant professional engineers for matching. More importantly, choose high-quality relays. QIANJI provides excellent 5V relays with guaranteed quality and reliable after-sales service. QIANJI is a relay supplier with over 20 years of experience.
