How Linear Actuator Circuits Work

In order to generate linear motion, in mechanics and robotics, affordable and simple to operate devices called linear actuators are most commonly used. Their moving capabilities can depend on different mechanical/electro principles: pneumatics, hydraulics, and voltage. The latter type of actuators is the most compact and accessible. Robotics enthusiasts highlight the utter simplicity of connecting such actuators to the system’s electrical equipment.

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Electrical linear actuators cannot operate in a proprietary manner (like, for instance, hydraulic devices, the performance of which is based on the heat linear expansion of the working body – machine oil, usually) – they require certain control system. This fact opens wide prospects of implementing an electric linear actuator domestically. In general, these tools serve as a part of a certain system, setting its separate elements in motion. Thus, you can build automatic gates, elements controlling an automated opening and closing of hatches, and many other useful things with the help of linear actuators. In order to provide their correct performance, one should initially draw a blueprint of some kind where general connections and functional elements of the mechanism-to-build are defined. Let’s continue discussing the topic further through the article, shall we?

Linear Actuators: Recalling Principles of Operation

In the foundation of any electric linear actuator, there is an ordinary electric motor. It can be either of DС (direct-current) type or AC (alternate-current) type. The DC-powered option is the most commonly used one. The mechanism of a linear actuator converts the rotary capabilities of a motor to the subsequent straight motion of the main actuator’s mechanism. For this purpose, all in all, a linear actuator feature:

  • – DC motor;
  • – basic actuator;

These are integrated into a single mechanism due to quite compact dimensions and can create linear motion when assembled. Notice also that actuators have an automatic shut-off feature: in case of power failure, a tool will freeze in a fixed position.

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In order to manage the system based on a linear actuator, you will need a control unit. Its main purpose is to implement three basic operations: the launch of an actuator’s up and forward motion; the launch of an actuator’s down and backward motion (also called reversible motion); and stop (i.e., cease of motion in any direction).

According to practice, industrial systems of automatic motion management are extremely expensive and many enthusiastic amateur mechanics consider such prices absolutely unreasonable. The thing is, the mechanism’s implementation single-handedly requires neither much effort nor huge expenses.

Minimum Set of Components for the Remote Management System

Before planning the blueprint, let’s define a basic set of components required for the implementation of a remote control system based on linear actuators. Keep in mind that while forming a blueprint, you may realize the need in some additional components (that’s the practical use of an initial blueprint or scheme).

Thus, the linear-type automation package usually includes:

  • – a required number of linear actuator devices;
  • – a control unit;
  • – indicating lights;
  • – a transmitter with the built-in antenna;
  • – a remote control device;

All of these components will surely be required to interconnect with each other in a certain manner. For each separate case, the connection principle can be different (which must be reflected in the scheme). We’ll talk about it in the following paragraph.

Major Rules of Composing and Reading Schemes

Generally speaking, an electrical scheme is a blueprint that defines the full stack of elements and connections between them, and that also provides a detailed image of the device’s work principles. Such scheme visualizes all the electric elements or devices required for the implementation and control of the equipment’s set electric processes, all the electrical connections between them, as well as electric elements on edges of input and output circuits. Moreover, blueprints allow displaying connecting and mounting elements installed alongside the device for constructive reasons.

Here’s a general legend you can use for your potential blueprint:

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Building A Linear Actuator-Based Circuit

Now, let’s define the major rules of building linear actuator-based circuits:

  1. – First of all, subdivide your future operating device into functional parts: power; interlock circuit; final input devices and signal routing to the decision-making device; final output devices and signal routing from the decision-making device to them; the decision-making device itself and data exchange with other equipment. The best way is to visualize these parts on separate blueprint sheets;
  2. – The circuit signal direction must always be left to right. I.e., final input devices must be located in the left part of the circuit, while final output devices in the right part (this goes for every other separate element);
  3. – the current in such circuits must always flow top-to-bottom. I.e., the upper part of the circuit must correspond to the large voltage potential (this rule also goes for every other element);
  4. – There’s no need in overloading the circuit with connecting wires.  Your main goal is to implement the routing of input data signals to the decision-making device (or from the decision-making device to the executing end devices);
  5. – Pro-Tip: you can visualize some less significant parts of the circuit for improved readability by defining certain elements on separate blueprint sheets for convenience;
  6. – A blueprint must be composed with close consideration of the minimum load on relay contacts, position switches etc., using amplifying devices to lower the power these parts commute: electromagnetic, semi-conducting amplifiers etc.;
  7. – Various contacts in one and the same electromagnetic device (such as a contactor, relay, master controller, directional switch and others) are recommended to be connected to one pole or phase in the network if possible. This allows implementing the more reliable performance of hardware (excluding the possibility of failures on top of the isolation between contacts). Thus, a single coil lead from all electric hardware components should be connected to one drive circuit pole;
  8. – In order to establish the reliable performance of electric equipment, the initial blueprint must visualize electric protection and blocking measures. Electricity-powered hardware must be protected from power failures and overloads. The under-voltage protection is necessary for the electric drive control circuits to eliminate the possibility of electric drives’ self-launch when releasing and further providing the power voltage;
  9. – An electric circuit must be constructed in such a way that when preventers burn or contacts are being soldered, the emergency situation wouldn’t take place. Additionally, control circuits must feature blocking connections for preventing emergency modes due to operator errors and to set the defined subsequency of operations;
  10. – For the accessibility of use and correct mounting of the equipment, clamps of all system elements (main contacts, auxiliary contacts, coils, wirings, and others), as well as wires, are marked in circuits. Thus, parts of positive-polarity direct-current voltage chains are marked with odd numbers, and with even numbers for the negative polarity.

Covering Additional Circuitry Elements

As you might have already understood, the linear actuator control system will be different for each separate case, with a certain operation algorithm. There is, however, a general part that every actuator requires. In particular, this goes for the system of indicators that provide the electric motor shutdown in the utter actuator positions (or in the required stop points, as a half of an actuator’s actual range can be used in some cases). I.e., you will need some end switches.

The shut-down feature is realized the following way: the switches are used that come into mechanical contact with the moving part of an actuator or with the part which an actuator sets in motion. Any normally-opened contacts can serve as such terminal switches. When they work out (in the case of power failure, for example), the transistor base is short-circuited to the ground, the transistor locks down, and the relay is deactivated.

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Most probably, you will also have to install a capacitor which will eliminate the contact chatter.

Linear Actuators: Where to Buy Them?

Interested in purchasing high-quality linear actuators at reasonable prices? Come take a look at our online store. There, you will find the widest range of actuator models, including some readymade solutions based on linear actuators (e.g., TV lifts and table lifts).

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