Frequently Asked Questions

About Relay

What is a relay?

Relay is an electronic control device with a control system (that is, an input loop) and a controlled system (output loop), and are usually used in automated control circuits. The relay is actually an "automatic switch" that uses a small current to control the operation of a large current. It plays the role of conversion circuit, automatic adjustment and safety protection in the circuit.

What are the requirements for the input ends of solid state relay? provides two types of solid state relays, DC and AC input control. DC control input all use constant current source circuit, with input voltage range of 3-32V DC, convenient to connect with TTL circuit and microcomputer interface. The positive and negative polarity of control terminals should be paid attention to under installation. AC control input of solid state relay is also available with control voltage ranging from 70 to 280V AC.

How to select a solid state relay based on load types?

There is no problem for SSR to switch on/off the normal loads, but some special load conditions should also be considered so as to avoid the unnecessary damages to the device caused by excessive impact current and overvoltage. In the use, the steady-state current flowing through SSR output should not exceed the rated output current under relevant temperature as stipulated in the product specifications. The possible inrush current cannot exceed the overload capacity of the relay. Generally, there should be some margin.
The rated current of SSR is selected according to different load types.The instantaneous current of resistive load, inductive load and capacitive load is large when starting. Even for the load with pure resistance, the resistance value is small in cold state because of the positive temperature coefficient, so it has a large starting current. For example, the starting current of asynchronous motor is 5 to 7 times as large as rated value, and the starting current of DC motor is larger. Moreover, the inductive load has higher back EMF. This is an indeterminate value, varying with L and DI/DT, usually 1 to 2 times higher than the power supply voltage, which is superimposed with the power supply voltage. Thus there exists a voltage 3 times higher than the power supply voltage. Capacitive load has potential risk. When starting, the capacitor (load) is equivalent to a short circuit because the voltage at both ends of the capacitor cannot be mutated.
Therefore, when selecting solid state relays, users should carefully know about the surge characteristic of load, and then make a decision. SSR can bear the surge current in the case of ensuring its stable working. Generally, the ordinary SSRs can be selected based on the 2/3 of its rated current value. The enhanced SSRs may be selected according to the parameters provided by the manufacturer. In the harsh conditions such as industrial control sites, it is recommended to leave enough voltage and current margin.

What is a timer relay?

A timer relay refers to a relay whose output circuit needs a specified time to produce a jumping change (or contact action) after adding or removing the input action signal. It is an electrical component used on a circuit with a lower voltage or a smaller current to switch on or off a circuit with a higher voltage and a larger current.
ATO timer relay is a very important component in the electrical control system. In many control systems, timer relays are required to implement timer delay control. It is an automatic control electrical appliance that uses the principle of electromagnetic or mechanical action to delay the closing or breaking of contacts. Its characteristic is that there is a delay from the time when the attracting coil gets the signal to the action of the contact, which is generally used for the motor starting process control with time as a function.

How to adjust the time of timer relay?

1. Adjust the static core and armature between the non-conductive shims
Non-conductive shims of different thickness change the working air gap, air gap changes, the armature closed after the stable flux also changed, because the flux in normal operation is close to saturation, air gap change is not much on the size of the stable flux almost no effect, but access to a certain thickness of the shim will make a significant change in the residual flux, thus changing the position of the flux change curve, in the release of the spring tightness of a certain situation, the release flux Therefore, increasing the thickness of the shim can reduce the delay time; conversely, it will increase the delay time. Non-conductive shims are generally made of phosphor bronze sheet, thickness of 0.1, 0.2, 0.3mm, this method of adjusting the delay is a step adjustment, so it is used for coarse adjustment.
2. Adjust the release spring
The tighter the release spring, the greater the reaction force, the easier to open the armature, the smaller the delay, and vice versa, the looser the release spring, the greater the delay, the release spring adjustment has a certain limit, can not be unlimited loose release spring to achieve increased delay, because the spring is too loose, the delay will be inaccurate, and even the armature will not be released; the same can not make the spring too tight, so as to avoid the armature can not be absorbed, this method can be continuously smooth adjustment, so for fine tuning.

AC relay vs. DC relay: what are the differences?

DC relay
The DC relay consists of a coil, an iron core and several groups of normally open and normally closed contacts. When the relay coil is connected to the DC power of the rated voltage, the coil generates a magnetic field, attracting the iron core to act, the normally open contact connected to the iron core is closed, and at the same time, the normally closed contact is disconnected. When the relay coil is de-energized, the coil loses the magnetic field, the attracted iron core returns to its original position under the action of the spring, the normally open contact connected to the iron core is disconnected, and at the same time, the normally closed contact is closed. The relay is to control the on/off of the coil to realize the on and off of the contact, so as to achieve the logical control of the equipment.
AC relay
The working principle of the AC relay is basically the same as that of the DC electromagnetic relay. The AC relay works in the AC circuit. When the AC current passes through the coil, an alternating magnetic flux is generated in the iron core. Since the traction force (electromagnetic attraction) is the square of the magnetic flux φ is proportional, so when the current changes direction, the traction force does not change direction, always attracting the armature to the core in one direction.
The coil of the AC relay is short, and the wire diameter is relatively thick, mainly because the reactance of the coil is relatively large after the alternating current is applied, and the thick wire diameter can reduce the internal resistance and heat generation. When the magnetic field changes, an eddy current is formed when the short-circuit ring is formed, and an electromagnetic force opposite to the direction of the magnetic field change is formed, which lags the change of the magnetic field. , so that the electromagnet can be better attracted.

Product Sample

Can I get samples of any relay products at

Certainly. We offer samples, and various relay products can be shipped worldwide. Our product management team is constantly adding new products, and we'll continue to expand the featured offerings on

How to get product samples?

Contact us via email:, tell us what specification you need and the address. Next we will deliver product(s) to you.

How many product samples can I request?

Based on the characteristics of the product, each eligible product has a maximum quantity that can be ordered free of charge. All accounts will be monitored for abuse of the sample program.

Which countries/regions can ATO ship samples to?

ATO can ship ordered samples to 62 countries/regions worldwide.

Who should I contact to discuss issues or get support?

Our customer service representatives are happy to help you place your order and help with any questions or answer any questions, including technical support for the product, inquiry, acquisition of free samples. You can contact our support team by email or phone.

What are the sample order terms and conditions?

ATO reserves the right to refuse sample orders at any time for any reason, including (but not limited to) export control regulations; concerns about abuse; excessive and/or multiple requests; multiple registrations by the same user; and /or prohibited duties/taxes/imposed import restrictions imposed by certain countries.

How can I make an enquiry?

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