If the relay is transistor driven, we recommend using the relay on the collector side.
The voltage impressed on the relay is always full rated coil voltage, and in the OFF time, the voltage is completely zero for avoidance of trouble in use.
If the coil current is suddenly interrupted, a sudden high voltage pulse is developed in the coil. If this voltage exceeds the breakdown voltage of the transistor, the transistor will be degraded, and this will lead to damage. It is absolutely necessary to connect a diode in the circuit as a means of preventing damage from the counter emf. As suitable ratings for this diode, the current should be equivalent to the average rectified current to the coil, and the reverse blocking voltage should be about 3 times the value of the power source voltage. Connection of a diode is an excellent way to prevent voltage surges, but there will be a considerable time delay when the relay is open. If you need to reduce this time delay you can connect between the transistor's collector and emitter a Zener diode that will make the Zener voltage somewhat higher than the supply voltage.
Unlike the characteristic when voltage is impressed slowly on the relay coil, this is the case where it is necessary to impress the rated voltage in a short time and also to drop the voltage in a short time.
(Wave rectifying circuit)
When the input signal does not produce a snap action, ordinarily a Schmitt trigger circuit is used to produce safe snap action.
This circuit is a trap into which it is easy to fall when dealing with high circuit technology. This does not mean that it is immediately connected to the defect, but it is linked to troubles that occur after long periods of use and with many units in operation.
In switching applications where a semiconductor (transistor, UJT, etc.) is connected to the coil, a residual voltage is retained at the relay coil which may cause incomplete restoration and faulty operation. By using DC coils, there may be a danger of incomplete restoration, and a reduction in the contact pressure and the vibration resistance.
This is because the release voltage is 10% or more of the rated voltage, a low value compared to that for AC coil, and also there is a tendency to increase the life by lowering the release voltage.
When the signal from the transistor's collector is taken and used to drive another circuit as shown in the figure on the right, a minute dark current flows to the relay even if the transistor is off. This may cause the problems described above.
For SCR drive, it is necessary to take particular care with regard to gate sensitivity and erroneous operation due to noise.
|There is no problem even with more than 3 times the rated current.
|1KΩ must be connected.
|This is for prevention of ignition error due to a sudden rise in the power source or to noise. (dv/dt countermeasure)
When the relay contacts close simultaneously with an AC single phase power source, because the electrical life of the contacts suffers extreme shortening, care is necessary.
Relays for PC board use have high sensitivity and high speed response characteristics, and because they respond sufficiently to chattering and bouncing, it is necessary to take care in their drive.
When the frequency of use is low, with the delay in response time caused by a condenser, it is possible to absorb the chattering and bouncing.
(However, it is not possible to use only a condenser. A resistor should also be used with the condenser. )
Even though a chatterless characteristic is a feature of relays, this is to the fullest extent a chatterless electrical circuit, much the same as a mercury relay. To meet the requirement for such circuits as the input to a binary counter, there is an electronic chatterless method in which chattering is absolutely not permissible. Even if chattering develops on one side, either the N.O. side contacts or the N.C. side contacts, the flip flop does not reverse, and the counter circuit can be fed pulsed without a miss. (However, bouncing from the N.O. side to N.C. side must be absolutely avoided.)
|1. The A, B, and C lines should be made as short as possible.
2. It is necessary that there be no noise from the coil section induced into the contact section.
When an electronic circuit using a direct drive from a triac, the electronic circuit will not be isolated from the power circuit, and because of this, troubles due to erroneous operation and damage can develop easily. The introduction of a relay drive is the most economical and most effective solution. (Photo coupler and pulse transformer circuits are complicated.)
When a zero cross switching characteristic is necessary, a solid state relay (SSR) should be used.
In general, electronic circuits are extremely vulnerable to such phenomena as power supply ripples and voltage fluctuations.
Although relay power supplies are not as vulnerable as electronic circuits, please keep both ripples and the regulation within the specification.
If power supply voltage fluctuations are large, please connect a stabilized circuit or constant-voltage circuit as shown in Fig. 1.
If the relay power consumption is great, satisfactory results can be achieved by implementing a circuit configuration as shown in Fig. 2.
In the circuit shown in Fig. 1, rush current flows from the lamp or capacitor. The instant the contacts close, the voltage drops and the relay releases or chatters.
In this case it is necessary to raise the transformer's capacity or add a smoothing circuit.
Fig. 2 shows an example of the modified circuit.
Fig. 3 shows a battery-powered version.
The hole diameter and land are made with the hole slightly larger than the lead wire so that the component may be inserted easily. Also, when soldering, the solder will build up in an eyelet condition, increasing the mounting strength. The standard dimensions for the hole diameter and land are shown in the table below.
Standard dimensions for hole and land diameter
|Standard hole diameter
|2.0 to 3.0
|3.5 to 4.5
Because copperclad laminates have a longitudinal and lateral direction,the manner of punching fabrication and layout must be observed with care.
The expansion and shrinkage in the longitudinal direction due to heat is 1/15 to 1/2 that in the lateral,and accordingly,
after the punching fabrication, the distortion in the longitudinal direction will be 1/15 to 1/2 that of the lateral direction.
The mechanical strength in the longitudinal direction is 10 to 15% greater than that in the lateral direction.
Because of this difference between the longitudinal and lateral directions, when products having long configurations are to be fabricated,
the lengthwise direction of the configuration should be made in the longitudinal direction,
and PC boards having a connector section should be made with the connector along the longitudinal side.
By providing a narrow slot in the circular part of the foil pattern, the slot will prevent the hole from being plugged with solder.
This data has been derived from samples of this company's products. Use this data as a reference when designing printed circuit boards.
The allowable current for the conductor was determined from the safety aspect and the effect on the performance of the conductor due to the rise in saturation temperature when current is flowing.
(The narrower the conductor width and the thinner the copper foil, the larger the temperature rise.)
For example, too high a rise in temperature causes degradation of the characteristic and color changes of the laminate.
In general, the allowable current of the conductor is determined so that the rise is temperature is less than 10°C.
It is necessary to design the conductor width from this allowable conductor current.
Fig. 1, Fig. 2, Fig. 3 show the relationship between the current and the conductor width for each rise in temperature for different copper foils. It is also necessary to give consideration to preventing abnormal currents from exceeding the destruction current of the conductor.
Fig. 4 shows the relationship between the conductor width and the destruction current.
Fig. 6 shows the relationship between the spacing between conductors and the destruction voltage. This destruction voltage is not the destruction voltage of the PCB; it is the flash over voltage (insulation breakdown voltage of the space between circuits.) Coating the surface of the conductor with an insulating resin such as a solder resist increases the flash over voltage, but because of the pin holes of the solder resist, it is necessary to consider the conductor destruction voltage without the solder resist. In fact, it is necessary to add an ample safety factor when determining the spacing between conductors. Table 1 shows an example of a design for the spacing between conductors. (Taken from the JIS C5010 standards.) However, when the product is covered by the electrical products control law, UL standards or other safety standards, it is necessary to conform to the regulations.
Example of conductor spacing design
|November 17, 2022
|Applications of Relays in Electronic Circuits
Power Relays(Over 2A), Safty Relays, Signal Relays(2A or less), Microwave Devices, High-capacity DC Cutoff Relays and Interface Terminal.
|May 30, 2022
|December 21, 2022
|Use MOSFETs in output elements. Semiconductor relay for AC and DC load control.
|Power Relays (Over 2A)
|Mechanical relay with greater than 2A nominal switching capacity that is ideal for power supply applications.
|Safety relay ideal for safety circuit construction , with forcibly guided contact structure.
|Solid State Relays
|Semiconductor relay ideal for heater control, etc. SSR (Solid State Relay)
|Signal Relays (2A or less)
|Mechanical relay ideal for signal control, etc., with less than 2A nominal switching capacity.
|Lineup spans from relays to coaxial switches. High-frequency devices that support high bandwidth frequencies.
|Relays for automotive electrics that includes plug-in PCB type.
|High-capacity DC Cutoff Relays
|400 V DC high voltage switching possible. Up to 300 A current capacity type available.
Requests to customers (Automation Control Components & Industrial Device) [Excluding specific product]
Requests to customers (Automation Control Components & Industrial Device) [For specific product]
Requests to customers (FA Sensors & Components [Excluding motors])
Requests to customers (Dedicated to industrial motors)