Can directly promote the work of the CMOS integrated block circuit relay
Circuit in the electronic enthusiasts know the habits of knowledge, and believe that CMOS integrated block itself can not directly drive relays, but in fact, part of the CMOS integrated block not only can directly drive relays work, and work is very stable and reliable. The relay used in the experiment model JRC5M-DC12V sealed miniature relays (the coil resistance 750Ω). Manifold now CD4066 CMOS drive relay works as follows:

Can directly promote the work of the CMOS integrated block circuit relay
Circuit in the electronic enthusiasts know the habits of knowledge, and believe that CMOS integrated block itself can not directly drive relays, but in fact, part of the CMOS integrated block not only can directly drive relays work, and work is very stable and reliable. The relay used in the experiment model JRC5M-DC12V sealed miniature relays (the coil resistance 750Ω). Manifold now CD4066 CMOS drive relay works as follows:

CD4066 is a four-way analog switch, Manifold SCR1 ~ SCR4 for the control side, used to control four-way analog switch-off. When SCR1 connected high, Manifold ①, ② foot turn, +12 V → K1 → Manifold ①, ② → negative power pin to pull K1; the other hand when SCR1 input low, the integrated block ①, ② legs open, K1 loss of power release, SCR2 ~ SCR4 input high or low status and SCR1 the same.
This circuit, the relay coil in parallel with both ends of a reverse diode, which is used to protect the integrated circuit itself, do not save, or pull in the relay by the state to release, because the inductor the role of the coil will result in higher back-EMF, very easily lead to manifold breakdown. Parallel the diode after the release of the relay from the pull into the moment, the coil will form a short-wheeling diode circuit, the coil current will not be mutated, thus preventing the generation of back EMF in the coil to ensure the integration block safety.
Low voltage relay pull measures
Often because the power supply voltage lower than the relay pull-in voltage and it does not work, in fact, once the pull-in relay can be about half of the rated voltage to work reliably. Therefore, you can start a startup voltage to the relay to pull, and then let it at a lower supply voltage, as shown in the circuit can achieve this goal.
How it works:

As shown. V1 is a single junction transistors BT33C, it R1, R2, R3 and C1 form a relaxation oscillator, SCR SCR for the one-way, press the start button AN1, the circuit is energized, because no SCR trigger voltage, so I do not lead Tong, J does not operate the relay, power VD1 through R4 and capacitor C2 to charge rapidly to nearly the supply voltage (Vcc-VD1 drop.) Meanwhile, the power supply capacitor C1 to charge through R1. After a few seconds, C1 on the trigger voltage charge to voltage V1, C1 now discharges through the V1, in the R3 form a positive pulse, the pulse all the way added to the V2 base so quickly saturated conduction V2, V2 collector capacitor C2 that is cathode near ground. Since this time there is the charge on C2 is positive under the negative polarity voltage, so negative, ie C2 negative potential of J end of the coil. R3 is on the pulse of another path VD2, C3 to trigger the SCR conduction, SCR cathode that is close to J the other end of the coil voltage. At this time, J coil actually take about twice the supply voltage, so the J1-1 is closed, after the release AN1, J1-1 self-preservation. J1-2 to V1, V2 power supply cut off, the relay near the power supply voltages. The figure, AN2 for the stop button, press the AN2, J lost power release, J1-1 break, the entire control circuit is energized.
Making this circuit, is generally preferable to relay rated at 1.5 times the supply voltage, under normal circumstances, any type of one-way thyristor (or triac), can meet the circuit requirements. V2, C1, C3 of the pressure as the power supply voltage level selection. C2 is not less than the best power supply voltage twice.
Three additional circuit relay

Relay is an electronic circuit element commonly used in general by the transistors, relays and other components of the composition of the electronic switch driver circuit, often have to add some additional circuitry to change the operating characteristics of the relay or protective effect. Additional relay circuit mainly has the following three forms:

1. Relay series RC circuit:
Circuit in the form shown in Figure 1, this form is mainly used in the relay rated voltage below the supply voltage circuit. When the circuit is closed, the relay coil will produce the phenomenon of the self-inductance emf hinder the increase of current in the coil, thus extending the pull-time series on the RC circuit can be reduced after the pull time. Closed circuit principle is the moment, the voltage across capacitor C mutation can not be regarded as short-circuit, so that the relay coil than the high voltage power supply rated coil voltage is applied, thereby speeding up the coil current increases the speed, so that quickly pull the relay. Capacitance C does not work after the power and stability, resistance R from the limiting effect.
2. Relay parallel RC circuit:
Circuit in the form shown in Figure 2, the circuit is closed, when the current stable RC circuit does not work, disconnect the circuit, the relay coil inductance and the induced electromotive force generated by the RC circuit is discharged, the coil current decay slowed down, extension of the relay armature release time, play time delay effect.
3. Relay parallel diode circuit:
Circuit in the form shown in Figure 3, mainly to protect the transistors and other drive components. When the figure turns the transistor into cutoff by the VT, the current flowing through the relay coil will decrease rapidly, when the self-inductance of the coil will produce a high electromotive force and the supply voltage in the VT's stacked Jiahou Jia c, e between two poles will lead to transistor breakdown, the diodes in parallel, you can force the self-inductance of the coil in the clamp diode forward voltage, the value of silicon tube of about 0.7V, germanium tube of about 0.2V, transistor and other drivers to avoid breakdown components. Parallel diode must pay attention to the diode polarity is not reversed, or easy to damage the transistors and other drive components.
Non-inductive analog relay
Introduction of a non-inductive analog relays, the circuit as shown below.

The figure, 220V power supply through the load RL, R1, D1 ~ D4, ZD1, for the Q4, Q3 turns on to provide positive and negative half-cycle bias; same time, by R3, D5 ~ D8 optocoupler Q1 to provide power. High-level TTL circuit output current signal, the optical coupler is a half weeks in the city electric conduction, so the pressure drop across R5, triggering SCR turns on, the load RL is energized work. As a function of the relay circuit, but does not produce the reverse induction voltage, the load is also to avoid the breakdown of high back pressure may be damaged. C1, R6 pulse absorption components, R3 from the limiting effect.
To avoid the RL as an inductive load, SCR voltage and power generated by optocoupler 90 ° phase, the optocoupler circuit in the power from the SCR anode instead of directly from the mains power supply.
Small improvements relay circuit
Relay normally installed in the electrical equipment inside, their work status is not intuitive, the author will be as shown improvement. Light-emitting diode connected across the coil VD1, when the control voltage is positive, the transistor turns on, the relay pull-J, while LEDs are lit, indicating that the relay coil is coupled with power. LEDs can be installed in a conspicuous place housing.

Proper use of the relay
1, the choice of relay rated voltage
Rated voltage relay is a relay the most important technical parameters. In the use of the relay, you should first consider where the circuit (ie, where the relay coil circuit) voltage, the relay should be equal to the rated working voltage of the circuit where the voltage. Generally where the circuit voltage is 0.86 rated voltage relay. Note that the workpiece where the circuit voltage must not exceed the rated voltage relays, or relay coil easy to burn. In addition, some integrated circuits, such as NE555 circuit can directly drive relays work, and some integrated circuits, such as COMS circuit output current is small, and needs only one transistor amplifier to drive a relay, which should consider the transistor output current should be greater than the relay's rated current.
2, select the contact loads
Contact load capacity of the contact means. Relay contacts in the conversion can withstand a certain voltage and current. Therefore, the use of relays, should consider the voltage at the contacts and the current through the contacts of the relay contacts can not exceed the load capacity. For example, there is a relay contact load 28V (DC) × 10A, the relay contacts that can only work in the DC circuit voltage of 28V, the contact current is 10A, more than 28V, or 10A, will affect the relay normal use, and even burned contacts.
3, the choice of the relay coil power
This refers to using a direct current relay coil (DC) or alternating current (AC). Usually, beginners in electronic production activities are based on electronic circuits, electronic circuits are often used DC power supply, it must be a DC voltage by the relay coil.