Optoisolated transistor drivers microcontroller interfacing. The 3pin header on the left selects how your program turns on the relay. Optocouplers ssrs consist of an optical transmitter, typically an infrared light emitting diode irled, and an optical receiver, for example a phototransistor mosfet triac, which are both separated in a housing through a transparent insulating material. This is a 5v 4channel relay interface module, for controlling various appliances, and other equipments with large current. Relay drivers gate drivers are available at mouser electronics. An optocoupler or an optoelectronic coupler is basically an interface between two circuits which operate at usually different voltage levels. The capacitor and resistor in series acts as the transient voltage suppressor to suppress voltage spikes. R2 would be replaced by the input led side of the opto coupler and its current limiting resistor. Driving relay directly from optocoupler, what is best. Figure 21 shows the equivalent circuit of the ps9552, an 8pin dip digital, highspeed optocoupler that incorporates a gaalas infrared emitting diode ired on the input side and a singlechip ic on the output side. The ac relay driver circuit we will build is shown below. Controllers often get an impulse or even been fired by the relay. The hcpl7800 isolation amplifier uses broadcoms optocoupler technology. Refer to the optocoupler section of the isolation and control components designers cata.
The optocoupler circuit we will build with a 4n35 chip is shown below. An opto coupler is a device which encapsules an led and a phototransistor inside a hermetically sealed, water proof, light proof package in the form of an 8 pin ic resembling a 555 ic. The circuit was designed to interface a mains driven thryristor motor controller to low voltage analogue circuitry. Acdc power logic rx hcpl3700 gnd 1 gnd 2 parameter symbol value units storage temperatu. You need a solidstate relay, which has an optocoupler builtin. The relay does work, it has a red power indicator led and a green relay on indicator led. How to connect a relay through an optocoupler homemade circuit. R2 would be replaced by the input led side of the optocoupler and its current limiting resistor. If we use a relay with a rated voltage of 110vac, we must feed it 110v from an ac power source. The circuit is designed to be compatible with most microcontrollers including avr8051picarm and boards such as arduino. Opto coupler vs solid state relay for low voltage application. It is powered from any standard usb bus and has an exceptionally low maximum current consumption of approx. Optocouplers and opto isolators can be used on their own, or to switch a range of other larger electronic devices such as transistors and triacs providing the required electrical isolation between a lower voltage control signal, for example one from an arduino or microcontroller, and a much higher voltage or mains current output signal.
Optocouplers also provides interface between different voltage levels. We, again, feed the ac relay the ac voltage it is rated for. This is the linear opto isolator circuits that use a few parts and cheap. Or, you could control a suitable power device with an opto coupler. With r1 and r2 at those values, the opto transistor will always be switched on. Relay and optocoupler electronics forum circuits, projects and. With optoisolators we can sever this connection including the use of highervoltage power supplies totally isolated from the lowvoltage digital circuits. The problem is that when i am trying to switch a relay according to the attached circuit, relay doesnt toggle. Hcpl 7800a500e a7800 a7800a hcpl7800a high speed optocoupler. So, if the gain of the relay driver is 200 and, the gain of the transistor within the optocoupler is 10, the total gain is now 2,000. With an optocoupler, the only contact between the input and the output is a beam of light. So, if the gain of the relay driver is 200 and, the gain of the transistor within the opto coupler is 10, the total gain is now 2,000.
One advantage over the relay is that it may be turned off via a normally open contact. Circuitlab provides online, inbrowser tools for schematic capture and circuit simulation. Read the edn product teardown showing rockwells use of optocouplers as an isolation mechanism in its micro850 plc and watch the related broadcom interview. You can calculate a limiting resistorsr from the input voltage and current. With opto isolators we can sever this connection including the use of highervoltage power supplies totally isolated from the lowvoltage digital circuits. Typical isolating optocoupler applications include lowvoltage to highvoltage or vice versa signal coupling, interfacing of a computers output signals to external. Relay driver circuit using ic uln2003 with applications. You mean like its alternative, or like the next in series device. Technical data pushbutton limit switch sensor optocoupler relay or optocoupler plc motor contactor motor. It is difficult to use a number of relays with transistors, so, relay driver ic uln2003a can be used for availing more relays.
It consists of an aluminum gallium arsenide algaas light emitting diode led optically coupled to a cmos detector with pmos and nmos output power transistors integrated circuit power stage. Latchingnonlatching relay driver circuit with darlington optocoupler. The simple application circuit of figure 2 can be used with digital inputoutput signals only but, in practice, this basic circuit can easily be modified for use with analog inputoutput signals, as shown later in this article. Firstly, the input voltage will be changed into a current. The circuit shown in figure 1 will drive the relay through optocoupler in same circuit with same power supply. For example, separate the circuit from the power line, send an audio signal. As we know, a diode is required to protect the circuit from the reverse current inducted from the coil when power off the relay. This means that you require much less forward led current from the controller io port pin to turn on the relay. How to make an 8 channel relay driver board optically isolated. Elegoo 8 channel dc 5v relay module with optocoupler.
How to connect a relay through an optocoupler homemade. In general, while designing electronics projects the loads are controlled switched on or off using microcontroller block. Circuit b opto coupler upsets circuit a opto couplers. How to build a relay driver circuit learning about electronics. Use them in any sector of industry including process technology and power engineering, railway applications and. The useful purpose of isolation is to provide protection from high voltage, surge voltage and low level noises that could be produces errors in the output.
How to build an optocoupler circuit learning about electronics. An optocoupler a solid state relay ssr is an electronic device which is used to transmit a signal between two isolated circuits. And, the input current at output of a normal digital circuit is about 2 ma. The key advantage of an optocoupler is the electrical isolation between the input and output circuits. Operating supply voltage vcc operating supply voltage v 4 6 8 10 12 14 16 18 20 i c c l. These din rail mount opto couplers from phoenix contact provide an ideal means of interfacing onoff signals to, or from, equipment, whilst providing electrical isolation between their own inputs and outputs. Now i am trying to use optocoupler pc817 as a switch in place of transistor. Logic output optocouplers gate drive coupler 10v 1a enlarge mfr. But, for this purpose the circuit requires relays, acting as controlled switches for different circuits different types of relays are used. This interfacing is possible thanks to abbs relays and optocouplers ranges, which offer wide adaptation in both voltage from 5 to 400 v and current from 107 to 16 a as well as high isolation between input and output from 2 to 4 kv. Typical relay current driver circuit use an optocoupler connected to a transistor which then drives the relay. It can be controlled directly by microcontroller raspberry pi, arduino, 8051, avr, pic, dsp, arm, arm, msp430 ttl logic. A toggle switch was placed on the input side of the optocoupler circuit in order to switch on and off the circuit.
An3007 using nec optocouplers as gate drivers in igbt and. We have to make sure that base gets enough current to turn on the transistor. Before studying the proposed design, lets first understand how an opto coupler works. It also means that you need to have sufficient current available in your micro controller to energize the relay coil. The usb opto rly88 provides eight optically isolated inputs and eight volt free contact relay outputs with a current rating of up to 1amp each. How to build an optocoupler circuit hacked by 4lf45t. An optocoupler wont be able to switch a load like the relay. The relay coil can only be powered from the vcc pin so the optocoupler is not necessary and has no benefit to the circuit. These tools allow students, hobbyists, and professional engineers to design and analyze analog and digital systems before ever building a prototype. In other words, these may be used to protect equipment by electrically.
But the circuit shown in figure 2 is completely isolated from. You would also need a suppression diode across the relay coil to protect the transistor. The phototransistor can be used to switch current in the output circuit. Few realize how close an optical coupler resembles a relay.
Phoenix contact opto couplers with solid state relay output. You have not indicated what is the relay coil currentresistance. In the circuit below is most transistor relay driver circuit. Analog opto isolator this is a circuit to use a standard, low quality opto isolator to transfer an analogue signal with reasonable linearity and without complicated feedback loops to monitor and linearise it. On semiconductors fod3182 is a 3 a output current, highspeed mosfet gatedrive optocoupler. About 44% of these are integrated circuits, 7% are other electronic components. An optocoupler is a device which encapsules an led and a phototransistor inside a hermetically sealed, water proof, light proof package. Igbt and mosfet driver, optocouplersisolators manufactured by vishay, a global leader for semiconductors and passive electronic components. I was planning to use a 3904 npn transistor with a 330 ohm resistor on the base of the 3904. Or, you could control a suitable power device with an optocoupler. Also place a current limit resistor in series with the arduino output, to limit current to the opto led. These simple optocoupler relay driver circuits can be used in variety of electronic projects. In this project, we will show how to connect an optocoupler chip to a circuit.
This above circuit built on a breadboard is shown below. Being that the optocoupler cannot work unless the ir led is on, we can switch on and off the circuit by. I want to use raspberry pi gpio pins to control a few relays. The normally open, normally closed and common pins are all. I would say the connections on the relay side to the opto are back to front. What is the difference between a relay and an optocoupler.
It is so close, in fact, that one can be wired as a runstop latch circuit. So, all you need is a normal transistordriven mosfet circuit, and a normal microcontrollerdriven led circuit. Each relay has normally open and normally closed contact. Types of relays and relay driver circuit buchholz relay. The input to the opto is okay, but the output is wrong way round. Linear opto isolator circuit electronic projects circuits. Can omit resistor for about 15 ma into diode vcc 17459 note. Your external 12 volt supply connects to the voc pin on the 4pin header.
The input current of an opto coupler can be phototransistor, ldr. We can use seven relays with relay driver circuit using uln2003 and the relay driver circuit using uln2803 enables to use eight relays. Your optocoupler will have a current transfer ratio of 400% at 3ma led current, this makes 12ma running thru q1. In part 1 we looked at a number of bipolar transistor and mosfet driver circuits. I am dealing first time with optocouplers so kindly tell my mistakes. Circuit b optocoupler upsets circuit a optocouplers. If the transistor gets enough base current then the transistor conducts and relay energizes. Usboptorly88, 8 optically isolated inputs, 8 relay outputs. For the love of physics walter lewin may 16, 2011 duration. In this environment circuit designers use galvanic isolation optocouplers to insulate high voltages and isolate unwanted signals. For q2 you need a transistor with hfe greater than 250ma12ma20 mps2222 seems to have hfe of 75 at base 10ma current, so you should be ok. Use them in any sector of industry including process technology and power engineering, railway applications and machine engineering, as well as general control cabinet construction. Although on measuring voltage with multimeter, it shows 12 v, but doesnt toggle it.
You need a solidstate relay, which has an opto coupler builtin. The 3pin header on the left selects how your program. In circuit we use the opto compiler ics number of moc 5010 as a base. These relays are also called as impulse relay, stay relays or keep relays as they continue the process what they are doing in the last state. Relay module 1 no high level 6 mm spacing relay mod. Optocouplers and optoisolators can be used on their own, or to switch a range of other larger electronic devices such as transistors and triacs providing the required electrical isolation between a lower voltage control signal, for example one from an arduino or microcontroller, and a much higher voltage or mains current output signal. Optocoupler tutorial about how optocouplers and optoisolators use light to. Here is the list of various types of relays, their working and applications. In this application you could isolate the thyristor controller with a. The below shows the control logic circuit used in the optocoupled relay board. The moc3041, moc3042 and moc3043 devices consist of gallium arsenide infrared emitting diodes optically coupled to a monolithic silicon detector performing the function of a zero voltage crossing bilateral triac driver.
The in1 and in2 pins connect to your arduino, just as i wrote before. The most distinct part of optocoupler as a switch is to isolate low voltage circuit from high voltage circuit. Relay contact monitor current sensing microprocessor interface industrial controls a 0. The hcpl7800 isolation amplifier family was designed to sense current in electronic motor drives. Opto coupler are designed to provide complete electrical isolation between an input and output circuits. Online schematic capture lets hobbyists easily share and discuss their designs, while online circuit simulation allows for quick design iteration and. The working of moc 5010, it will change current that move at input into the voltage as ratio of the input current. Basically, the gain of the one transistor is multiplied by the gain of the second transistor. Isolated outputs with an isolation voltage range of to 5000v can be provided simply by adding additional optical couplers. They had a flaw of having to be electrically connected to low voltage digital circuits. For demonstrating the working of this relay module, we have used. As shown in the following circuit diagram, the relay driver may consist a npn transistor or a pnp transistor. The usboptorly88 provides eight optically isolated inputs and eight volt free contact relay outputs with a current rating of up to 1amp each.
Some time this method is not enough for a poorly configured power supply, as most diy modules have. In this 4channel relay driver circuit we have used an optocoupler whic his triggered by active low signal, to trigger the npn transistor which further drives the relay. An optocoupler or optoisolator chip is a chip that allows for electrical isolation between the input of the circuit and the output of the circuit. The circuit as drawn will not work, i would also advise you, use a transistor driver after the opto. When there is no base voltage, the transistor is in open thus blocking the current through coil of the relay. The wellestablished relaydriving circuit uses an optocoupler to isolate the grounds and noise coupling between the lowvoltage digitalcontrol signal circuit.
Public circuits, schematics, and circuit simulations on circuitlab tagged optocoupler. Igbt and mosfet driver optocouplersisolators vishay. Place your dmm on the relay coil terminals and read the voltage there when you try to turn it on. Logic output optocouplers ipm driver 10mb enlarge mfr. Here we have used 12v 10amp relay in this pcb board, but you can also use 5v relays. Heres an example of driving a mosfet with a transistor. Examplein terms of usage say a person wants to turn on 500 kw motor, he could simply. Electrical engineering stack exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. The most important reason is the coil in the relay is a pretty complex load in the circuit.
1236 393 1499 1569 268 350 270 1041 1035 565 1145 1327 182 1537 1504 1675 1384 1398 281 1189 1311 969 753 1186 692 389 719 449 397 1579 209 1043 392 296 162 1168 38 1224 34