Diy arduino relay driver shield pcb circuit digest. The main control mechanism would be a npn transistor which would get its base from an optocoupler, since i want the arduino be isolated from the 9v circuit. Few realize how close an optical coupler resembles a relay. As shown in the following circuit diagram, the relay driver may consist a npn transistor or a pnp transistor. Jul 17, 2016 relay status indicator light indicates the relay onoff. One advantage over the relay is that it may be turned off via a normally open contact. The key advantage of an optocoupler is the electrical isolation between the input and output circuits.
Jan 17, 2020 the following post describes how to drive a relay by using an isolated method, or through an opto coupler device. 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. But remember to keep the mcu ground and relay ground separate if you use optocouplers otherwise it defeats the purpose of the isolation.
Opto coupler are designed to provide complete electrical isolation between an input and output circuits. 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. In part 1 we looked at a number of bipolar transistor and mosfet driver circuits. The circuit allowed the output of a relay driver to connect to a computer even though the relay driver delivered a voltage as high as 24v and the relay driver had no ground connection. An optocoupler or an optoelectronic coupler is basically an interface between two circuits which operate at usually different voltage levels. I thought id seen one somewhere in cl but i couldnt find it so heres one i made earlier.
You have not indicated what is the relay coil currentresistance. Here is the list of various types of relays, their working and applications. Opto modules and solid state relays product information 2. Then you would connect an arduino output pin to the cathode of the drive led, with vcc to a current limit resistor to that anode. Microopto solid state relays datasheet 376 kb download. Circuit b optocoupler upsets circuit a optocouplers. Optocouplers photocouplers are available at mouser electronics.
Design note optocoupler feedback drive techniques using the uc 3901 and uc3903 numerous techniques and devices are available to the designers of optocoupler feedback circuits. There is still a driver transistor present, so it is not component saving. Igbt and mosfet driver, optocouplersisolators manufactured by vishay, a global leader for semiconductors and passive electronic components. You mean like its alternative, or like the next in series device. Nov 16, 2014 in part 1 we looked at a number of bipolar transistor and mosfet driver circuits. The circuit as drawn will not work, i would also advise you, use a transistor driver after the opto. Optocouplers have existed in various forms since the late 1960s and find use in many different applications. With an optocoupler, the only contact between the input and the output is a beam of light. The transistor is typically and solely employed for operating the relay in response to the commands received from the preceding control stage. The driver circuit needs some form of current limiting resistor to avoid damaging the opto coupler diode.
Here we have used a 12v 10amp relay in this pcb board, you can also use 5v relays. It can be controlled directly by microcontroller raspberry pi, arduino, 8051, avr, pic, dsp, arm, arm, msp430 ttl logic. Electrical isolation between input and output circuits. Typical isolating optocoupler applications include lowvoltage to highvoltage or vice versa signal coupling.
Jul 07, 2015 circuit b opto coupler upsets circuit a opto couplers. For demonstrating the working of this relay module, we have used. 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. 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. Here we have used 12v 10amp relay in this pcb board, but you can also use 5v relays. Driving relay directly from optocoupler, what is best. 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. The below shows the control logic circuit used in the optocoupled relay board. This means that you require much less forward led current from the controller io port pin to turn on the relay. 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 when the power is switched off. As well as the standard common emitter configuration for a relay switch circuit, the relay coil can also be connected to the emitter terminal of the transistor to form an emitter follower circuit.
How to connect a relay through an optocoupler homemade. Electrical engineering stack exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. The wellestablished relay driving circuit uses an optocoupler to isolate the grounds and noise coupling between the lowvoltage digitalcontrol signal circuit left and the relay as load right. Circuit analysis with leds, bjts, relays, opto couplers. 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. May 23, 2012 a very simple model of a typical optocoupler. Whether relay sockets or pluggable relay and optocoupler modules, wagos array of relays and optocouplers offer a solution for any requirement. In circuit we use the opto compiler ics number of moc 5010 as a base.
Here is a simple microcontrollerrelay interface circuit with perfect galvanic. Each relay has normally open and normally closed contact. For the isolation i have used a 4n33 opto isolator. These simple optocoupler relay driver circuits can be used in variety of electronic projects. 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. A relay driver is nothing but an additional transistor stage attached with the relay which needs to be operated. Before studying the proposed design, lets first understand how an opto coupler works. The capacitor and resistor in series acts as the transient voltage suppressor to suppress voltage spikes. I need to know for what i c current of the optocoupler i need to design the circuit. This is the linear opto isolator circuits that use a few parts and cheap.
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. You need a solidstate relay, which has an optocoupler builtin. I need help with my circuit optocoupler, transistor, relay need help hooking up an h11aa1 optocoupler to detect current in an ac circuit. The use again of optoisolation with the use of series speed control circuits placed in either the ground side of an hbridge or in vcc. Relay and optocoupler electronics forum circuits, projects. If you want complete isolation, you will have seperate 5v supplies, one for the arduino and one for the relay power. The most distinct part of optocoupler as a switch is to isolate low voltage circuit from high voltage circuit. Apr 18, 2017 well, the answer is very simple both are switches.
The more traditional approaches utilize either an adjustable shunt regulator like the tl431 device or an opamp and voltage reference as the optocoupler driver. 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. Linear opto isolator circuit electronic projects circuits. A lot of these seem to use an optocoupler, driver transistor and a relay to drive the load example on amazon why are they implemented like this. With power indicator,8way road has a status indicator. Or, you could control a suitable power device with an opto coupler. Oct 30, 2008 with r1 and r2 at those values, the opto transistor will always be switched on. My problem with this setup is that my transistor is not working and im not exactly sure why.
Just to specify the way this circuit is not working. Public circuits, schematics, and circuit simulations on circuitlab tagged optocoupler. Basically, the gain of the one transistor is multiplied by the gain of the second transistor. Microseries class 1, division 2 approved relays 244 kb download. Referring to the above circuit diagram we see that the configuration only. Calculate the value of the led current and the value of current through the 3 k resistance. Microcontroller relay driver and interface electroschematics. We, again, feed the ac relay the ac voltage it is rated for.
How to build an optocoupler circuit learning about electronics. And optocoupler will be triggered by the active low signal. Sep 15, 2019 this is the linear opto isolator circuits that use a few parts and cheap. It is so close, in fact, that one can be wired as a runstop latch circuit. Distinguishing between optocoupler and solidstate relay.
When this input output 1 relay or optocoupler becomes disabled. The driver circuit needs some form of current limiting resistor to avoid damaging the optocoupler diode. On semiconductors fod3182 is a 3 a output current, highspeed mosfet gatedrive optocoupler. The use again of opto isolation with the use of series speed control circuits placed in either the ground side of an hbridge or in vcc. Because optocouplers suffer from a myriad of technical issues, the user community has been forced to remedy optocoupler quirks by adding external components.
How to build an optocoupler circuit hacked by 4lf45t. This video used the ground side while the page on the ta8050p hbridge control used the vcc side. If you want to use ac you can use a triac instead of a relay and a triacoutput optocoupler, but then the load has to be ac too, otherwise the triac will stay on. Digital isolator evolution drives optocoupler replacement. Most opto coupler diodes have about 1v drop when conducting 30ma current.
Technical data pushbutton limit switch sensor optocoupler relay or optocoupler plc motor contactor motor. What is the difference between a relay and an optocoupler. Relays provide as good or better isolation than most optocouplers. 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. Optoisolated transistor drivers microcontroller interfacing. The diagram of figure 2 shows a bidirectional opto coupler input interface circuit. I figured that the logic gets inverted when i used the gpio as the source voltage for the opto isolator led.
When a supply voltage of 20 v is applied the led carries a current and 2 v is dropped across it. Types of relays and relay driver circuit buchholz relay. Circuit options explore issues, solutions for relay drivers. For example, separate the circuit from the power line, send an audio signal, electronic medical, etc. With optoisolators we can sever this connection including the use of highervoltage power supplies totally isolated from the lowvoltage digital circuits. Using an optocoupler to control a basic led driver circuit. An optocoupler is a device which encapsules an led and a phototransistor inside a hermetically sealed, water proof, light proof package. 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 isolators optocoupler with ac input vishay. This is a 5v 4channel relay interface module, for controlling various appliances, and other equipments with large current. Volt drop across inverter is activating optocoupler circuit. The diagram of figure 2 shows a bidirectional optocoupler input interface circuit.
Mar 23, 2015 few realize how close an optical coupler resembles a relay. They had a flaw of having to be electrically connected to low voltage digital circuits. 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. I am controlling a relay with stm32 micro controller. The input signal is connected directly to the base, while the output is taken from the emitter load as shown. When driving from 12v, the current limit resistor needs to be. Or, you could control a suitable power device with an optocoupler. Oct 05, 2008 i need help with my circuit optocoupler, transistor, relay need help hooking up an h11aa1 optocoupler to detect current in an ac circuit.
The circuit shown in figure 1 will drive the relay through optocoupler in same circuit with same power supply. Typical relay current driver circuit use an optocoupler connected to a transistor which then drives the relay. Optocoupler with ac input, optocouplersisolators manufactured by vishay, a global leader for semiconductors and passive electronic components. Igbt and mosfet driver optocouplersisolators vishay. The wellestablished relaydriving circuit uses an optocoupler to isolate the grounds and noise coupling between the lowvoltage digitalcontrol signal circuit. Transistor relay driver circuit with formula and calculations.
An optocoupler wont be able to switch a load like the relay. Jun 24, 2010 an opto coupler wont be able to switch a load like the relay. Relay drivers gate drivers are available at mouser electronics. The circuit is designed to be compatible with most microcontrollers including avr8051picarm and boards such as arduino. Relay module 1 no high level 6 mm spacing relay mod. 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. I want to use raspberry pi gpio pins to control a few relays. With r1 and r2 at those values, the opto transistor will always be switched on. Most optocoupler diodes have about 1v drop when conducting 30ma current. Examplein terms of usage say a person wants to turn on 500 kw motor, he could simply. Isolated outputs with an isolation voltage range of to 5000v can be provided simply by adding additional optical couplers.
I was planning to use a 3904 npn transistor with a 330 ohm resistor on the base of the 3904. You need a solidstate relay, which has an opto coupler builtin. Im designing an optocoupler circuit whose output will be give to one of the arduino input pins. The ac relay driver circuit we will build is shown below. As my relay coil needs around 250 ma, i used a mps222 transistor.
Elegoo 8 channel dc 5v relay module with optocoupler. In this project, we will show how to connect an optocoupler chip to a circuit. If we use a relay with a rated voltage of 110vac, we must feed it 110v from an ac power source. The following post describes how to drive a relay by using an isolated method, or through an optocoupler device. The question was asked by one of the interested members of this blog, miss vineetha.