A relay is an electrically controlled switch. Electromechanical relays use an electromagnet to activate mechanical contacts, solid-state relays use semiconductor switches.

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Appropriate relay for water heater 1500W

I've created a complete hardware platform using a Raspberry Pi as master/controller, an Arduino nano and two RF24l01 transceivers, which should control some household electrical appliances. The ...
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2answers
50 views

5v vs 12v dc pcb mounted relay selection

I'm newbie and just got stuck at design decision whether to go for 5 volt dc relay or 12 volt dc relay in power circuit.Both relays equally mentions power dissipation as 170mW according to their ...
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0answers
32 views

AC relay parallel [on hold]

Is it possible to connect relay in parallel on AC circuit? I will describe better the problem. In my domotic solution I have a wireless/RC circuit to control a wall socket. It has a transformer to ...
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1answer
43 views

Relay circuit not switching as expected

I work on the book "Make - Electronics" doing some experiments. One of these is working with a relay. The simple schematic is this one: The circuit that I build works to 95%..... The left LED is ...
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1answer
47 views

An SPDT switch using TRIACs

I need to design a circuit that implements an SPDT switch using Triacs and Optoisolators. Currently I am implementing this with two pairs of Optoisolated Triacs with one having inverted signal from ...
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1answer
93 views

Which circuit is more Stable?

The circuits in the picture are basically opto-couplers connected to a relay circuit. The input pin of the opto coupler is connected to a MCU and the output of the opto coupler is connected to the ...
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1answer
43 views

Help wiring DC motor

first post here. I'm wiring a DC motor and horn that will go into a small boat I built. I would like to get some help to see if I'm doing this correctly. -DC motor hooked to a 12v battery (Max draw ...
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1answer
95 views

“switching box” with microcontroller and relays [duplicate]

I need to build a switching box, which switch between 4 pairs of the contacts, and give one of the pairs to the output (to read one of the 4 signals). I am going to do that as follows: For each pair ...
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1answer
52 views

should I use relays?

I am using attiny85 to control 4 motors that work all togather at the same time. Will that hurt the attiny85 controller or is it ok. Because I think that the 4 motors will draw high power through the ...
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1answer
83 views

Relay Vs MOSFET or IGBT

Curious on your thoughts for an application and the pros and cons of using a relay or a MOSFET or IGBT. The application involves switching a 96V lead acid battery pack on and off for periods of 5 ...
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1answer
54 views

Problems with Switching a Solenoid Valve with a Relay

I've been trying to switch a solenoid valve using a relay controlled by a signal from a microcontroller. The circuit works fine when connected to a normal load like a light bulb, but some random ...
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4answers
240 views

Symbol or marking on safety relay

I found this relay inside an industrial x-ray machine. What does the rectangular box with a horizontal line through it, in the bottom left of the first picture, mean?
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28 views

Relay sequencing: Inhibit state change of one relay if the other is on

I'm trying to find a way to have one relay lock its state if the other is on. Example, 2 relays total: If relay 1 is on then relay 2 can't change state, either turn on or off. Meaning if relay 2 is ...
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1answer
130 views

Is this schematic good?

Here is schematic for DC motor control. Using this I can drive motor in both directions and also send short pulses to motor, to move it only a little bit in desired direction. Let me explain schematic ...
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3answers
63 views

Looking for time delay relay or relay circuit that can be reset

Need relay control that results in a closed contact (dry) that is held for 1 minute If during that one minute another signal is received (dry or not) the 1 minute countdown resets. The actual ...
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2answers
66 views

What type of connector / terminal end is this?

This wire comes off a automotive multi-pin relay block/connector housing. Requesting help to identify what type/name of connector it is. -Thanks
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83 views

Energizing relay using short pulse signal

I have DPDT relay which I would like to energize using pulse signal (duration of that pulse should be adjustable) and switch. When switch is on, coil of relay is shortly energized by pulse signal and ...
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2answers
54 views

Do latching relays controlled by two different open/close pushbutton exist?

I need to control a latching relay but I don't need to change its state alternatively with one single input. I need to control its state with two separate pushbutton: "open" and "close". Does it ...
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3answers
121 views

Arduino 16x2 LCD weird symbols after relay-switch

I am using my arduino to automatically change water of my aquarium. The program runs fine, the pumps, heaters and valves are controlled by relays. When connected to my laptop, I can see via the serial ...
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2answers
87 views

Using a multimeter to see if ground is connected

I've been diagnosing a problem with a relay on my car. One of the pins in the socket that the relay goes into controls the ground for the throw of the relay. When the car's computer wants the relay ...
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0answers
23 views

Difference between instantaneous, definite time and inverse time over current protection relays

Protection coordination is very important in transmission and distribution power networks. One of the most widely used and important protection relays are over current protection relays. What is the ...
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2answers
157 views

NodeMCU v2, driving a 5v relay

I was under impression that you can drive 5V relay with no problems, but now it seems you need additional components to do that, which makes it no longer simple. The setup I think now is the following:...
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2answers
88 views

How to protect P-MOSFET from excessive gate voltage

I would like to build a DIY solid state relay for my car to enable some circuits (less than 1A current absorption) only when the accessories are powered up (independently from engine on or off). I ...
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2answers
86 views

Solid state relay operation without transistor

I have this solid state relay, it's specify that it can run at 5v/16mA. I just want to make my board as simple as possible, so i've been thinking to remove transistor. Is that safe for GPIO/PORT or ...
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2answers
47 views

Opinion on design changes for Latch circuit

So just to give some background I've designed a circuit to suit the following task. 12V DC Motor moving a carriage up and down a column 2 'End stop' magnets, active-low hall effect sensor attached ...
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2answers
44 views

How to unlatch relay with relay?

I have problems with unlatching relay with relay.. Schematics below: simulate this circuit – Schematic created using CircuitLab The purpose for this is to light on car sidelights when ...
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0answers
28 views

Protection relay coordination

I have a question in regard to following 66kV/11kV substation single line diagram: Long story short, the question is how different the coordination procedure would be if feeder no. 1's impedance is ...
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1answer
64 views

What Type Of Switch Is only on for a second [duplicate]

I am looking for what type of switch is only only for a split second (1 second max) even when held. Basically: Press and hold button-->LED only on for a split second and back off even though I am ...
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3answers
75 views

Electronically, how to control this 5v arduino-style relay board from a PC serial port

I have the following relay board (pictured below), and to activate any of the relays, you simply connect one of the IN1-IN8 pins to ground. Easy. The current going between gnd and INx is negligible, ...
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2answers
27 views

Connecting multiple input devices to 8 channel relay board

I have an 8 channel relay board (here's a link to the actual product (http://smile.amazon.com/dp/B00KT0E1RY/ref=sr_ph?ie=UTF8&qid=1463753455&sr=1&keywords=smakn+8+channel). I understand ...
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1answer
77 views

How to use arduino nano to switch an 230V AC motor on/off?

I want to switch on and off an 230V AC motor with a relay what is controlled by an arduino nano. The on time and off time would be able to set by a 3-position slider switch. So would be 3 different ...
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0answers
28 views

Switch time for Q-series relays

Im working on a project where I have to read the pulses at a relay contact(FC/BC). The problem is the relay can change from FC to BC and vice versa at any point of time. Every 32ms I read the contacts ...
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1answer
111 views

Relay Feedback Problem

I am a computer science student working on a project for my Diploma and I am building a DIY PDU, I thought building something would be a lot funner then programming a website like 90% of the class ...
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2answers
79 views

I am having an issue with relays sticking

I use a DL205 PLC with a Do more CPU. This drives SPDT relays to control 90 degree motor operated valves. The valves are apollo motor actuated, which advertises 0.74amp starting/locked rotor current. ...
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2answers
36 views

Door lock relay needs higher amperage - what relay to use?

I have a door lock that requires 12VDC 750mA to get it to unlock, then it drops to 350mA to keep it open. My door controller has a max load of 500mA, so it won't work connected directly to the door ...
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3answers
51 views

Properties of relays [closed]

i know how a relay works, my question is this. i have a load that needs to be turned off and on remotely. The piece of equipment is 220volts at 30 amps. is there such a thing as being able to use a ...
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2answers
51 views

Doorbell to buzzer with relay and AC to AC transformer

I have the following buzzer and want to use it with a switch by the door. Would the following configuration let this work or are there crucial parts missing? simulate this circuit – ...
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3answers
71 views

interchangeable operation of two electric motors without PLC

I have two motors that drive an air compressor. I have a pressure switch to turn the motors on/off. The sequence I want is: when pressure switch turns ON - motor 1 starts, when pressure switch ...
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2answers
54 views

Interfacing microcontroller with external circuit - detect LED and simulate and detect button press

This is my first question on here. I am good at programming but am a little stuck when it comes to electronics and connecting two circuits together. I would like to interface a spa controller with 3 ...
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2answers
53 views

Low amp/volt relay for microphone switching

Its that time of year when I revisit one of my old projects and try to improve it. Currently I have a small 12v PA system that has a microphone and I've added an 3.5mm auxiliary input to play music ...
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1answer
66 views

Relay control using Ardiuno Mega [closed]

How many relays can I drive using Ardiuno MEGA board without overloading the microcontroller?
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1answer
36 views

capacitance calculations

I am trying to calculate what size capacitor I need to energize a small relay coil for 5 to 8 seconds while the supplied voltage is removed momentarily . My supply voltage is 12 VDC, Relay coil draws ...
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2answers
27 views

Connectors: Relay to Heater

Simple project: Swap the on-off switch on a coffee-maker with a relay. The relay is rated to be safe for wall power. The coffee-pot can take it, obviously. But the old crimp-on connectors that the ...
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1answer
50 views

PIR Sensor University Project

I'm working on a project to use PIR sensor to save on electricity bill in a university, almost a fresh graduate in Electronics Eng. Load is Fluorescent tubes 44w each via ballast,there will be ...
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2answers
42 views

Circuit todelay RS-232 TX pin closure after device power up

We have two devices connected via a cable, an ARM based computer on one side and a sensor on the other. This cable carries an RS232 TX, RX, and ground. In addition there is 28V provided from the ...
39
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6answers
6k views

Why are there so many relays used in a car, instead of transistors?

Recently I did some work on my car electric circuits. I see many relays are used in car circuits. These relays are used for simple switching, and I wonder why these circuits are based on relays and ...
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votes
1answer
50 views

relay coil issue

i've been googling my way through a problem and now i am stuck and haven't found an answer. So here is what I am trying to do. i have 24vdc connected to the positive side of the coil on a relay and ...