Questions tagged [relay]

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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39 views

Driving 3 Relays with ESP01

I would like to drive 3 relays with single ESP01 pin (RX in this case). However, the ESP keeps clicking along with relays sometimes. in other times nothing happens. it doesn't work. I used the same ...
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1answer
42 views

Driving Relay using ESP-01 Module

I am trying to control a 5V relay with a push button with an indicator LED using GPIOs 0, 1 and 3. I have pulled up the GPIO0 and using it as output, so that when I drive it low, the LED should glow, ...
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766 views

Controlling Relay using ESP8266 Module

I have 5 such relays attached to an ESP-12E module with a 600ma Power Supply. The LED (LED4) glows but the relay doesn't switch. Is there anything wrong with my schematic? Using MMBT3904 instead of a ...
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99 views

How to add a flyback diode to protect a relay on another PCB that does not have a flyback diode

I have a PCB (SEPARATE PCB) that I want to test by building up a "Test PCB". The test will involve switching the relays. This PCB (SEPARATE PCB) has a few relays on it, however, they do not ...
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56 views

Minimum load (current) through relay contacts: low current, bad contact?

I use photocells connected to very "consumer" gate automation boards. Those photocells output the infrared beam status via a relay with potential free contacts. The relay is the Hongfa HFD23 ...
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1answer
80 views

Can I send 12 volts to a 6 volt relay?

I currently have a 12 volt LED light strip that I would like to work with my welcome lights on my vehicle. The system outputs 4.5 volts for the welcome lights, then it goes up to 12 volts once the ...
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1answer
94 views

Would this cause a dead short?

I am attempting to install an oil pressure sensor / sender unit for an automotive application. My concern is with adding a relay to make the internally triggered NO switched contact inside the sensor ...
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2answers
106 views

Control a 120 Vac relay with a triac. Good idea?

I'm beginning the design of a light control system based on a microcontroller. This is to activate the lights, what is usually used are continuous voltage relays, in ranges of 5, 12 or up to 24 VDC. ...
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29 views

Relay to drive actuators

wanting to use 240v AC motor controller to drive a DIY TV lift that uses DC actuators. The AC controller has Neutral, L1 and L2 outputs. Will it work if I… Wire 240v AC L1 and L2 outputs to each side ...
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2answers
59 views

Relay selection for 48V loads

I want to use a relay to remotely switch a 48VDC 1A load (3A peak on startup with capacitive load), however, nearly all relays I have looked at specify a 30VDC maximum contact voltage. When searching ...
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50 views

6V-12V to on/off switch conversion

In order to connect/disconnet a battery pack I need to use a timer (https://www.highwildoutdoors.com/products/6v-12v-universal-digital-timer) which seems has 6v-12v output. I am not sure which relay I ...
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1answer
52 views

How does a relay behave when its resistance is increased or decreased? [closed]

I have a relay of coil resistance 200 ohm whose input voltage is 12V DC. Now, under the same 12V DC supply, will the relay be activated when: The relay coil is decreased, say by 100 ohm i.e. new coil ...
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1answer
38 views

Only 1 Pole of DPDT relay switching

I have a NO DPDT relay, non latching, 12V coil controlled by transistor. One pole is switching fine. The other pole is stuck closed until I give it a few taps with a screwdriver. These are new ...
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43 views

Car Head Unit, relay, 12V

Given: a Head Unit that starts with a signal of voltage 12V, Relay Prowest 4120-1C-DC12V (12VDC, 1C, 40A / 14VDC) for switching the cigarette lighter, 12 volts from emergency button light :-), 12 ...
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Powering an Eletechsup nc25c01 water level control [closed]

The Eletechsup nc20c01 manual (google) shows a 12VDC isolated power supply but shows no model or part number. How can I find the part?
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What type of wire can I use to run 5V, 30A to my Arduino controlled relay module over a distance of 10-12m?

I'm building an Arduino-controlled Christmas light show. I power my 16-channel relay module with a 5V, 30A supply. It is placed outside the house and I want to place its power supply powering the ...
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2answers
100 views

How do you replace an NC relay with a Schottky and transistors, or MOSFETs?

I'm a beginner and am trying to build a simple power control circuit. The load of the circuit is the coil of a relay. Nothing else. According to the datasheet it has 70 ohm internal resistance, but I ...
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26 views

Uncertainty regarding EU regulation for switching devices

Our company is working on developing an AC electric car charger for the EU market. One part of the design process is choosing a suitable relay for this application. In the standards it is required ...
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2answers
76 views

Relays connected in series?

I have 2 identical relays (same specifications) whose working input voltage is 12V DC. Can I connect the 2 relays in series by supplying 24V DC so that there will be 12V DC drop across each of the 2 ...
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1answer
60 views

relays 5V 10A and 12V 30V stop working after a few days of use

We built a system for heating 3 bioelectrochemical reactors, but after a certain time of operation the system starts to heat up. We identified that when this occurs, the relay works despite the light ...
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1answer
35 views

Time relay and solenoid valve

For a project, I need to control a normally closed solenoid valve and be able to apply a current on the valve only for a set amount of time before closing it again, and only once (so no cycle). I ...
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23 views

Power switch for 8Pin ATX Connectors

What would be the best way to make a power switch for the 8-pin ATX Power Connectors? Can I just join all the yellow (12V) wires together and then use a high current switch to toggle them ON/OFF? Also ...
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3answers
68 views

Sticky/Intermittent Relay Driven by MCU and NPN Transistor

I have an MCU (1.8 V logic levels) driving an NPN transistor to turn an relay on/off. The relay has a 12 V DC coil with resistance of 1028R per datasheet. This would require a current of 12/1028 = 11....
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63 views

How to spec a inrush current resistor?

I want to know how do I spec a limiting resistor for the below circuit: The relay used is this. The power supply input is 48V and the output is 12V DC. First switch SW1 is pressed which powers the DC/...
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67 views

Can you explain the working of below relay ? It has 4 legs and it was in car

It was in my car and has been replaced. Due to it car horn was not working.
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1answer
50 views

How to derate a relay switiching for a capactive load

How do I derate this graph for the switching contact of this relay? The contact spec is 48V DC at 1.8A. From the graph below the Max DC load for 1.8A is 90V DC, so I do derate this for a capacitive ...
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4answers
71 views

Voltage protection with relay and Zener

I'm having a hard time finding a good way to protect a radio module if the voltage regulator fails and injects the battery's input voltage. The module is expensive, so I would like to protect it from ...
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1answer
74 views

Converting Normally Closed to Normally Open

I have a truck that has a different engine swapped into it. I'm trying to get the cruise control to work and I've tracked the issue down to the Set/Coast switch. The PCM is expecting a 12 V signal ...
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1answer
84 views

How to make this T-flip-flop circuit

I am trying to make a T-flip-flop circuit with a relay, which would: toggle on a button press (12 V) [default state: off] allow control from an external micro-controller (optocouplers) allow ...
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2answers
82 views

Reducing relay contact chatter from bimetallic switch control (AC coil, mains voltage)

I am looking for a few techniques to reduce contact chatter in a relay controlled by a 120 VAC voltage signal. The circuit uses a bimetallic thermal switch to turn a resistive heating element on and ...
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1answer
42 views

Low-side 12V gate voltage driver required for non-PWM application?

Do I require a gate driver IC to turn on my MOSFET BSS138, if I supply 12V DC to the gate of the MOSFET? The MOSFET is NOT being used to switch a PWM waveform. It is simply being used to turn on and ...
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59 views

Schematic review /suggestions: Driving a relay with an Arduino

I am using an Arduino Nano to drive this G5NB-1A-E DC5 relay. My circuit is given below. The BJT (MMSS8050-H) is this one. Is this circuit OK? V_CHIP_REL1_EN is from an Arduino Nano. What things need ...
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1answer
130 views

Design a circuit with relays or switches that has 10 connected devices that can only be powered one at a time

This is my first post here and i was wondering if anyone could help me. I am trying to create a system that will enable me to connect nine or ten 240v devices but only run one at a time. if one in the ...
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2answers
54 views

Reading the input from a relay's NO output over 12 meters

I want to read the input from my driveway gate beam using an Atmega32. I know the gate beam is powered with 12V DC which I get from the driveway gate motor's battery. The beam also has three outputs, ...
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1answer
80 views

4-channel 5V relay module power supply

I am working on home vertical growing project. INTRO I am using: Power supply 12V 20A (https://www.aliexpress.com/item/32983648084.html?spm=a2g0s.9042311.0.0.3af34c4d5hRuZn) Voltage regulator L7805CV ...
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1answer
73 views

Is it possible to use 48V relay in 120V circuit by adding current limiting resistor and capacitor. Will this also speed up the response of the relay?

simulate this circuit – Schematic created using CircuitLab title kinda says it all, Was talking to another engineer and didn't quite follow how they said they could get faster trip coil response ...
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1answer
30 views

Need help in base voltage of N Mosfet in CNC AIr Spray circuit

I'm changing my CNC air spraying circuit. I'm simulating this circuit in Falstad, but I'm not getting what I want... Didn't actually assembled it in real life yet this way. What I need is: When the ...
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2answers
89 views

Controlling relays with logic gates

Pretty new to electrical engineering world, so probably rather simple question. I´m designing control system for tractor trailer hydraulic system. The system is 12 V and solenoids what I am using ...
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1answer
85 views

Connect 400 W LED light to a small relay module

I want to make an automatic relay switch for my LED light for growing a vegetable. The LED says it will use 400 W. I have a small relay module which says 10 A, 250 V, so I think it could handle to ...
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4answers
71 views

Selecting a 12V DC relay for high power applications

I want to know if this relay will be suitable for the following application: Coil voltage will be 12 V DC. The voltage through the contacts will be 60 V DC at 2 A. It is being used to supply power to ...
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1answer
69 views

Is this ringing a problem after "Relay coil fast demagnetization". If so, how to stop

In the question Relay coil fast demagnetisation, a diode and a zener were used in series to quickly remove the energy from an inductor. The question posed an example of a 24VDC 400mW relay, and I ...
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2answers
57 views

Difference between "Rated voltage" and "Max. switching voltage" in relay datasheet

I'm looking for PCB EM-relay for switching 25A 380V load, and there is a lack of models on the market. I have find one of them. The T9G relay has MSV = 480V, but rated voltage = 277V. Also in header ...
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2answers
59 views

Clamping inrush current in a lighting circuit

I use a relay to switch on/off lighting circuits with lots of LEDs. The relay switches the mains supply so must run happily with 110/220/240 Vac. The relay I'm using is rated for an 800 A inrush ...
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3answers
180 views

Relay is not switching in time

My circuit is very simple: it is a 12 VDC battery, a 14.4 VDC charger, 12 VDC power supply and finally devices on load. What I intended to do is to make a UPS system here on DC between the battery and ...
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190 views

Relay coil fast demagnetisation

In the past few days, I've encountered an application note on the Maxim Integrated website about rapid demagnetisation of an inductive load: https://www.maximintegrated.com/en/design/technical-...
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1answer
20 views

car battery to charge deep-cycle (service) battery circuit

I need to connect my car battery (TUDOR TB500) to a deep-cycle battery that I will use for little services (LIFEPO4 12.8V 42Ah). I will put a voltage sensitive relay (that cut in at 13.3V and cut out ...
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1answer
53 views

Clarification on relay withstand voltage

I understand withstand voltage test is to check the insulation of a product, for example between a live metal part (AC input terminal block) and a dead metal part. I saw this specification in one of ...
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1answer
41 views

Multiplexer/Relay - USB Controlled

I would like to measure the voltage of 80 analog outputs of my device but I only have 5 AI available. I am looking for Multiplexer/Relay Board off-the-shelf that is controlled via USB. Is there any ...
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1answer
60 views

Will there be major negative side effects to hot-switching between two mains AC sources that are not in sync?

I am currently thinking about creating a "box" with a wall outlet, solar input and mains source input. This device will use a solar panel to charge an internal lead-acid battery. It's ...
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1answer
64 views

What is the proper way to connect two DC inputs to the same DC output?

I am building a battery charging box for my son's RC batteries. I have a 1000W 24V Meanwell power supply to supply input voltage to a pair of DC chargers. Sometimes we don't have access to AC but do ...

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