Electrical Engineering

Questions tagged [relay]

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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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Finding relay datasheet: HC1-AC240V LR42758 30111H AP311998 3A30VDC 10A 1/3HP 125,250VAC

I have a dickens of a time finding a datasheet for a spare relay that I want to reuse. Here are the images of it: The text from the side there is: HC1-AC240V LR42758 30111H AP311998 3A30VDC 10A 1/...
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45 views

UPS on DC lines

How could a UPS switch between battery and AC wall socket fast from around 4 ms to 12 ms. What make it especial to switch in that very low time. As far as I know it has relays inside it to perform the ...
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27 views

ULN2803 relay driver working for high loads

I am trying to understand the working of this Darlington transistor array. I am using it for inductive loads and for driving the loads of my relays, but now I am trying to understand the part of its ...
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4answers
65 views

Using a 555 timer and 14-stage binary divider for 2 hour timing circuit

I am researching how to design a timing circuit that will activate a relay with a push button and deactivate the relay after two hours. My understanding is that I can feed the output of a 555 timer to ...
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35 views

Powering a solenoid valve with a relay and no external power source

I have a solenoid valve (12VDC, 540mA) that I would like to control with a 5VDC relay (15A SPDT). Is it possible to power the solenoid without an external power source seperate from the one powering ...
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2answers
55 views

Make a Latching double pole single throw relay, using electronic components

I am latching a DPST relay. So I made a prototype using some transistors(ex. BC547) to enabling and disabling the latching. But I want to know whats the correct way of doing it. I have both 12V and ...
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45 views

Why does the UPS mode of an inverter have faster switching times?

Of all the sinewave inverters I have used, they contain a switch at the back labelled Normal and UPS. When you put the inverter in normal mode, there is some 40-50 ms switchover time, enough to make ...
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35 views

esp32 relay control

I'm designing this circuit for my esp32. I need to control 2 dpdt relay 424012. One is on the board, the other off board. This relay controls both 220 V and 12 V lines. I'm using 2n2222a for switching ...
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2answers
26 views

DIN Latching Relay

I am new to relays, and trying to read up. My needs are a relay that can control 230VAC min.10A(pref. 20A). It should be controlled by a 5VDC signal. One 5VDC pulse(0VDC->5VDC->0VDC) should trigger ...
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2answers
61 views

Would a capacitor between base and emitter make relay amplifier less noisy?

I have a single transistor relay amplifier driven by GPIO output of Raspberry PI. The amplifier works reliably and is not causing any immediate problems. Still, if I leave the relay flipping on/off ...
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1answer
55 views

Doorbell hack - remote unlock door

We need to use the audio output of a wireless doorbell to trigger a stable DC voltage which is going to keep switched a 3.3V DC relay as long as the audio output is present. The relay is supposed to ...
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2answers
36 views

Circuit for reversible motor controlled using relays

I am very new to electronics and drawing isn't my strength either, so please forgive the bad diagram. But I hope it makes sense. I want to be able to control a motor using relays and be able to ...
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40 views

Lipo Charging Circuit- Relay vs MOSFET

I am currently working on an application which will use both a Lipo and an external power source (DC). The external power source will charge the lipo as well as power the system load at the same time (...
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3answers
57 views

Calculate resistor value of Optocoupler & Transistor

I have a problem working out the values for the resistors R1 & R2 of a relay module. Right now, I use R1 = 1k & R2 = 560 Ohm, but that is not working. What resistor values should I use? And ...
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1answer
68 views

Relay voltage at higher voltage with no current

If you use a 220V relay to switch 400 volt but without drawing any current (no current will pass through the relay) is it ok?
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1answer
54 views

Linear Actuator using Relays, MOSFET, and PWM

I have a 29V Linear Actuator that I want to control - both direction and speed. For the direction I used this 4-channel relay module, but I only used 2 relays on it. I was able to successfully ...
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0answers
38 views

Open circuit showing 1-15MΩ of resistance on multimeter

I'm trying to understand a phenomenon I observed while troubleshooting a system. There are airflow sensors with wires connected to common and normally open so that the circuit closes when air is ...
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1answer
125 views

2n2222 can not make it work as gate

simulate this circuit – Schematic created using CircuitLab I am trying to make a simple switch with the 2N2222, so i can send 5 volts from a 3.3 V output pin on an arduino/raspberry pi. I have ...
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0answers
37 views

Looking for a relay

I need to find a relay that allows me to set a defined voltage for the input before closing the output/contacts of the relay. Here is my scenario. The circuits is in DC voltage. I have a pedal in ...
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1answer
63 views

Is there a relay package which can be triggered by a numeric coded pulse?

I would like to design a simple relay which is triggered by a series of pulses rather than just a high signal. e.g. the relay would have a serial data input. The relay would need to be "preset" with ...
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2answers
81 views

Reduce/Remove Sparks in AC and DC Contacts of Relays

I see that there are sparks being generated whenever there is a connection established between two contact points in the relays. So is there a way to reduce/remove those spark generated in the relays.
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1answer
40 views

IRF520 as a relay driver

I am trying to use IRF520 as a relay driver for ESP32, but by reason unknown it does not works. I have replaced it twice with a new ones, but yet it keep not working. I have 3V on the ESP32 pin when ...
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Relay for rollershutter motor

A few years ago, I build a controller for our garden door rollershutters (2x 2m wide), 230VAC 2xL-N controlled. In some initial tests, the inductive load killed the cheap mechanical relays found on ...
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1answer
32 views

Double DC Motor Compressor Circuit Protection

I'm a mechanic! So, please do not blame me for stupid questions. I did a lot of research using relays for switching DC motors. The following circuit is showing the current version I want to realize ...
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2answers
76 views

Can I drive 3.75 V / 370 ohm coil relay from Raspberry PI GPIO output?

I have discovered that there are relays like these available on the market that trigger at 3.75 V and have coil resistance above 370 ohm. I assume this would mean about 14 mA or about that might be ...
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1answer
24 views

Can I turn on a relay OUAZ-SS-105 from high on P26

Is it possible to turn on a relay OUAZ-SS-105D using a high on pin 26. See image Case 1: if I replace the P26 connection with a wire to vdd the led "GOES ON". The vdd voltage is 3.3 volts. Case 2: ...
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61 views

Is there an easier way to signal this active low relay module for the pi?

Two parts to this question: Part 1: I am planning on setting up this relay module with my pi (which afaik has gpio pins set to LOW at startup). 1.) Does this mean if I hook it up as the picture ...
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1answer
44 views

Switching several relays at the same time parallel with one or several transistors?

I need to switch 2 or maybe 3 or 4 relais at the same time. Is it best to have for each relay a separate transistor? Or is it perfectly fine to use just one transistor and one diode for several ...
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53 views

Is there an inexpensive multi-pole, multi-position relay?

One of my projects consist of being able to redirect audio output from one among several PCs to one among several audio devices such as headsets, speakers or audio recording devices. The redirector ...
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0answers
27 views

SSR selection for dc controlling ac

Hi I am trying to create a circuit that turns on automatically when a multi pin pannel plug is connected (specifically a Weipu connector). The idea is that the 3.3V dc voltage is used to control an ...
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1answer
53 views

Relay back emf cauisng my micro controller reset

I have a 5V 30A relay in my circuit. I made a PCB with all the connections to microcontroller and relay. At present I am using M7 smd diode as flyback diode. But problem is occuring if I switch on/off ...
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1answer
30 views

Dynamic residential power system

I have a farm with solar panels. Right now, it is powering the house, and excess gets sold to the electric company. I was thinking that instead I could have the excess power bitcoin mining equipment. ...
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45 views

Relay module and Arduino Isolation; How to acheive?

I'm going to control a 3phase motor with an Arduino Pro mini and and a 1 Ch. relay module. In numerous articles it's been advised to separate Arduino and relay module's Vcc. For sure, the second ...
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3answers
97 views

What does it mean to soft switch a relay?

I am specifying a relay I/O card for a Beckhoff PLC. (Link to an overview of Beckhoff digital output slices, scroll to see Relay section) Some of the relays have ...
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68 views

Is there a way to switch between circuits without a relay?

So I'm trying to create a mobile phone charger inside an Altoids mint can, It uses two Panasonic NCR18650BD which have a discharge of 10amps. Anyways, I have it set up in parallel. It uses a zener ...
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3answers
33 views

Regulated input relay switch

simulate this circuit – Schematic created using CircuitLab The control input may vary. What I want is, the relay will only switched on if the input voltage on R1 is at least 5 V. It works but ...
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1answer
37 views

Raspberry Pi gets rebooted by an isolated circuit that has a relay (nodemcu)

I have a Raspberry Pi that is powered by mains from a AC-DC Laptop Charger (with DC Buck regulator). I also have a DIY Nodemcu (Home Automation project), it has a relay (5V with a control circuit ...
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41 views

Using a HT12D pulse to drive a latching relay

I am receiving a signal via RF and using a HT12D to decode it and send a 5V DC pulse. I want to use this pulse to drive a latching relay. On the first pulse it will make the relay latch in NO ...
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1answer
31 views

Reverse Polarity Protection relay calculation

i want to make reverse polarity protection without voltage drop ,i was searching and i found this https://www.edn.com/design/analog/4368527/Simple-reverse-polarity-protection-circuit-has-no-voltage-...
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1answer
75 views

Transistor in the Darlington pair getting burned?

I have a relay board controlled by an STM32 to switch two AC loads (a compressor and an MD40 pump). The circuit seems to work fine but after about a day of operation, my BC847 got burned and the ...
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1answer
67 views

The LDO on my STM32 circuit heats too much after long hours of operation

I have an STM32F0 based circuit to control two AC loads (a compressor unit and an MD40 pump). A 12V supply feeds the circuit. On the PCB there is an LM2576T to step the voltage down to 5V. This is ...
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56 views

Why this contact has some leakage voltage?

I have a relay circuit ,the input is 30V DC . Relay switching is work well(output has 30v dc while relay switch from NC to NO). But relay output(P2) has some voltage without relay switching from NC ...
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1answer
21 views

Can I use solid state output and relay output with the same components?

So I have a OTB1E0DM9LP Schinder Electric I/O distributed module and I want use it'output to control some 24v electro-valve's and some 24V contactors. The module have 2 Solid-state outputs of 24V 0....
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0answers
29 views

Increase signal voltage before Raspberry Pi

Another newbie question. I want to send a signal to a raspberry pi zero but I don’t have enough “signal-power” I have a Adafruit Powerbooster 1000c. It basically takes power from a micro USB, a ...
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1answer
50 views

15 second switching circuit

I am designing a circuit that receives a signal from a motion sensor, and then turns on a light for 15 seconds. I have a rough idea on how to make the circuit, but I am also curious what are the ...
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29 views

I need sensing ADC use mux with stm32

There is an LED connected in parallel. If one LED is damaged and the ADC value reaches zero, the MCU detects this. So I designed the circuit using a multiplexer for this logic. However, it is ...
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0answers
54 views

Socket with an embedded relay for microcontroller

I'm working on a project to test device charging. The idea would be to use a micro to turn the socket the charger is plugged into on and off. I need 10 of them so I was wondering if there is an off ...
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2answers
88 views

Can't work out Arduino 12v Relay (5v Logic)

I have a 12v relay but I just can't figure out how to use it. I went to tech support, but they just waved me away. So, my problem is that I have an 8 channel relay, but can't get it to work. I did try ...
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2answers
63 views

Is it correct to place the base to emitter resistor in a BJT circuit as follows?

This is a follow up Question to What is use of R41 (base to emitter) resistor in Transistor Relay Circuit? My doubt is can we connect the resistor R41 between emitter of optocouler and GND? The ...
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2answers
48 views

Current through relay

I want to control AC power switch 230vAC, I used this relay type Relay OJE series SPST. According to the datasheet, it can drive V=5v and the resistance through the coil is 125 ohm I calculated to get ...

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