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

learn more… | top users | synonyms

0
votes
2answers
55 views

Beefcake relay control kit - Sparkfun

http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General/RelayBoard-Large-v16.pdf I'm trying to determine the base current of the NPN transistor but keep getting numbers an order of ...
0
votes
0answers
45 views

How to design circuit for robot motor

How to design a circuit which fulfill the requirement below. I am a chemical engineering student which do no have any electrical knowledge but still need to design a circuit for my project. Motor ...
0
votes
3answers
41 views

How to wire a relay?

I recently bought a PCLH-202D1S at my local Radio Shack for my Arduino project I plan on making. I am going to use an Ethernet board with it to make it turn a lamp on or off when a button is pressed ...
0
votes
1answer
18 views

How to turn on gauge lights from multiple sources

I have limited experience with relays, diodes, ect. so I need a little help. I'm currently building a rock crawler (off-road buggy) from ground up and I'm into the electrical and need some ...
0
votes
0answers
42 views

Mechanical Relay Protection (Controlling AC mains devices)

Trying to make a ucontroller controlled relay to switch mains AC devices. It would have a type M plug on one end(to plug in mains socket in the wall) and type M socket on other end(to plug in the AC ...
-2
votes
0answers
26 views

t relay will work to a light up a window display edge-lit acrylic LED sign for three seconds using a general purpose mini reflective Sensor that will [closed]

I am building this a product that will use a general purpose 12v mini reflective Sensor that will lightup a window display edge-lit acrylic LED sign for three or four seconds only when the sensor ...
0
votes
0answers
48 views

how to redesign the circuit to drive a 230V 100W lamp for 5 minutes

I have a circuit , the circuit operates with a siren using a 9v battery the siren used is UM3561 i want to replace the alarm part of the circuit using a RELAy that can drive a 100W 230V lamp for 5 ...
0
votes
1answer
67 views

Switching power to Stepper Motor Drive using relay and arduino

1.This project involves use of stepper motor once in 5 mins to perform precise movement.I m driving the Stepper using L298N-L297 Stepper Motor Driver Board and Arduino UNO. Since the Stepper Motor ...
0
votes
0answers
39 views

Low cost solutions for reversing 130VDC 20A motor

I have a treadmill motor controlled by an MC-60 controller board. The motor is reversible and I want to control the direction using an Arduino. The catch is that it's 130VDC and 17A (the voltage ...
0
votes
3answers
128 views

Relay not switching correctly, controlled from ATtiny85, output to motor

I have an ATtiny85 switching an NPN transistor, which will in turn switch on a relay that will run a motor. Everything is run off a 3.7V 18650 Li-Ion battery, but I have since moved over to a variable ...
0
votes
3answers
40 views

ATtiny85 to control a relay, which will turn on and off a motor

I am trying trying to control a 5V relay (SRD-05VDC-SL-C) with the ATtiny85. I have a simple sketch uploaded (Blink without Delay example): ...
0
votes
1answer
22 views

LPF a digital step to prevent crosstalk?

I'm driving a small signal relay using a pair of pins of an MCU. The problem I experience is noise coupling to the signal being switched. I have isolated the noise from the signal relay and that is ...
1
vote
2answers
72 views

Correct circuit element alternative to transistors

First please see my proteus file to understand what am I trying to do. http://www.docdroid.net/ru27/yenitasarim.pdf.html As you see, there is 5 button groups vertical and 5 button groups horizontal. ...
0
votes
1answer
41 views

Relay-like digital potentiometer?

I'm sure I'm not the first person to want to control an AC motor with their microcontroller and I've found a good relay module to use, however, I still want to be able to control the voltage via the ...
0
votes
1answer
74 views

Driving a 3v Latching Relay with an 1.8v logic MCU Not Working

I have a battery powered device with an 8051-base MCU running off a 3v coin cell (with a DC/DC converter down to ~2.1v). I'm attempting to drive a 3v dual-coil latching relay using two GPIO pins of ...
1
vote
2answers
172 views

ULN2803A Input Pull-Downs

Recently I need use ULN2803A to drive relays. I've never used it before. I have some questions about it. I don't find the leakage information (Icbo) of it. So if the input of it is floating, what's ...
0
votes
2answers
41 views

Location of the relay driving transistors array

I need to drive about twenty realys using ULN2803A. The MCU and the relays can't be locate on merely one PCB. So I separate the relays to another board, and the two boards are connected with wires. ...
0
votes
3answers
88 views

Is a flyback diode needed if there are only inductive components on the circuit (Ex. solenoids)

I'm using relays to drive a circuit of solenoids. Do I really need flyback diodes on the controlled circuit if there are only solenoids on it? The driving circuit is already protected by flybacks. ...
0
votes
1answer
62 views

Is there a technical word for the circuit that a relay turns on

Is there a technical word for the circuit that a relay turns on? In this case the circuit on the right side. simulate this circuit – Schematic created using CircuitLab
0
votes
1answer
50 views

Turn off device when USB power is present

I have a device I'd like to turn off when power is available via a USB socket. The device that needs to be turned on/off is powered by a 12v DC 0.5 amp adapter. USB sockets should have a max 5v 0.5 ...
1
vote
3answers
329 views

Transistor Protection without Diode

I wanted to know if there is a way to protect the circuit from a relay. Usually you add a backwards diode for protection, because when you turn off the relay, the magnetic field in the coil collapses ...
1
vote
1answer
32 views

Reading USB Relay Specifications

Good morning, I am trying to work on some home improvement DIY projects and trying to control light from an RPi / Arduino using USB connection. I've found two possible products, that I think might ...
-1
votes
2answers
70 views

Possible solutions instead of 12 relays

First of all i am new to electronics, but have some basic idea. I want to create a USB switcher with arduino, which will control "where" the usb device is plugged in, instead of unplugging and ...
1
vote
3answers
126 views

Why do electromechanical relay computers tend to use higher voltages?

So I am contemplating building a relay computer. And I have not seen any information on why one would select one voltage over another. It seems that it would be ideal to use 5V relays as that is ...
4
votes
4answers
517 views

Which digitally-controlled chip to replace eight transistors (GE D44C7)?

I would like to programmatically toggle off/on (independently) eight 5 V small light bulbs. It seems that I could use eight transistors controlled by eight independent digital control pins. (See ...
1
vote
1answer
81 views

Using a Contactor or Relay to switch between two DC power sources?

I want to power a motor with a battery, however the complication arises as I want to have two power sources and be able to switch between them. The context of this problem is for an electric vehicle. ...
0
votes
0answers
19 views

Spice model for a latching relay

I need a latching relay model, ideally for DPDT, (http://www.digikey.com/product-detail/en/TX2-L2-12V/255-1782-5-ND/570918) and can't seem to find anything like that. I am hoping some awesome SEer ...
0
votes
1answer
33 views

EM Relay Parameter Calculations

Sometime back I made a relay board to control my table lamp using bluetooth. It worked perfect and so now I would like to upgrade to a beefier power relay. The aim is to be able to control any ...
1
vote
2answers
99 views

Is a relay with a 20 amp rating enough to handle the current from a residential hot water heater?

In Israel the houses usually have a hot water cylinder on the roof of the building which is attached to a solar water heating unit, but which also is connected to an electric heating element which is ...
0
votes
1answer
46 views

Using relay to switch power supply

In my project I use 240 W switching power supply. Due to energy saving and some safety reasons, I don't want this PSU to be on permanently. I'd like to use relay to switch it on and off. However, this ...
1
vote
1answer
72 views

1 switch for 4 circuits

I have 4 basic independent circuits, each circuit consists of 1 x AA battery, some wire, a micro switch and a light bulb. I would like to control them from a single switch. So that upon the first ...
0
votes
1answer
97 views

Can I use a 220v AC rated switch for 220v 120Hz DC?

so I have this setup: Bridge Rectifier has no Capacitors! So it outputs 120Hz DC I had this without the bridge rectifier, but then, since it's AC and you only break one side the current would jump ...
0
votes
1answer
87 views

Connecting pins of Raspberry Pi GPIO in series in order to turn up the voltage

It's unorthodox and probably not recommended by anyone but, for my project of driving a relay only with scrap parts and on the cheap, I managed to get a 12v relay, but, the GPIO ports on the RPi only ...
5
votes
2answers
170 views

Zener Diode Selection for Relay

I am using a Zener diode along with a flyback diode with a relay in order to speed it up a bit. This works very well but I am currently using a rather over-sized zener from the inventory. For ...
0
votes
0answers
43 views

Frequency detection and relay activation

I need a circuit (preferably not using microcontrollers for ease of assembly) to detect a frequency drop in the supply of an electric motor (speed drop) and activate a relay. How can I do this? ...
0
votes
0answers
38 views

Using capacitors to control the speed of a relay loop

Background: In my autoshop class at school we are required to make a circuit that uses relays. When one relay comes on the other one shuts off and it creates a loop in which they switch really ...
0
votes
2answers
64 views

Relay causes USB sound card to freeze

I am using a relay to control a 230 VDC duct fan. Sometimes when the relay turns off my USB sound card freezes, to get it back I have to toggle the power (pull the USB cable, as it is USB bus ...
0
votes
2answers
102 views

DC Motor reversing relays using a micro switch [closed]

I'm looking to use relays and 1 micro switch to reverse the polarity of the circuit. I will need a simple ON/OFF switch to have the motor turning in one direction and then when the micro switch is ...
1
vote
2answers
85 views

Trigger wireless door bell by electrical doorbell

I want to use my electric door bell to trigger a wireless door bell. I replaced the transmit button of the wireless transmitter by a relay and connected it parallel to the speaker of the electric ...
0
votes
3answers
142 views

What's the reason for wiring a relay this way?

I came across the following automotive wiring diagram: One thing I don't quite understand is the way they wired the relay. I've got two main questions. It appears to me that they used the exact ...
0
votes
1answer
112 views

How can I switch power between two hard drives using transistors?

Application I have two hard drives that draw approximately 1.1A / 1.5A on their 12V and 5V power pins. I have several 2SA1020 PNP transistors which are rated 50V 2A and was hoping to use them to ...
2
votes
2answers
74 views

How to allow only 12v

I am looking to control a 12v LED light off of a zwave appliance module. Here is my issue, the zwave module outputs about a 5v pulse every few seconds while in the off state, which is enough to ...
0
votes
3answers
106 views

What kind of component would I need to put a break in a RS-485 bus?

I'd like to have some kind of electronically controlled switch (transistor, relay, solid-state relay, etc) that acts as a break in a RS-485 bus. The effect I would like is to optionally split the bus ...
0
votes
1answer
201 views

How to switch a 220V AC electric bulb using a relay through Arduino?

My aim is to switch an electric bulb operating at 220v AC. For this purpose I use a 12V DC relay that can operate for 220V appliance according to its data sheet. My relay circuit is as under: ...
0
votes
1answer
84 views

Fast Switching For UPS

Well I don't even know how to call this question, but the point is. I am making a DC UPS, and I want to be able to quickly switch from the wall supply to the battery supply, and I don't think a relay ...
3
votes
4answers
112 views

Can someone explain the different Relay schematics contact types?

I'm looking at Relays and there are multiple types of contacts forms, such as: A, B, C, X, Y, Z and much more. searching around found different schematics for same form. can someone explain them or ...
1
vote
2answers
54 views

SSR with low-flow switch to control heater

I'm trying to install a low-flow switch (circuit is open below 0.1 gal/min, closed above that) as a safety measure on an immersion heater, but I have some questions about the setup I've come up with ...
1
vote
0answers
27 views

Fan needs full power to spin up; would then like to have to run off a speed control

Fan in question: http://www.amazon.com/Active-Air-inch-In-Line-Fan/dp/B002JQ4N92 Fan speed control: http://www.amazon.com/Lutron-DVWFSQ-FH-WH-Single-Pole-3-Way-Control/dp/B000MAVHTG The lowest ...
0
votes
1answer
50 views

Combine Lower Gauge Wire to Achieve Thicker Gauge

I have, for some reason, a ton of 30 AWG wire lying around. It's not really thick enough for a lot of applications. Would it be acceptable (and safe) to combine multiple strands of the wire and just ...
0
votes
3answers
134 views

Make a Latching Relay using SPDT Relays

I want to make circuit which can working like a Latching Relay which Hold Current using SPDT Relays. So i can use this circuit to Pules ON/OFF switch. Using limit switch when pressed a pulse goes ...