by w2aew @ youtube.com:
Today’s “Back to Basics” tutorial topic – why flyback or snubber diodes are used around relay coils when switched or controlled by low power electronics. We’ll talk about how and why dangerously high voltages can be generated from the collapse of the stored magnetic energy in the coil when they’re switched off, and how the diode can protect the low power electronics from being damaged by these high voltages. Some voltage and current measurements are made on an actual circuit to see the real-world effects.
Why diodes are used around relay coils - [Link]
This project is an one Channel Relay Driver suitable for a variety of projects. Check specifications on the page below.
One Channel Relay Driver - [Link]
8 Channel Relay Board is a simple and convenient way to interface 8 relays for switching application in your project. Input voltage level support TTL as well as CMOS. Easy interface with Microcontrollers based projects and analog circuits.
8 Channel Relay Board - [Link]
You are planning to use Arduino in your project but you need some kind of remote control functionality. A standalone Arduino won’t provide what you need but this DIY shield may be a good solution for you. It includes a 433.92Mhz RF receiver which lets you send commands to Arduino wirelessly and four SPDT relays which can be used for switching purposes.
Each relay is capable of switching up to 10A @ 250VAC so they can be used to control mains powered devices. There are four LEDS indicating the status of the relays. The terminal blocks on the shield lets you easily connect the devices you will control.
The RF receiver is a module that can be found in the market easily. It is directly soldered to the shield and runs at 4800bps. The board has an antenna input which lets you solder your custom antenna to increase the wireless range.
DIY 433MHz RF Receiver and 4 x SPDT Relay Shield - [Link]
Remote control your electrical devices through your local network or internet. The circuit contains one output (Relay) and one input (isolated input). The whole project was built by using arduino nano platform and an ENC28J60 ethernet module. It can be used the W5100 ethernet module instead of ENC28J60, by replacing the UIPEthernet library to Ethernet library.
Moreover, the control is made from the Android application I wrote and it’s available on Google Play (https://play.google.com/store/apps/details?id=com.serasidis.NetworkRelay).
The schematic diagram, arduino sketch, photos and demonstration video is on my web site:
Arduino Network relay - [Link]
To tell the truth, probably no, but we have for you a few hints for relays which are very close to an ideal.
Signal relay is almost an „ideal component“ thanks to a practically zero distortion and a total isolation of a switched signal from a control one. That is naturally one of the main features of all electromechanical relays, but at signal relays it´s especially valued, as we usually require switching of relatively small signals. Favorite and widely used are for example relays Fujitsu series B3 and B4 (miniature SMT and THT relays) and series AxW (miniature only 5mm high relay) – all with bifurcated gold-plated contacts for a high reliability.
A novelty in our portfolio is the series Fujitsu NA representing something like a “golden middle way “. With dimensions 7,4×14,9×9,7 mm it belongs to narrow miniature relay enabling a high density of components on a PCB. Even though relay NA is somewhat bigger than for example series B4, but it´s able to withstand higher AC current – up to 0.5A/125VAC (vs. 0.3A at series B4) and it also provides an extreme mechanical lifetime up to 100×106 , what´s approximately twice that of B4 series. Sensitive coils, with a consumption of 0.1-0.3W at majority of types enable a dense mounting without problems with overheating.
From the point of view of the lowest possible consumption are naturally the best latching relays (with a permanent magnet) controlled only by pulses. Usually they´re easy to recognize by a letter „L“ behind the series marking (for example NAL, JSL). In a Fujitsu signal relays overview and the Fujitsu catalogue can be easily found a comparison among particular types as well as detailed information about them. We try to keep the most favorite types always on stock, what´s also reflected in the substantial increasing of stock.
Does a universal signal relay exist? - [Link]
This is a 8 channel relay interface board using ULN2803. All the relays are opto-isolated using optocouplers and can be controlled directly using a microcontroller of any kind (Arduino , 8051, AVR, PIC, DSP, ARM, MSP430, TTL logic) or a PC.
It’s easy to manufacture and have three pin screw terminals for easy connectivity.
8 Opto-isolated Relay board - [Link]
by Viktor Safronov:
Sometimes you may need a group of switches where, if any switch is activated, it deactivates the previously active switch. This Design Idea implements such a function with relays.
This “one and only one” function is often implemented as mechanical switches in which an actuator (usually a movable metal bracket) is used to switch contact groups on and off. When any switch is pressed, this bracket first deactivates all switches, then activates the pressed switch.
Exclusively select 1 of N relays - [Link]
With its width of only 5mm is this relay able to switch 6A/250VAC, moreover at a minimum coil power consumption.
Thin as about a block of “Domino” and still so powerful and for a reasonable price – these are narrow relays series FTR-LY. Powerful and still so easily usable even in circuits with a 5V logic … Somehow this way could be described the well proven relays of FTR-LY series.
If you´d like to use a relay of this shape, then the FTR-LY series will probably also fulfill all your expectations regarding lifetime, reliability, low power consumption and other. When selecting a suitable type, it´s good to take in mind a material of contacts – on stock we keep three types (5V, 12V and 24V DC). A novelty in our portfolio – type FTR-LYCA005V has a „V“ suffix, what means AgSnO2 + Au (0.3µm) contacts. The biggest advantage of a golden layer on contacts is a very low minimum switching current through contacts (10mA/5VDC), in comparison to types with a suffix „E“ or „Y“, which have a minimum switching current 100mA/5VDC. Types FTR-LYCA012Y and FTR-LYCA024Y have in summary the same good properties, only they´re not suitable for switching of currents below 100mA (worse self-cleaning ability of contacts).
An advantage is up to 4000VAC (coil/ contacts) isolation and an isolation distance (clearance/ creepage) is 8/ 8 mm. To a reliability even in tiny areas on a PCB also contributes a max. operating temperature up to +85°C and a low power consumption (approx. 170 mW). Types, which we keep in stock are with one changeover contact (1CO, SPDT), that´s why they can be freely used in application where you need an NO or NC contact.
Upon order, there are also available types for socket and the PCB socket (JM-6N). It´s beneficial for applications, where we want to maintain a possibility to easily exchange a relay.
Detailed description can be found in the Fujitsu FTR-LY datasheet.
Narrow but strong – relay Fujitsu FTR-LY - [Link]
Finder monitoring relays are able to effectively signalize a fault status in a mains line and to prevent damages or undue wear-out.
Too high or too low voltage, phase loss or a wrong phase rotation are conditions commonly occurring in an industrial environment. Even though a phase rotation is usually stable, but only one improperly connected lengthening cable is sufficient …. These fault conditions harm to typical 3-phase devices like for example motors and as for a voltage out of tolerance – this usually doesn´t make well to any device. Devices like compressors and gas discharge lamps even don´t like too often switch on/ off (cycling) in case of fault conditions in the mains power line. There is a solution for all these cases – in a form of a simpler of a more sophisticated monitoring relay.
In our offer can be found high-quality components from company Finder – a producer with long-term experience in production of relays. To components intended for monitoring of mains line belong for example series F70 and F71, from which we keep in stock these types:
● 184.108.40.2060.2022 – 3-phase electronic monitoring relay. Monitors low voltage (adjustable), high voltage (adjustable), window mode (low + high voltage), adjustable time delay of switching (trip), selectable fault memory, phase loss, phase rotation. Comprehensive indication of all statuses by means of three LEDs
● 220.127.116.110 – compact 3-phase electronic monitoring relay. Monitors phase rotation and phase loss.
● 18.104.22.1680.1021 – 3-phase monitoring relay. Monitors low voltage (adjustable), high voltage (overvoltage), adjustable time delay of switching (trip), selectable fault memory.
All above mentioned types have on their output a small relay (6 or 10A), which can serve for controlling of a main contactor or directly for switching of other devices in case of faulty status. Adjustable time delay at types 70.31 and 71.31 functions in a way that after detection of a fault a relay “waits” for a selected time and if a fault still persists, the relay will switch on an output contact. In other words – monitoring relay ignores faults shorter than a selected time (0.5-60s at type 70.31 and 0.1-12s at type 71.31). This function is very useful to prevent an undue frequent switch on/off of devices, which are able to withstand a short-time fault status without a damage.
Memory function is also a useful function, which – if active, will prevent a repeated start of a device. This is very important for example at devices, which mustn´t be switched on without an operating personnel.
Detailed description can be found in datasheets at particular types.
Relay Finder will let you know, when one phase is missing … – [Link]