Tag Archives: Relay

WIFI based appliance module using the ESP8266 and a latching relay


Steve writes:

This is an WIFI-based appliance module using the ESP8266 (ESP12) and a latching relay. The appliance module is powered from the AC line using an inexpensive 5V 1AMP universal input power supply which is attached to the board. There are provisions for local control using a pushbutton switch, and there is an option for a WIFI status LED. The firmware is written in C and the appliance module is controlled using MQTT and JSON.

WIFI based appliance module using the ESP8266 and a latching relay – [Link]

Multi-pole industrial relays provide more possibilities


Switching of three-phase motors or a realization of a sophisticated installation is a breeze with industrial relays Finder.

As we know, a relay is a very versatile component, able to realize also various “sequential” circuits, when for example by switching one relay we´ll switch on a target device and at the same time we´ll enable (or disable) switching of another relay. In these case, it´s an often demand for a relay to have a sufficient number of poles. Majority of such “logic” circuits can be realized even with a common 1-2 pole relays, but it´s not always economical and it also brings another costs for solution of supplying and protection of logic circuits.

Industrial relays Finder series „55“ and „60“ are suitable for a construction of such more complex circuits or for switching of three phase devices.

  • Finder 55 – miniature industrial relay for a PCB or for socket, 2-4 poles, 7-10A (switching current up to 20A), 250/400VAC,
  • Finder 60 – a more robust industrial relay for a socket, 2-3 poles, 10A (switching current up to 20A), 250/400VAC,

Continue reading Multi-pole industrial relays provide more possibilities

Does a universal signal relay exist?


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]

CRYDOM – solid state relays from specialists


Silent operation, immunity against mechanical shocks and magnetic field and other factors make a solid state relay the best choice for many applications.

Where to start? We´ll try to name “pluses” of solid state relays – SSR:

  • long lifetime, no moving parts, no contact burning
  • silent operation, very desirable for commercial and medical applications
  • minimum electrical noise thanks to a possibility of zero-crossing switching
  • easy control (interfacing) and minimum energy consumption to control
  • resistance to shocks and vibrations, installation in any position
  • fast switching (approx. 0.1 ms)
  • low weight
  • immunity to outer magnetic field (usable near powerful motors,…)

Some disadvantage of SSR is, that they generate more heat when conducting a current through “contacts”, than classic EMR. But this is dependent on a switched current. On the other hand – power consumption of the SSR itself is minimal in comparison to EMR of a similar size.

From above mentioned features result, that SSRs are a great choice everywhere, where it´s necessary to switch frequently and/or also to change rotation of motors (integrated in a single component). SSRs are also maximally suitable for switching of DC currents (solar applications, batteries,…) as they don´t suffer by arcing and contact wearing like classic EMRs (DC arcing is much more difficult to extinguish than the AC one). Much longer lifetime in comparison to EMRs result in very low operation/ service costs and significantly eliminates losses caused by eventual downtimes.

If we allured you to SSR, than it´s certainly worth to take a look at products of a leading producer in this field – výrobky spoločnosti CRYDOM, which specializes for development and production of SSRs already for over 40 years. Among novelties in our stock can be found Crydom SSR for PCB in SIP and miniSIP packages, panel mount types, as well as types for a DIN-rail mount. Their basic features are very similar, they differ mainly in max. voltage and current, which they´re able to switch.

Practically each SSR Crydom is available for switching of AC or DC current and also in an “R” version (random switching in any phase of AC voltage) or „ZCD – zero crossing“ switching in “zero” (suitable for minimizing of switching noise).

Detailed specification can be found in the datasheets at jednotlivých typoch and a help at selecting will provide you documents Crydom overview, Crydom product guide, Crydom Selecting SSR and Crydom motion control. The „SSR-the inside story” document is intended for those of you, who like to understand components deeply.

CRYDOM – solid state relays from specialists – [Link]

2 Channel Relay Board


2 channel Relay driver project can be controlled by feeding 2-12V trigger voltage, Very useful project for application like Micro-Controller based projects, Remote controller, Lamp on Off, and any circuits which required isolated high current and high voltage switching by applying any TTL or CMOS level voltage. Two LED works as operation indicator while in , 3 pins screw terminals to connect load and provides both normally open and normally closed switching.

Input: 12 VDC @ 84 mA
Output: Two SPDT relay
Relay specification: 5 A @ 230 VAC
Trigger level : 2 to 12 VDC
Header connector for connecting power and trigger voltage
LED on each channel indicates relay status
Power Battery Terminal (PBT) for easy relay output connection
Four mounting holes of 3.2 mm each
PCB dimensions 49 mm x 68 mm

2 Channel Relay Board – [Link]

1 to 100 Seconds Timer


This project is a timer project and build around popular 555 Timer IC, It can be used for all application required a delay of up to 100 Seconds. Onboard board preset to adjust the required timer duration in range of of 1 to 100 Seconds, Tact switch SW1 to reset the timer and SW2 to start the timer. LED D3 works as power indicator and LED D2 to indicate timer operation.

Load can be connected to CN1 Screw Terminal, Out-put has both the operation normally Open and normally closed. Circuits works on 12V DC and consume approx. 100mA current. Very useful project can be used in various applications like water irrigation system, Kitchen timer etc.

Supply input 12 VDC @ 100 mA
Onboard start and reset tactile switch
Relay output: SPDT relay
Relay specification: 5 A @ 250 VAC
Relay state LED indicator
Preset adjustable range function
Power-On LED indicator
Screw terminal connector for easy relay output connection
Four mounting holes of 3.2 mm each
PCB dimensions 48 mm x 63 mm

1 to 100 Seconds Timer – [Link]

With a step relay Finder 26 can be saved energy and also installation costs


Compact installation step relays Finder 26 series save energy similarly like latching relays, but they also operate on AC voltage.

Step relays are able to effectively control lighting or other devices and they significantly simplify circuit complexity at the same time. If you´re familiar with a bistable (latching) relay, then you know, that a relay can keep its status (On/Off) even without a power supply. A step relay, which we´d like to introduce to you this time, is mechanically significantly different from latching relays, but it also features this energy-saving property – i.e. maintaining the On/Off status even without a power supply.

A step relay is usually available with an AC coil and it´s very simply controllable by one push-button switch (momentary SPST-NO). The principle of the step relay is in the fact, that a driving coil mechanically moves a contact mechanism in various sequences. Each switching of a relay (switching a power to a coil) moves a mechanism in one “step

How to drive a latching relay


Kerry Wong writes:

Latching relay (a.k.a. impulse relay) can be turned on and off by momentarily applying a voltage across the relay coil. The relay would maintain in its last switched state without the need to maintain the coil current. In this post, I will show a simple circuit which can be used to drive such relays. In the video towards the end, I also included more explanations and some demonstrations.
The relay I am using here is a latching RF relay. It is used to switch the input signal between its two outputs. For this particular relay, the input has an APC-7 connector. One side of the output has an N connector and the other side is 50 Ohm terminated. Although this relay is an RF relay, the method I described below is applicable to any latching relays.
Many dedicated ICs (such as MAX4820, MAX4821) can be used for driving such relays. Because of nature of the latching relay, no H-bridge is needed (although you can definitely use an H-bridge, but it would be wasteful).


How to drive a latching relay – [Link]

Why diodes are used around relay coils

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]