| RSS Web Feed for Renewable Energy UK |  | REUK Shop | Directory | Bookmark Site | About Us  

Relay Boards



Relay Boards

Find out about relay boards - what they are, where to buy them, and how to use them

general | electric circuit | electronics
Printer Friendly Version Print Article     

A relay is a kind of switch which is controlled by an electric current. A relay makes it possible for a low voltage low current circuit to switch a high voltage and/or high current device safely - for example, a small battery-powered light detector circuit can be used to control large mains powered security lights via a relay.

Many of the circuits we sell in the REUK Shop and describe in the articles through this website can be used with to control mains powered device such as pumps and lighting with the addition of a suitable relay. For example, our commonest request is for a solar water heating pump controller circuit which can switch a mains powered circulation pump.

Rather than adding a mains switching relay to our circuits directly, we recommend that people use a relay board - i.e. a commercially manufactured circuit board fitted with a relay, LED indicator, back EMF preventing diode, and easy to use screw-in terminal connections. These are now available more cheaply than we can make them ourselves (and if you electrocute yourself with mains electricity we are not liable!).

Relay Boards

The simplest relay board has just one relay, one LED used to indicate the status of the switch, one suppression diode to prevent back EMF from damaging connected electronics, and screw-in terminals for the voltage inputs and for the NC, NO, and COM connections on the relay.

Relay board with one mains switching relay

Pictured above is such a relay board recently offered for sale on ebay UK. Priced at just over £5, this relay board can accept an input voltage of 12 VDC and 24 VDC, will switch mains electricity at currents of up to 8 Amps, and is double pole so you can use it to switch two devices on or off at the same time.
* A screw lidded plastic box was offered for sale at the same time for £3 which would keep everything safely insulated.

For many projects there will be more than one relay required - for example in solar trackers where 2+ (high current) motors must be controlled if the solar panels fitted to the tracker are to follow the Sun's motion across AND up and down the sky. For such eventualities multiple relay (aka multi-channel) relay boards are available. These can have anything from 2 to 16 relays fitted to the same circuit board to make it easy to keep everything safe and tidy.

Relay board with eight relays

Pictured above is an excellent relay board with eight (10 Amps at 250 VAC switching) relays. Each relay has its own transistor and the circuit board has a 12 VDC connection - therefore, just a low-current signal voltage is required to control each relay. This type of relay board is therefore very well suited to microcontroller applications such as PICAXE based projects.

The 8 relay board pictured was priced at £15 plus £3 for delivery (from Bulgaria). Similar 2, 4, and 6 relay boards were also available with prices at approximately £2 per relay.

Computer Controlled Relay Boards

For those with more advanced requirements, relay boards are also available which can be controlled directly by USB or serial connection.

USB controlled relay board - 16 relays

Pictured above is a 16 relay USB controlled relay board* package, sold recently on ebay UK (from Bulgaria) for £50. The small secondary circuit board at the top left of the above picture is the USB adapter board. This is powered directly by the 5 Volts from the PC via USB cable, and has a microcontroller (PIC16F876A) which interprets signals from the PC and opens or closes relays accordingly (via pictured flat cable).
* Note that the relay board itself is simply the 16 relay version of the 8 relay board discussed above).

USB relay board relays controlled remotely over the internet

With this relay board connected to a LAN or internet connected PC, it is even possible to control the relays remotely - conceivably from anywhere in the world - with freely available software or easy to learn BASIC commands!

Buy Relay Boards

If you would like to purchase a relay board take a look first at the latest listings for Relay Board on eBay UK. A second search for Channel Relay often picks up additional relay boards as does Relay Card (which recently found this economical one relay kit pictured below).

One channel relay card kit

For a great value computer controlled 8 relay board kit (8 x 3A @ <25VDC relays) - click here to view this 8 channel relay board priced at £15 + VAT. It comes supplied with Windows software and connects to PC printer port.
Article Last Modified: 15:16, 19th Sep 2008

Comment on this Article

If you have any comments on this article, please email them to neil@reuk.co.uk.


Recommended Related Articles

People who read this article also enjoyed the following articles:

Relays and Renewable Energy
Find out more about relays and their uses in renewable energy applications
Article Last Modified: 10:50, 24th Oct 2008
electric circuit | electronics | general

What is a Transistor
A basic introduction to bipolar junction transistors
Article Last Modified: 11:15, 23rd Apr 2007
electronics | education

Float Switch Water Level Measurement
Find out how to use float switches in renewable energy applications
Article Last Modified: 12:07, 28th Jul 2008
water | electric circuit

Solar Water Heating Pump Controller
Build an electronic pump controller for a solar water heating system
Article Last Modified: 11:33, 9th Jul 2007
water | solar | electronics

LM741 Light Dark Sensor Circuit
Build a light/dark sensing circuit to automatically turn on/off lights and other devices
Article Last Modified: 08:43, 2nd Nov 2007
electronics | electric circuit | general

Solar Battery Charger With LM317T
Find out how to make a current controlled solar battery charger using an LM317T
Article Last Modified: 09:34, 30th Mar 2007
solar | education | electric circuit

Solar Charge Controller
Find out more about Solar Charge Controllers
Article Last Modified: 11:12, 29th Oct 2009
solar | electronics | electric circuit

Reed Switches
Find out more about reed switches and their uses in RE
Article Last Modified: 09:54, 4th Apr 2007
electric circuit | electronics | wind

Automotive Relays
Find out more about automotive relays and their use in renewable applications
Article Last Modified: 10:50, 24th Oct 2008
electric circuit | general

Automatic Pump Shut Off Circuit
Put together an automatic system to switch off a pump when there is no more fluid left to pump
Article Last Modified: 14:54, 19th Nov 2007
water | electric circuit

© 2006-2010 REUK - All Rights Reserved
Page Last Updated on 10th March 2010 at 01:48:33pm

Latest
Articles


Review of Wind Power Peter Musgrove
A review of Wind Power by Peter Musgrove - Cambridge University Press
wind
13:48, 10th Mar 2010

Power Predictor from Better Generation
Find out about the new Power Predictor from Better Generation - solar and wind power data logger
wind
17:24, 2nd Mar 2010

Maximising Air Conditioner Efficiency
Find out how to use air conditioning efficiently
energy efficiency
10:36, 2nd Mar 2010

Energenie 30 Minute Rundown Timer
A device to automatically switch off power to a socket after 30 minutes
shopping
11:35, 27th Feb 2010

UK Renewable Energy Degree Courses
Study renewable energy at university in the UK
education
16:53, 17th Feb 2010

Wireless Electricity Monitors
Up to date details of the wireless electricity monitors for sale in the UK
shopping
16:10, 16th Feb 2010

Investing in Renewable Energy Companies
Invest money in the UK renewable energy sector
general
16:53, 15th Feb 2010

See and Save Domestic Electricity Monitor
Product review of the See & Save Domestic Electricity Monitor
shopping
13:47, 13th Feb 2010



REUK Shop

Popular Items


REUK SUPER TIMER
User programmable 12V powered 10A rated repeating relay timer. 1 second to 99 hours ON and OFF times
£19.99 each.
Complete Circuits



SOLAR PUMP CONTROLLER WITH RELAY
Solar water heating system microprocessor controlled circuit with fitted 10A relay
£25.99 each.
Complete Circuits



12 VOLT 5 WATT SOLAR PANEL
Waterproof 12 Volt 5 Watt Solar Panel with aluminium frame - 290mm x 205mm x 17mm with fitted 5m leads
£33.99 each.
Solar Power



300 WATT POWER INVERTER
Convert 12V DC battery power into 230 AC to power portable televisions, computers, video recorders etc. 300 Watt power rating - peak power 600 Watts
£29.99 each.
Renewable Energy System Parts



CONVERTED PROGRAMMABLE DIGITAL TIMER RELAY
Mains powered programmable timer converted to low voltage with relay board
£21.99 each.
Renewable Energy System Parts



12 VOLT REGULATOR
Supply a fixed 12.0 Volt DC to your devices (up to 1 Amp output)
£4.99 each.
Complete Circuits



MR16 CERAMIC BULB HOLDER
Bulb holder for 12 Volt LED spotlight bulbs
£1.39 each.
Energy Efficient Lighting