Relays

From OpenCircuits
Revision as of 11:45, 5 December 2007 by 216.58.96.135 (Talk)

Jump to: navigation, search

foto porn motorcycle jackets embroidery supply motorola v550 accessories full games free download grannyporn xxx video trailers Products/electro/mgiqun.html nokia 3220 vicerex free chat rooms sun country airline sylvania flat screen tv free sex video clip nu dolce and gabbana estate planning university phoenix machine sex job center plus ohio counties atenolol side effects log cabins crossword puzzle casino slot alltel ringtones special occasion dresses free adult single sites friendship e card sprint ringtones mont blanc pen pictures of anal sex mesa airline bisexual men and women mask france map toyota yaris what are unit trusts electrical engineering careers speedy gonzales yeast infection causes seroquel effect cigarettes personal debt consolidation loan aria giovanni replica movado watch cheapest airplane tickets satellite tv card big tit round ass diapers pinnacle sat driver citalopram hydrobromide huns wreath slot machine career salaries wagering paper doll porn online disney resorts free black sex swingers video united express airline diabetes treatment liver problems miami international airport resume forms bahamas cruise dirt cheap airline tickets criminal checks exterior lighting argentina food mohawk laminate flooring maps satellite henri matisse painting winx disney kid game chuck e cheese coupon debt relief treehouse tv discount furniture outlet milf anal natural breast fake fireplace free anal sex videos asian blow job etodolac christina aguilera free porno movies voip service high schools free cell phone search hardcore orgy car sales remington card game kamagra lesbian sexy wood stove automobile bentley artificial wedding flowers online college degrees missouri newspapers pearl river hilton disabled bathrooms phone number lookup park home insurance girlfriend nina mercedes download songs banks briana national savings bonds globetrotter inn edinburgh fredericks of hollywood home page free ringtones for cricket free hilton paris sex video kathryn macgregor amateur teen sex gaskets addicting game omarion pictures olympus stylus firetrucks sportsbook watch uncut music videos kenalog in orabase sex scenes linen outlet extacy tuning hummer big cock buy denavir online angelz bratz rock philippines news protein diet hawaii air travel vtech phones realestate good sex position t mobile sidekick 2 casting calls birkbeck university of london off road jeep wranglers rack room shoes italian shoes anal gag gift generator medical coding anderson windows ford bronco alltel cellular phone cake recipes thyroid ge auto warranty webcam strippers chanel handbag replica dating internet service jordan shoes collection mp3 file pornoxxx www amr khaled powerrangers cabelas 4x4 offroad buy vicodin big black women rack room shoes free to air buy xenical uk free ringtones for net10 phones downloads sex kannada torrent sexy single man brianna banks sealy mattress swinger sex pictures disney coloring pages benicar homebuilt cnc free funny videos hydroxyzine sex comic nissan pathfinder review men health air portugal sofa bearshare key free antivirus download hotel lancelot rome pantoprazole free screensaver download gift seadoo parts gucci bags diamox pantyhose sex mobile home values country decorating idea birkenstock shoes big black dicks {| align=right |- | Relay |} Description:
A PIC can't source more than 25mA, so how do I turn on/off a light bulb? With a relay!

Relays are those large black boxes that go 'click'. There is a coil inside. When current flows through the coil a magnetic field causes the the internal paddle to move postions. This paddle usually carrys large currents or large voltages.

Most relays have various ratings. We'll start with the coil voltage. '12VDC' for example means that the control coil requires 12V DC for the unit to switch the paddle. The other rating you'll see is '10A'. This refers to the amount of current you can run through the control paddle contact (not the current through the coil). So a 10A relay can handle a load of up to 10A- less than 10A is no problem. What happens if you try to run more current than the max? Well, it will probably work, but at higher currents the internal sparking will tend to burn the contacts. The paddle can potentially spot-weld itself to the contacts in extreme cases.

There are sealed and vented relays. Vented relays tend to run a bit cooler, but are more suceptible to gunk getting into the moving parts.

There are many configurations based on the circuit you need to control. DPDT (double pull double throw), SPDT (single pull double throw) are two of the most common. View the equivalent circuits in the mfg's datasheets to get an idea of how they work.

Relay circuit setup:
When switching large loads, you can get something call fly-back current. These are surges of current when a device is kicked on/off (imagine when the lights dim when you turn on the microwave). Well if it's large enough or often enough, these surges can really kill your board's power supply. The fly

Example Relay Circuit

Many microcontrollers cannot source enough current to feed the control coil. So Q1 is any old BJT (2N3904 is a good one) to turn on/off the relay. The diode 1N4148 (simple, cheap, can handle ~200mA current) is there to supress any fly-back current from entering the main power supply. Be sure to watch how you polarize your diode.

Documents:

Footprints:
SFE Footprint Library

There are various footprints available. Always be sure to do a 1:1 printout of your board and matchup the physical relay to the printout before PCB fab. Sometime the manufacturers list recommended footprints from the bottom view which can lead to mirrored and incorrect FPs.

Manufacturer Info:

Supplier Info:
Digikey part # : G5Q-1-DC12
Single Piece Price : $2.25

Related Items:

Personal tools
Namespaces

Variants
Actions
Navigation
Toolbox