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The only problem with SSR is you need an appropriately sized heatsink whereas a standard relay does not. However you can't drive a power relay directly from a PIC. Either way has it's advantages and disadvantages. Also you can get SSR zero-cross switching built into them. This is really nice for switching inductive loads like motors.
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Dont want to steal the thead, but,
i have one 5v relay ( EDR201A0500 ) and it can switch up to 250VDC.
My question is, with this relay can i connect the pic directly to the relay ( no transistor required ) ?
Edit:
http://www.ece.com.tw/product/relay/edr/edr.htm
It does say "The high sensitivity allows direct driving by TTL", so it means i do not need the transistor. And this is a cheap relay (2.5 euros )
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Last edited by ruijc; - 5th March 2008 at 17:10.
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I personally switch all relays with a transistor. Even the little zero-cross SSR we use require 20mA to work properly.
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Hi ruijc,
I=E/R so I=5volts /500 ohm coil so I=.01amp or 10 ma. Unless my calculator lied it should work, make sure to install a diode to protect the port from back EMF.
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
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Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
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There simply is no "Happy Spam" If you do it you will disappear from this forum.
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For driving relays I use an NPN darlington array DIP. Drive 8 relays for $.72 and has the diode built in to protect the pic from inductive spikes. If you are going to do home automation you will probable need many channels and these work very well.
see: ULN2803APG
http://search.digikey.com/scripts/Dk...=ULN2803APG-ND
OOPS I see Jerry already recommended a darlington driver, let me change my answer to "I agree with Jerry on the driver chip"
Last edited by krohtech; - 5th March 2008 at 19:52.
Best Regards,
Kurt A. Kroh
KrohTech
“Goodbye and thanks for all the fish”
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