Anyone know a good cheap relay for 120VAC loads

On Tue, 30 May 2006 23:34:31 GMT,


You might want to look into one of the parallel port relay boards
like below and use it attached to your AVR instead of the
parallel port.

http://www.electronics123.com/s.nl/it.A/id.446/.f?sc=8&category5
http://electronickits.com/kit/complete/elec/ck1601.htm
http://store.qkits.com/moreinfo.cfm/QK74A

This looks like it might work for you:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G1619

http://oeiwcs.omron.com/webapp/commerce/command/ProductDisplay?prrfnbrU4&prmenbr16

They call it a GBC but I think it's probably a G6C relay.  The spec says
200 mw so I assume that means 40 ma at 5V.  But I could be wrong about the
current or the part number.  But at $.99 each, you can buy a few and figure
out it they work for you.

Ah, here's another data sheet that does say 40 ma for the coil at 5VDC:

http://oeiwcsnts1.omron.com/ocb_pdfcatal.nsf/PDFLookupByUniqueID/3BEA0E52DDFDE22286256FC7005D0130/ $File/D20G6C0305.pdf?OpenElement

--
Curt Welch                                            http://CurtWelch.Com/
curt@kcwc.com                                        http://NewsReader.Com/

http://oeiwcs.omron.com/webapp/commerce/command/ProductDisplay?prrfnbrU4&prmenbr16

http://oeiwcsnts1.omron.com/ocb_pdfcatal.nsf/PDFLookupByUniqueID/3BEA0E52DDFDE22286256FC7005D0130/ $File/D20G6C0305.pdf?OpenElement

Oh, man.  That is the perfect answer.  I asked the question yesterday, and
here you show me the exact thing I need, for very cheap, $0.99 ea.  Get
this, I just finished ordering 12 of that exact same relay from DigiKey for
$5 each!  If I'd read your post first, I would have saved $50.  Live and
learn.  At least now I know where to get replacements if I need 'em.

Anyway, thanks for the fine example of how Usenet adds value.  That was
probably the most prompt and appropriate answer I've ever gotten on Usenet.

Mike Ross


Mike Ross
--

You're gonna run into problems if you try to drive [too many] relays
directly off an AVR or PIC chip, esp as many as 12 relays. Besides load
currents in individual pins, you also have to look at the max load on
the chips.

What you want to do instead is insert a couple of ULN2803 darlington
driver chips between the uC and relays. The drivers are cheap, under
$1, and they only require 1 mA or so current from the uC, plus they
have integrated clamping diodes for the relay coils [absolute
necessity], plus they also add an extra degree of isolation and
protection for the uC. Better to blow a $0.50 part than a $5 uC chip.
This is really the best way to go.

Also, you can buy relays cheap from places like electronic goldmine,
but these are usually surplus items, and they'll likely not have the
same parts next time you go back. Digikey will have the same
replacement parts 99.9% of the time.