RE: 24 Volt 1-Wire dry contact relay??

Dear Matt - Re:  "Should the diode be connect across the relay load or the
relay coil?".

ACROSS the relay, such that the diode allows the voltage (Back EMF) to
discharge back though the relay coil itself...  Depending upon the SIZE of
the relay, you might want to use a 1N4001 (1 AMP) diode, or a 1N4148
(available from RadioShack - $2.59 for 50)). Small relays will probably need
a 1N4148 diode).

A good explanation is here on "Back EMF":

http://www.newton.dep.anl.gov/askasci/phy00/phy00351.htm

You might be interested in this also from Taylec (relay boards that work
with the Systronix 8x1-wire board),

http://www.taylec.co.uk/acatalog/index.html?http%3A//www.taylec.co.uk/acatal
og/Taylec_Ltd_Products_1_wire_Boards_24.html&CatalogBody

Best regards, Kelly Smith

-----Original Message-----
From: Matt Chapman [mailto:matthew.chapman-HKixBCOQz3h+cjeuK/[email protected]]
Sent: Wednesday, June 23, 2004 5:05 PM
To: [email protected]; tini-6tN4nzCoH/[email protected]
Subject: Re: [TINI]24 Volt 1-Wire dry contact relay??


Should the diode be connect across the relay load or the
relay coil?

Thanks,

   - Matt


Kelly Smith wrote:

> All - And be sure to add a "back-EMF kickback" diode strapped across the
> relay, or you will blow out the DS2406 on the 8x1-Wire board (cathode goes
> to the relays +V).
>
> Best regards, Kelly Smith
>
> -----Original Message-----
> From: tini-admin-6tN4nzCoH/[email protected] [mailto:tini-admin-6tN4nzCoH/[email protected]]On Behalf Of
> Bruce Boyes
> Sent: Wednesday, June 23, 2004 9:59 AM
> To: Joel Rowley
> Cc: tini-6tN4nzCoH/[email protected]
> Subject: Re: [TINI]24 Volt 1-Wire dry contact relay??
>
>
> At 06:52 PM 6/22/2004 -0400, Joel Rowley wrote:
>
>>Hey List,
>>
>>I am looking for a 24 Volt 1-Wire dry contact relay.  What I mean by this
>>
> is
>
>>that the relay can handle 24 volts going through it, not that the relay is
>>powered by 24 volts.  Do any of you know if there is something like that
>>
> out
>
>>there or not?
>>
>
> You can purchase these at DigiKey and connect them to an 8x1 Wire board as
> long as the relay coil can be powered by 12 volts or less at 50 mA or less
> so that it can be driven by PIOA from a DS2406.:
> http://www.systronix.com/expansion/8x1wire/81w.htm
> and
> http://www.systronix.com/expansion/8x1wire/DS2406_relay_drive.pdf
>
> Regards
>
> Bruce
>
>
>
>>Thanks!
>>Joel Rowley
>>
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