If the SSR states VAC on the terminals then it needs it for the Triac inside to work. The Triac needs to see a zero volts crossing to switch on/off, which doesn't exist w/ DC voltage. Learned that one that hard way while building my CNC :)

Fwiw

J. Johnson

> Not certain, Dave.
>
>
>
> If it were a mechanical relay then it would be fairly easy to say
> "yes' or
> "No" - solid state is a bit more complex.  However, I am inclined
> to believe
> that when they specify AC voltage on the controlled side that they
> mightmean it.  Here are two relays from FuturLec that look
> identical.  Note that
> the first one implies the load should be AC voltage while controlling
> voltage is DC.  Then notice the next photo for DC/DC relay. 
>
>
>
> This at least implies to me that perhaps with solid state relays -
> it may be
> significant whether you specify DC on the controlled side as to
> whether the
> solid state relay functions.  For instance it might require the
> voltage to
> be alternating and would see DC voltage as no-voltage?
>
>
>
> SSR10A - SPST 3-32V 10A Solid State Relay
>
> SSRDC100V40A - SPST 0-100Vdc 40A DC Solid State Relay
>
>
>
> They can be found at:
>
>
>
> http://www.futurlec.com/RelSS.shtml
>
>
>
> Ed Anderson
>
> Rv-6A N494BW Rotary Powered
>
> Matthews, NC
>
> eanderson@carolina.rr.com
>
> <http://www.andersonee.com> http://www.andersonee.com
>
> <http://www.dmack.net/mazda/index.html>
> http://www.dmack.net/mazda/index.html
>
> http://www.flyrotary.com/
>
> <http://members.cox.net/rogersda/rotary/configs.htm>
> http://members.cox.net/rogersda/rotary/configs.htm#N494BW
>
> http://www.rotaryaviation.com/Rotorhead%20Truth.htm
> <http://www.dmack.net/mazda/index.html>
>
>  _____ 
>
> From: Rotary motors in aircraft [flyrotary@lancaironline.net] On
> Behalf Of David Leonard
> Sent: Wednesday, June 24, 2009 12:20 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: Relay Woes
>
>
>
> I think I may have found the answer on page 10 here (although for
> a slightly
> different relay).
>
> http://www.components.omron.com/components/web/PDFLIB.nsf/0/77056031AB352221
> 85257201007DD66B/$file/D20G3NA1205.pdf
>
> If so, is that diode symbol reversed?  wouldn't that cause a short to
> ground? Or do I need to install my pump so that the relay
> completes the
> circuit to ground?  Aaah, yes, thats it... will require an extra
> wire out to
> the pump (located in wing).  Still I dont really get it.
>
> Dave Leonard
>
> On Wed, Jun 24, 2009 at 8:34 AM, David Leonard
> <wdleonard@gmail.com> wrote:
>
> For you EE types, I have a question.   I am installing a smoke
> system and
> wanted to use a relay to control the pump.  I bought this relay
> from Mouser
> that I thought would do the trick:
>
> http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtLEhJ5P%2fNsZ6b
> nrz6%2f%252b%252bJvA50eSiydqPQ%3d
>
> The problem is that if there is any load (like the pump or even
> the 0.02A
> indicator LED I installed, then the relay will not turn off when I
> turn off
> the signal voltage.  So either I do not understand how to use the
> relay, or
> I chose the wrong relay.  I have checked my wiring in-so-much as
> to confirm
> that the signal voltage does turn on and off with the switch,
> voltage across
> the 'LOAD" terminals does disappear when there is no load but not
> when there
> is a load (current). 
>
> Is it possibly because this relay is designed for an AC load?  Other
> suggestions?
>
> --
> David Leonard
>
> Turbo Rotary RV-6 N4VY
> http://N4VY.RotaryRoster.net
> http://RotaryRoster.net
>
>
>
>
> --
> David Leonard
>
> Turbo Rotary RV-6 N4VY
> http://N4VY.RotaryRoster.net
> http://RotaryRoster.net
>
>