[GreenKeys] Solid State relays

[scottjohnson1 at cox.net]

You won't get a SSR to work with a DC loop, as it is two reverse parallel SCR's, it will go on, and stay latched on.  You may be able to use a DC SSR, which uses a MOSFET, but they are generally limited to around 60 V.   SSR's are also not particularly fast.  You can probably make a quick keying circuit with a darlington opto-isolator and a high voltage MOSFET.  Anybody out there tried?  Seems rather easy.

Scott W7SVJ
---- Bruce Gentry <ka2ivy at verizon.net> wrote: 
> Bruce Gentry wrote:
> > Larry Tighe wrote:
> >> Howdy Folks,
> >>
> >> I have a solid state relay, rated at 240 VAC, 20 amps.  It can be 
> >> keyed with 6 VDC.  I put the ohm meter (analog) across the AC 
> >> terminals and it opens and closes the "switch" with 6 VDC.
> >>
> >> I tried to key a tty loop with it and it won't close the circuit.  
> >> Anyone tried playing with these successfully?  For now, I can't 
> >> understand why it would show on an ohmmeter with probably 3 volts 
> >> from the meter and then not close with 130 VDC and a 60MA magnet.
> >>
> >> lar
> >> Larry
> >> K2JIA
> >> OFC
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> >>   
> > A major use of solid state relays is  industrial and elevator control 
> > equipment to replace  electromechanical relays   powering motors and 
> > inductive loads. Because there are no contacts, nothing is eroded to 
> > wear out and fail or stick. Also, the cut off is clean and there are 
> > lower transits put onto the power line.  Fewer service calls, but the 
> > flash and bang show is gone too!  The solid state relay uses scrs or 
> > triacs to carry the load, usually with a small IC included to trigger 
> > the devices at zero point so they are not switching  in the middle of 
> > the wave.   For a teletype loop, look into high voltage MOSFETs or 
> > IGBTs.      Bruce Gentry
> >
> 
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