Solid State Relays and EMI

I'm using some solid state relays, and having some problems with (I believe) EMI.
http://www.cel.com/pdf/datasheets/ps7141a.pdf
I'm using this part in the B and C configurations.
These items are located near some RF sources operating at about 148MHz. During transmit (.5W power), I'm getting some false "on" states. I'm pretty sure this isn't due to the equipment on the load side, as removal of the SSR's eliminates the effect.
1. Anyone know if these type of SSRs are subject to EMI that can cause false on-states? 2. Would induced AC voltages (from the RF source) in the load lines (around 148MHZ) decrease the R-off resistance? 3. If the problem is in the SSR's, anyone have any suggestions regarding how to lessen/prevent this? (EMI shielding, other PN's that are immune to this, inductors/caps that could be placed in the load lines, etc).
Thanks for your time! Dave Harper
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David Harper wrote:

Be advised that relays made with copper (a *solid*), iron (a *solid*), sometimes plastic (a *solid*) and sometimes glass (a *solid*) ARE SOLID STATE (certainly *not* gas state or liquid state)... Also there are a number of variations that handle RF very well with low VSWR, and some have response times under a millisecond.
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Well, obviously. Solid state generally means made of semi-conducting material and containing no moving parts. Are you thinking of magnetic (coil) relays? The ones I'm using involve a LED and a MOSFET, not a coil.
http://www.cel.com/pdf/datasheets/ps7141a.pdf

These have an average response time of about .35ms. Also, I'm not running an RF signal through them. They are being affected by a nearby RF source.
Thanks, Dave
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David Harper wrote:

I *do* know the difference, and that the terminology "solid state relay" is used for relays using some kind of semiconductor technology - starting from incandescent lamp used to illuminate a CdSe or similar cell. With sufficent RF field, all "solid state relays" will be affected - ie: act as if some non-zero input had been applied. Sometimes, the RF field can even make the "solid state relay" act as if it were linear and/or erratic. In the case of LED/FET combo, the FET is the first to be affected. Proper shielding and RF bypassing will help reduce the effect. If the RF field is very strong, then the FET and perhaps the LED would be destroyed. Depending on the severity of the problem, one could go back to the older "solid state relay" technology and use the lamp/CdSe scheme OR use "iron state" relays (to coin a term), which can be rather sensitive.
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Thanks for answering my question - although on another part of the thread...
You may not know it, but the light from the LED does not directly turn-on the MOSFET. It shines on a string of small photovoltaic cells that charge the gates. When the light is off, the photocell leakage current (sometimes with an extra resistor across them) discharges the gate again.
Any idea what happens if an RF voltage is capacitively coupled from LED pins to the _string_ of photodiodes? It's called rectification. The resulting voltage turns on the gate.
Did you alrady do the test with the 1nF between driver size and output side?
Regards, Arie de Muynck
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Which pins are you suggesting I apply it across? Input ground to output ground?
Dave
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"David Harper" ...

side?
ground?
Yes. The basic idea is to minimize the RF voltage occurring across the isolation barrier by shorting it with the cap. Input GND to output GND is best, to other points it might cause other EMC problems.
It _may_ help to also put a ceramic 1nF cap across the output. This lowers the RF voltage across the FETs, half of which would be present at the output side of the isolation barrier. But it will decrease the output impedance, so it's a second choice solution only.
Regards, Arie de Muynck
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On 27 Jul 2004 09:07:30 -0700, snipped-for-privacy@gmail.com (David Harper) wrote:

I think he meant to the common terminal (pin5), from various places in the circuit, including possibly an input drive rail.
RL
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Robert Baer wrote:

From www.m-w.com:
Main Entry: solid-state Function: adjective 1 : relating to the properties, structure, or reactivity of solid material; especially : relating to the arrangement or behavior of ions, molecules, nucleons, electrons, and holes in the crystals of a substance (as a semiconductor) or to the effect of crystal imperfections on the properties of a solid substance <solid-state physics> 2 a : utilizing the electric, magnetic, or optical properties of solid materials <solid-state circuitry> b : using semiconductor devices rather than electron tubes <a solid-state stereo system>
So no, the molecular make-up of a device does not necessarily categorize it as solid-state. It's solid state if every atom in the device is relatively stationary, meaning no moving parts (e.g semiconductors).
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"Chris S." wrote:

Let us see - - the definition you quoted maid no mention, even indirectly concerning *moving* parts. And the last time i looked, each (individual) piece of copper , iron, plastic, glass, whatever does not move... And the combination of the copper and iron uses the magnetic properties of (solid) iron; which fits the quote exactly... BTW, iron has a rather definitive crystalline structure, and since annealed OHFC is not used for the coil, then the copper also has a crystalline structure.
Mind you, i am not arguing. Just point out a few iregularities...
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Robert Baser wrote:

True, although it does mention semiconductors, and I can count the number of semiconductors composed of moving parts on zero hands.

When used in solid-state electronics, correct.

...to move mechanical components in an electro-mechanical device.

Could have fooled me ;)

Well sure, if you want to get technical, vacuum tubes and semiconductors are both "solid" objects in the sense that they're not made out of gas, water, or plasma. But if you're going to nitpick subtle nuances of the English language there are far easier targets (why do we drive on a parkway and park on a driveway?).
I think the confusion concerns the use of "solid", which is used in the sense of the device's physical configuration, not so much its molecular state. We could use the term "finite-state", but that's generally used to describe electric circuits.
I'm just pointing out convention. In all fairness, the term is still jargon, but referring to any electro-mechanical device as "solid-state" will confuse most people.
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and EMI', on Mon, 26 Jul 2004:

Not any more. Consider the TI micro-mirror-matrix chips, for example, and solid-state microphones are appearing on the market, too.
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Regards, John Woodgate, OOO - Own Opinions Only.
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On Mon, 26 Jul 2004 11:28:08 +0100, the renowned John Woodgate

Solid-state accelerometers with on-chip bending arms have been available for about a decade- and have sold in large quantity.
Best regards, Spehro Pefhany
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Spehro Pefhany wrote:

I wouldn't necessarily classify MEMS devices as solid-state. While certain types make use of "bending" to move small actuators, they still rely on this movement to perform their function. The characteristic I typically associate with solid-state is a lack of dependence on physical motion to function.
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On Mon, 26 Jul 2004 07:28:28 -0400, the renowned "Chris S."

IMHO, the key characteristic is that the function depends on semiconductors. The branch of science involved is solid-state physics.
Best regards, Spehro Pefhany
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Tubes move electrons to function, semiconductors move holes to function :-).
Tim.
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about 'Solid State Relays

That's more of a technicality. Those microphones use piezo-electric effects, which is a function of [micro]strain.
Yes, technically the elements are moving a few microns (or less). There's several "solid state" temperature sensors that experience far more "movement" from thermal expansion than those microphones do.
They are not moving fractions of an inch (or more), like they are in electro-mechanical devices.
Dave
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"Chris S." wrote:

I was having a little fun...
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I think you're missing the original point. In the field of computer/electrical engineers, "solid state" refers to a branch of electronics based primarily on semi-conducting (ex. silicon) materials.
The whole "movement" part is really a minor footnote.
Your original statement about them being "solid" and not "gas" or "liquids" was obvious, and came from left field. I don't think anyone reading this thread would go into Radio Shack and ask for "liquid relays".
Dave
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On 26 Jul 2004 08:37:41 -0700, snipped-for-privacy@gmail.com (David Harper) wrote:
[snip]

Burridge might ;-)
...Jim Thompson
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