SSR Problem.

I think it would help us help you if you could post a circuit diagram on the web somewhere.

Messing with mains voltage is dangerous and you don't mention using an opto isolator.

Colin

a

much

into.

isn't

deicde

SSR.

9volt : battery across the drive lines. : Wiring: : I have, quite literally, an electrical cord that I spliced the SSR into. : One side of the cut is on pin 1, the other side is on pin 2 (which are : labeled 120/240vac). : Observations: : Whenever the cord is plugged in I read 124v at the plugged. There isn't : enough current to drive anything, but there is energy. This concerns me. : : Tests/Result: : LPT: First test was totally dead. : LPT: Second test I plugged in a light bulb, worked perfect for many : cycles. : LPT: OK, I hooked up my heating coil... dead. : 9V Batt.: Back to the light bulb... works (here I'm pretty frustrated) : LPT: Hook it back up to my heating coil... Works!!! : LPT: Do some tuning on my code that drives the device, run it again... : Works intermittently, once turned off it wouldn't always come back on. : : Dismantle, hook drive lines directly to 9 volts... Dead : Never works again. : : Can anyone see what I'm missing? I have similar designs running on 3amp SSR. : Is it possible that I have a bad SSR. : : Here is the spec sheet for the SSR: : :

Sounds like you blew out your printer port. 15ma would be the upper limit of it's operation, and I would not trust it to deliver that much current. A 74LS07 buffer with a separate 5 volt source from the printer port to the SSR would assure valid turn on/ off signal levels.

I have not worked with this specific SSR but I can give some general advice related to SSRs.

A small leakeage like this through SSR is quite typical. Theare are various technical reasons (leake through the conducting triac / SCR pair inside SSR, leakage caused by snubber network in SSR, possibly current taken by zero voltage swithing logic etc.)

Some leakage is a feature of SSR that you need to live with.

Possible reasons could be that you have bad SSR, you have used it improperly or your parallel port does not give enough current to reliably control the SSR (quite propable reason).

I read the datasheet briefly. It said "leakage current max 5 mA rms at 240V rms". So there can be quite considerable leakage and relay still OK.

The input parameters says for DC control models: " 3-32V DC on zero V turn on models, 3.5-26V DC on Random T turn on models" " Current 15 mA @ 5V DC max." The data sheet does no list the miminum needed current.

One test to check if the control from pralel port is enopugh for SSR: Wire the SSR to paralel port. Turn it on through software. Measure the voltage on the SSR input connectors. Check that the voltage there is within the input voltage limits of the SSR you use. If the volrage is below minimum listed voltage, then the parallel port does not give enough drive power to reliably operate the SSR.

I reply to both newsgroup and mail.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/

or use an opto isolator to provide both current gain and safety?

But, as a test condition I took the computer out the the equation. Shouldn't placing 9v directly on the drivers demonstrate that there is a problem with the SSR?

The whole computer element of the design can be ignored for now. My tests fail consistently either way.

-Brad

at a

much

into.

isn't

frustrated)

again...

deicde

SSR.

models"

Shouldn't the SSR itself be providing the necessary isolation?

"B. Woods" wrote

: But, as a test condition I took the computer out of the equation. Shouldn't : placing 9v directly on the drivers demonstrate that there is a problem with : the SSR?

Yes. If placing +9V from a battery on the input does not turn the SSR on with a load attached then you have a bad SSR.

NOTE: Operation without a load attached is not a valid test!

ALSO: if the battery is a typical portable radio type, it will go down quickly. A 6 Volt lantern cell would be better for testing since it is rated for higher current and will not drop in voltage while your testing.

: The whole computer element of the design can be ignored for now. My tests : fail consistently either way. : : -Brad :

"CWatters" wrote : "Roger Gt" wrote

: > Sounds like you blew out your printer port. 15ma would be the : > upper limit of it's operation, and I would not trust it to deliver : > that much current. A 74LS07 buffer with a separate 5 volt source : > from the printer port to the SSR would assure valid turn on/ off : > signal levels. : : or use an opto isolator to provide both current gain and safety?

The input IS via an optocoupler. That is what a SSR is! Even the 1 Amp units for 140VAC max have a 1KV isolation.

Yes it does...

Yip... Bad SSR.

I took it back and they replaced it. All is well now.

I knew my design was right. Thanks for the responses.

-Brad

Sounds quite low for maisn powered operated device to me... I woule like to see at least 2 kV isolation between input and controller load to be able to safely control AC currents (230V AC or 120V AC).

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/

"Tomi Holger Engdahl" wrote : "Roger Gt" writes: : > "CWatters" wrote : > : "Roger Gt" wrote

: > Input IS via an optocoupler. That is what a SSR is! : > Even the 1 Amp units for 140VAC max have a 1KV isolation. : : Sounds quite low for mains powered operated device to me... : I would like to see at least 2 kV isolation between input : and controller load to be able to safely control AC currents : (230V AC or 120V AC).

Then I would suggest that you do not buy THAT part! For 120VAC it will do, however what the guy is using has a much higher rating and a higher current. I use the little SIP SSR for controlling 24VAC valves in an irrigation system. The 1 KV isolation along with the Surgister at 400VAC is ample to pass UL (Did that on the first submittal.)