SSR Problem.

[B. Woods]

I'm completely frstrated with an SSR design I'm working on. I'm hoping
someone can tell me what I'm missing.

Facts:
I'm working with a Potter & Brumfield SSR-240D50.
I'm trying to switch a simple resistive heating coil that comes out at a
little over 4 amps at 124V.

Initially I had this hooked to a pin on my printer port. I have other, much
smaller, SSR's that I run this way. For some of my tests I put a 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.

(Step 10 - Hit the newsgroups at www.deja.com, find little of value, deicde
to post)

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:
http://www.steveneng.com/Tech_Support/PDFs/37SOLID.PDF

<Please respond to the newsgroup> bwoods114<at>charter(dot)<net>

Thanks,
Brad

 

[CWatters]

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

 

[Roger Gt]

: I'm completely frstrated with an SSR design I'm working on. I'm
hoping
: someone can tell me what I'm missing.
: Facts:
: I'm working with a Potter & Brumfield SSR-240D50.
: I'm trying to switch a simple resistive heating coil that
comes out at a
: little over 4 amps at 124V.
: Initially I had this hooked to a pin on my printer port. I have
other, much
: smaller, SSR's that I run this way. For some of my tests I put a
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:
: http://www.steveneng.com/Tech_Support/PDFs/37SOLID.PDF
:

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.

 

[Tomi Holger Engdahl]

I'm completely frstrated with an SSR design I'm working on. I'm hoping
someone can tell me what I'm missing.

Facts:
I'm working with a Potter & Brumfield SSR-240D50.

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

I'm trying to switch a simple resistive heating coil that comes out at a
little over 4 amps at 124V.

Initially I had this hooked to a pin on my printer port. I have other, much
smaller, SSR's that I run this way. For some of my tests I put a 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.

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.

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.

(Step 10 - Hit the newsgroups at www.deja.com, find little of value, deicde
to post)

Can anyone see what I'm missing? I have similar designs running on 3amp SSR.
Is it possible that I have a bad SSR.

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).

Here is the spec sheet for the SSR:
http://www.steveneng.com/Tech_Support/PDFs/37SOLID.PDF

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.

<Please respond to the newsgroup> bwoods114<at>charter(dot)<net>

I reply to both newsgroup and mail.

 

[CWatters]

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?

 

[B. Woods]

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

 

[Walter Harley]

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

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

 

[Roger Gt]

: 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
:

 

[Roger Gt]

: "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.

 

[B. Woods]

Yes it does...

 

[B. Woods]

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

 

[Tomi Holger Engdahl]

: "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.

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).

 

[Roger Gt]

: "Roger Gt" writes:
: > "CWatters" wrote
: > : "Roger Gt" wrote
<snip>
: > 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.)