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Date: 05 Dec 2006 16:32:34
From: Robert Harmon
Subject: Picked up wrong Watlow 935A.
I wasn't paying close enough attention & bid on a PID that isn't compatable
with SSRs.

I have: 935A-1CD0-000R
If I'm reading Watlow's spec sheet correctly this is for an elctro-
mechanical relay.

I need: 935A-1CK0-000R
If I'm reading Watlow's spec sheet correctly this is for a solid state
relay (SSR).

Just out of curiosity, is there any way to convert one to the other?
There's a lot of the first type avaliable on eBay & so few of the latter
that it would likely be worth the effort.

Robert (If it weren't for mistakes I'd nearly be perfect.) Harmon
--
http://tinyurl.com/pou2y
http://tinyurl.com/fkd6r
Remove "Z" to reply via email.




 
Date: 06 Dec 2006 05:12:00
From: jggall01
Subject: Re: Picked up wrong Watlow 935A.

Johnny wrote:

> so does the 0.1 sec minimum cycle time apply to OT1 once OT2 is disabled?

Yes - a cycle time of 0.1 second is allowed on the 935A, although I
usually use 1 second. Shorter cycle times can produce an unpleasant
strobe effect if you have to put your espresso machine on a common
circuit with lights.

Jim



 
Date: 05 Dec 2006 17:31:51
From: jggall01
Subject: Re: Picked up wrong Watlow 935A.
Eric Svendson wrote:

> Chalk this one up to experience unless you hear from someone more intimately
> familiar with Watlow's internals - Jim? Jim? Jim?
>

Hi, Eric -

He clearly is undeserving ;-} but Robert is actually in good shape
with this controller.

All I can do is hold my hands a little differently and restate the
absolutely correct advice that Adam posted earlier.

The 935's all have a DC pulse output on OT1. This is a 5VDC logic
signal that is adequate for triggering most SSR's. The second output
is really irrelevant for this application (although it could be useful
for some steam temp control applications if configured correctly). I
advised Robert in a PM to disable OT2 through software, and wire the
leads from OT1 to terminals 3 and 4 on his SSR. Should work like a
charm.

Jim



  
Date: 05 Dec 2006 21:49:11
From: Johnny
Subject: Re: Picked up wrong Watlow 935A.

"jggall01" <jggall01@yahoo.com > wrote in message
news:1165368710.950058.320020@l12g2000cwl.googlegroups.com...
> Eric Svendson wrote:
>
> > Chalk this one up to experience unless you hear from someone more
intimately
> > familiar with Watlow's internals - Jim? Jim? Jim?
> >
>
> Hi, Eric -
>
> He clearly is undeserving ;-} but Robert is actually in good shape
> with this controller.
>
> All I can do is hold my hands a little differently and restate the
> absolutely correct advice that Adam posted earlier.
>
> The 935's all have a DC pulse output on OT1. This is a 5VDC logic
> signal that is adequate for triggering most SSR's. The second output
> is really irrelevant for this application (although it could be useful
> for some steam temp control applications if configured correctly). I
> advised Robert in a PM to disable OT2 through software, and wire the
> leads from OT1 to terminals 3 and 4 on his SSR. Should work like a
> charm.
>
> Jim
>
Hi Jim,

so does the 0.1 sec minimum cycle time apply to OT1 once OT2 is disabled?






  
Date: 06 Dec 2006 03:31:12
From: Robert Harmon
Subject: Re: Picked up wrong Watlow 935A.
"jggall01" <jggall01@yahoo.com > wrote in
news:1165368710.950058.320020@l12g2000cwl.googlegroups.com:

> Eric Svendson wrote:
>
>> Chalk this one up to experience unless you hear from someone more
>> intimately familiar with Watlow's internals - Jim? Jim? Jim?
>>
>
> Hi, Eric -
>
> He clearly is undeserving ;-} but Robert is actually in good shape
> with this controller.
>
> All I can do is hold my hands a little differently and restate the
> absolutely correct advice that Adam posted earlier.
>
> The 935's all have a DC pulse output on OT1. This is a 5VDC logic
> signal that is adequate for triggering most SSR's. The second output
> is really irrelevant for this application (although it could be useful
> for some steam temp control applications if configured correctly). I
> advised Robert in a PM to disable OT2 through software, and wire the
> leads from OT1 to terminals 3 and 4 on his SSR. Should work like a
> charm.
>
> Jim
>

Thanks for everyone's help. I'll pay closer attention to how I throw my
money around in the future.

Robert (Undeserving, but loveable..) Harmon
--
http://tinyurl.com/pou2y
http://tinyurl.com/fkd6r
Remove "Z" to reply via email.


 
Date: 05 Dec 2006 20:10:18
From: Eric Svendson
Subject: Re: Picked up wrong Watlow 935A.
Unfortunately, I believe you have "bought the farm." The mechanical relay
on PID controllers is just that, a relay. It is a switch (usually n/o) to
be wired into an already powered circuit. While I suppose you could rig
this up with a 9V battery (maybe that's enough, maybe) to trigger the SSR -
it just doesn't sound too right to me.

Not only that but now you would be sacrificing all the attributes of a fast
cycle SSR.

Chalk this one up to experience unless you hear from someone more intimately
familiar with Watlow's internals - Jim? Jim? Jim?

Eric S.



"Robert Harmon" <r_h_harmon@Zhotmail.com > wrote in message
news:Xns98906B4135F2ErhharmonZhotmailcom@207.217.125.201...
>I wasn't paying close enough attention & bid on a PID that isn't compatable
> with SSRs.
>
> I have: 935A-1CD0-000R
> If I'm reading Watlow's spec sheet correctly this is for an elctro-
> mechanical relay.
>
> I need: 935A-1CK0-000R
> If I'm reading Watlow's spec sheet correctly this is for a solid state
> relay (SSR).
>
> Just out of curiosity, is there any way to convert one to the other?
> There's a lot of the first type avaliable on eBay & so few of the latter
> that it would likely be worth the effort.
>
> Robert (If it weren't for mistakes I'd nearly be perfect.) Harmon
> --
> http://tinyurl.com/pou2y
> http://tinyurl.com/fkd6r
> Remove "Z" to reply via email.




 
Date: 05 Dec 2006 14:45:45
From: Johnny
Subject: Re: Picked up wrong Watlow 935A.

"Robert Harmon" <r_h_harmon@Zhotmail.com > wrote in message
news:Xns98906B4135F2ErhharmonZhotmailcom@207.217.125.201...
> I wasn't paying close enough attention & bid on a PID that isn't
compatable
> with SSRs.
>
> I have: 935A-1CD0-000R
> If I'm reading Watlow's spec sheet correctly this is for an elctro-
> mechanical relay.
>
> I need: 935A-1CK0-000R
> If I'm reading Watlow's spec sheet correctly this is for a solid state
> relay (SSR).
>
> Just out of curiosity, is there any way to convert one to the other?
> There's a lot of the first type avaliable on eBay & so few of the latter
> that it would likely be worth the effort.
>
How about the 9V battery solution used here:
http://groups.google.com/group/alt.coffee/browse_thread/thread/df2df372385f3
545/5c642080ac95a68e

although I believe the min cycle time on the relay version is more than the
SSR version




 
Date: 05 Dec 2006 10:57:43
From: Adam Tenenbaum
Subject: Re: Picked up wrong Watlow 935A.
Robert Harmon wrote:
> I wasn't paying close enough attention & bid on a PID that isn't compatable
> with SSRs.
>
> I have: 935A-1CD0-000R
> If I'm reading Watlow's spec sheet correctly this is for an elctro-
> mechanical relay.
>
> I need: 935A-1CK0-000R
> If I'm reading Watlow's spec sheet correctly this is for a solid state
> relay (SSR).
>
> Just out of curiosity, is there any way to convert one to the other?
> There's a lot of the first type avaliable on eBay & so few of the latter
> that it would likely be worth the effort.
>
> Robert (If it weren't for mistakes I'd nearly be perfect.) Harmon

Robert - what type of application were you going to use the PID
controller for? In particular, did you _really_ need the second
output? A single-boiler machine like a Silvia/Gaggia draws somewhere
in the ballpark of 7-10A of current (on a 110/120V circuit), which is
much higher than the ratings of either the mechanical relay / SSR.

The "typical" way to use these controllers is by using the DC
logic-level output from "Output 1", which both of these controllers
have (indicated by the "-1C" in the part numbers). This low current
output is used as an on/off switch for the DC side of an external SSR -
just find one rated for 20-40 A, and you're good to go!

Adam (Long time lurker, first time poster)



 
Date: 05 Dec 2006 10:47:15
From:
Subject: Re: Picked up wrong Watlow 935A.

mandtprice@gmail.com wrote:
> A mechanical relay is stronger, but slower than a solid state one and
> the specs sheet confirms that intention on the designers part. The
> specs list an SSR at .5A and 24-240 vac while the mechanical relay is
> 2A at /only/ 240 vac. You /should/ be able to hook up the mechanical
> part to an SSR, but not the other way around.

replying to and disagreeing with my previous post:

Looking at the spec sheet closer, the mechanical relay option is preset
to a 30s cycle time with a 5s minimum, versus .1s for the TTL and SSR
options. If this is for an espresso machine, that probably won't be
fast enough to keep up with incoming cold water during a shot. I think
you are out of luck.

Matthew



 
Date: 05 Dec 2006 10:25:03
From:
Subject: Re: Picked up wrong Watlow 935A.
Robert Harmon wrote:
> I wasn't paying close enough attention & bid on a PID that isn't compatable
> with SSRs.
>
> I have: 935A-1CD0-000R
> If I'm reading Watlow's spec sheet correctly this is for an elctro-
> mechanical relay.
>
> I need: 935A-1CK0-000R
> If I'm reading Watlow's spec sheet correctly this is for a solid state
> relay (SSR).
>
> Just out of curiosity, is there any way to convert one to the other?
> There's a lot of the first type avaliable on eBay & so few of the latter
> that it would likely be worth the effort.

A mechanical relay is stronger, but slower than a solid state one and
the specs sheet confirms that intention on the designers part. The
specs list an SSR at .5A and 24-240 vac while the mechanical relay is
2A at /only/ 240 vac. You /should/ be able to hook up the mechanical
part to an SSR, but not the other way around.

The only downside is that the controller may be preset to drive the
output at a longer cycle time, which you will want to shorten for an
SSR. A mechanical relay wouldn't take the fast switching abuse that an
SSR will. You should be fine; the worst that could happen is that it
won't work, but it won't break anything.

Matthew