[TriEmbed] SSR sources: was Re: T-962 reflow oven notes

Glen Smith mrglenasmith at gmail.com
Wed Sep 24 19:33:36 CDT 2014


I have not played around much with them but I have noticed that they do
have problems turning OFF (like open circuit off) with low currents. I have
an Omron relay controlled by a low voltage key switch to control my rain
barrell pump. There is a neon indicator lamp that shows that the pump is
enabled. If I turn off the key switch while the pump is running, the
circuit turns off perfectly. If I turn off the key switch when the pressure
switch is off and thus the only current in the circuit is the neon lamp,
there is not enough current draw to clamp off the relay. This leaves my
circuit in an odd state of "sorta on". I "fixed" the problem by adding an
incandescent light bulb in parallel with the pump so there is always a
fairly good current draw.

Probably not an issue for what you are doing, but worth mentioning.

I have a number of Omron G3NA-220B 20A relays with a control voltage of
5-24vdc that I am willing to part with.

Glen
On Sep 24, 2014 7:48 PM, "Michael Fulbright" <mike.fulbright at pobox.com>
wrote:

> I'm going to hijack this thread slightly as I was about to ask this
> question and it is related to reflow ovens...
>
> I'm starting to build a reflow solution and I've been researching solid
> state relays.  There are some nice "brand name" relays on Digikey
> (Panasonic, Omron, etc), but then there are a bunch of low-end alternatives
> that are 1/3 the cost.  If you read reviews and look at other reflow
> projects on the web they seem to do OK - but since we're controlling main
> voltage I'm more than happy to spend more money for some insurance against
> a disaster.
>
> Could anyone comment on their personal experience with SSR devices?  I'm
> looking at 25A and 40A.
>
> For now I figured I'd mess around with a homegrown PID solution just so I
> could learn more about it.
>
> Thanks,
> Michael Fulbright
>
>
> On 9/24/2014 6:24 PM, Rick wrote:
>
>> Good evening all,
>>
>> Pete ... I'd suggest a nice 1/4" aluminum plate upon which you place your
>> PCBs. Your thermocouples can either be taped to your board (kapton is great
>> for this), or permanently fastened to the aluminum. You need some nice
>> thermal mass to reduce your setpoint oscillation.
>>
>> Does your PID controller have a training mode? If so, install the
>> aluminum with the thermocouples, train it, and then run a profile with an
>> external thermocouple not tied to the system watching as well.
>>
>> You probably want a HEPA filter on the exhaust port ... though I'd
>> provide some cooling in the form of an aluminum vent pipe before the filter
>> ... no need to get the filter hot. You can buy a large HEPA filter and cut
>> it down to make multiple small ones if you wish (the local home improvement
>> stores carry a few HEPA filters ... beats ordering and waiting for the boat
>> from overseas). You probably don't want to spend the money on an automotive
>> "cabin" filter ... very expensive for what it provides.
>>
>> Cooling the exhaust also helps condense the volatiles and helps reduce
>> the filter loading ('cause you can shake the filter off rather than replace
>> it every x hours).
>>
>> Hope this helps,
>>
>> Rick
>>
>>
>>
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>
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