Thermal control question

[Sam Goldwasser]

Here are some pictures of the proposed design. I bought the mirror mount
but will machine the LBO mounting fixture.

http://oregonstate.edu/~wolcottr/Laser_files/Yag pictures Control Laser 511/Doubling setup/

You should probably put just the inner LBO mount on a TEC.

P.S. What CAD program are you using?

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[Robert Wolcott]

The CAD program is Solidworks and it is very easy. Designing the mount
probably took about four hours because there was design work involved.
Disassembling and modeling the mirror mount only took about 2 hours because
I was just measuring parts. I think it is extremely useful and worth the
time.

I have heard that LBO is hydroscopic, is this true? Do you know if the
mount will need to seal it from the atmosphere? That is a reason that the
mount is designed the way it is. If it does not need to be sealed I will
simply cut of the left half of the pink piece and merge the rest of it with
the yellow piece, allowing plenty of room for the TEC wires and heat sink.

The current setup allows for five DOF adjustment (3 axis on the LBO mount,
X-Y translation of the lens on its mount). I plan to use the lens
adjustment to aim the beam at the crystal. It should be very precise.

 

[Robert Wolcott]

Thanks for the reply. I'm sure a PID is overkill for this but at $30 one
can't go wrong. For that price I get a digital display with all kinds of
bells and whistles and a unit that works like clockwork. I also like being
able to set the temperature where I like it and then just forget about it.
If it weren't for Ebay I wouldn't even consider a PID for this. Not at
retail price

Bob

 

[Sam Goldwasser]

The CAD program is Solidworks and it is very easy. Designing the mount
probably took about four hours because there was design work involved.
Disassembling and modeling the mirror mount only took about 2 hours because
I was just measuring parts. I think it is extremely useful and worth the
time.

I have heard that LBO is hydroscopic, is this true? Do you know if the
mount will need to seal it from the atmosphere? That is a reason that the
mount is designed the way it is. If it does not need to be sealed I will
simply cut of the left half of the pink piece and merge the rest of it with
the yellow piece, allowing plenty of room for the TEC wires and heat sink.

Looking at various manufacturers of LBO, it seems to have "low hygroscopic"
sensitivity and should be handled in dry conditions. Definitely not as
robust as KTP. However, some say it (at least theirs) is "non-hygroscopic".
I'd err on the side of keeping it sealed.

Search on "LBO hygroscopic"

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| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

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Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
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[Jamie]

"Robert Wolcott" bravely wrote to "All" (14 Jan 05 21:47:29)
--- on the heady topic of "Thermal control question"

RW> From: "Robert Wolcott" <[email protected]>
RW> Xref: aeinews sci.electronics.repair:7183

RW> This is more of a design question, but there are some pretty sharp
RW> people on this board so I'll post it here. I am designing a closed
RW> loop thermal control unit that would like to be very accurate (+/- .2
RW> degrees C). I plan to use a PID controller with an RTD sensor and a
RW> small tape style heater.
RW> Most PID controllers only provide a signal out and do not directly
RW> power the heating element. If I had a PID controller providing a low
RW> voltage signal (mV), what sort of intermediate circuit would I need to
RW> power a 10-50 watt heating element? My main goal is not necessarily
RW> accuracy, but stability.
RW> Thanks,
RW> Bob

If it is AC power then you need to convert the PID voltage level into
a phase angle in order to control a TRIAC. This can be done brute
force with on/off control, slightly better by varying a pulse rate, or
precisely with a countdown circuit driven by a pll sync'd to the AC
phase. It depends on application.

A*s*i*m*o*v

... Power is obtained by current meeting resistance

its common place to simply use a solid state switch which is a triac in
side.
most heat controllers will give you a relay & logic out, all that is
needed is to turn on the solid-state switch via the logic level.