Calibration Laser weekend project

[justinjja]

Going to be making my self a new calibration laser this weekend.

I'll be using a Tec, Controlled by a microcontroller, to regulate the temperature.

Diode with be an M140 running at about 1W.


Should be fun, I'll update this thread with my progress


EDIT:
Part list
1)6A, 5V PSU from industrial router
2)20W tec
3)Aixiz heatsink
4)M140 in aixiz module
5)Temp sensor module from broken radio (Thanks Autoitking)
6)Massive CPU Heatsink
7)Microcontroller
8)Linear driver w/ set resistors

Need to find some fets that will cooperate with my 3.3V microcontroller
May need to add a fan, not sure yet...

 

[Bionic-Badger]

Before you star, get rid of that shitty Aixiz module holder. They have huge air gaps around the module that will make that heatsink essentially worthless.

If you want something better, use one of those CNC shaft supports (like this or this), or some sort of tighter-fitting mount.

If you want a calibration laser you should also have a photodiode near the output (use a semi-reflecting piece of glass to tap off some of the power) so that you can provide direct feedback to the power and cooling circuitry. Otherwise you'll just be relying on the temperature to provide output stability, rather than directly controlling the output stability.

 

[justinjja]

Before you star, get rid of that shitty Aixiz module holder. They have huge air gaps around the module that will make that heatsink essentially worthless.

Ya aixiz didn't do a very good job with these heatsinks,
but I knew that going in,
I wont have any trouble keeping the diode cool,
even with nonideal thermal transfer...

If you want something better, use one of those CNC shaft supports (like this or this), or some sort of tighter-fitting mount.

Ill keep those in mind, they look good.
but I'm not waiting on something from china for this build,
IIRC its new years over there atm...

If you want a calibration laser you should also have a photodiode near the output (use a semi-reflecting piece of glass to tap off some of the power) so that you can provide direct feedback to the power and cooling circuitry. Otherwise you'll just be relying on the temperature to provide output stability, rather than directly controlling the output stability.

I've thought about this, but im not convinced it is a good idea.
adding a photodiode just adds another set of variables I have to try to control...

The only 3 things that effect a diodes output that I am aware of are
temp, current, and age.
I shouldn't have any trouble with temp,
And by putting the driver on the temp controlled heatsink,
there should be virtually no fluctuation in current.

That only leaves age,
by keeping the output within spec I will minimize the aging on the diode.
and a photodiode would probably age too...

 

[lasersbee]

Perhaps this will help...

A while ago we built a liquid cooling tower to keep
a 40Watt FAP Laser stable for testing Thermopile
coatings. We chose a 40Watt Laser to run it no more
than 20 Watts to make sure it had a long life..

We installed an aluminum water cooling block thermally
attached to the base of the FAP. That is then supplied
water circulated by a Pump.
The outflow of the FAP cooling block goes into a radiator
that has a 3 speed fan on it and then goes back into the
reservoir.

The TEC in the FAP Laser is manually current controlled
by the knob on the face of the tower and is monitored
on the LCD screen.

There is a temperature sensor on the Laser Module in
the FAP housing on one side of the TEC.
There is another temperature sensor on the Base of
the FAP housing on the other side of the TEC.
There is a 3rd temperature sensor on the Reservoir.
All those temperatures are monitored on the backlit
LCD screen.

There is an optical sensor on the Laser Module in the
FAP housing but it is not yet used.

The Laser Power holds quite steady with just small
manual adjustments of the TEC current control when
needed.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

 

[justinjja]

Perhaps this will help...

A while ago we built a liquid cooling tower to keep
a 40Watt FAP Laser stable for testing Thermopile
coatings. We chose a 40Watt Laser to run it no more
than 20 Watts to make sure it had a long life..

We installed an aluminum water cooling block thermally
attached to the base of the FAP. That is then supplied
water circulated by a Pump.
The outflow of the FAP cooling block goes into a radiator
that has a 3 speed fan on it and then goes back into the
reservoir.

The TEC in the FAP Laser is manually current controlled
by the knob on the face of the tower and is monitored
on the LCD screen.

There is a temperature sensor on the Laser Module in
the FAP housing on one side of the TEC.
There is another temperature sensor on the Base of
the FAP housing on the other side of the TEC.
There is a 3rd temperature sensor on the Reservoir.
All those temperatures are monitored on the backlit
LCD screen.

There is an optical sensor on the Laser Module in the
FAP housing but it is not yet used.

The Laser Power holds quite steady with just small
manual adjustments of the TEC current control when
needed.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

Very cool, (Literally lol)
Ive always wanted to do a water cooled Laser,
but never had a laser powerful enough to justify it

a few years ago I had a water cooled computer,
do they make water cooling equipment for lasers?
or did you repurpose some computer water cooling gear?
fun stuff

 

[lasersbee]

Very cool, (Literally lol)
Ive always wanted to do a water cooled Laser,
but never had a laser powerful enough to justify it

a few years ago I had a water cooled computer,
do they make water cooling equipment for lasers?
or did you repurpose some computer water cooling gear?
fun stuff

Thanks...
There are no Computer Cooling parts used. They seemed too
expensive and we approached it from a cost perspective.

The 15mm X 12mm X 3mm Radiator and 3 Spd cooling fan were
bought on eBay...
The Pump was a windshield washer type from a local car parts
supplier running at a 1/2 required voltage to increase it's life span.
The Cooling Block is thermally bonded to the bottom of the 40W FAP
came from an R/C parts supplier. It is used to cool Li-Po batteries.
The reservoir we built using 4" plastic drain pipe and some brass
fitting from the local hardware store.
The enclosure was a case from an old 486 Computer..

The micro-controller Firmware to keep a track of everything and
over/under temp safety lockouts we wrote and the electronics and
circuitry we did in house.

The cooling tower is PNP... We can easily disconnect and change
out the 40W FAP Laser for the other power types (30W..12W..etc)
we have in the shop in about 5-10 seconds.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

 

[justinjja]

Couple more pics:

Diode module with temp sensor sitting right on the diode:

Hot side HS, TEC, Coldside HS, and linear driver:

 

[Seoul_lasers]

Interesting idea. What are you measuring the laser output with?

a little point to clear up.
I expect you'll be adding a fan on the radiator?

 

[justinjja]

Interesting idea. What are you measuring the laser output with?

a little point to clear up.
I expect you'll be adding a fan on the radiator?

It will have a fan, but it shouldn't need one usually.
That heatsink should be able to passively dissipate 15W...
But in a warm room it may have to kick on.

 

[Things]

Why the stupidly oversized heatsink with a crappy alu mount that probably only contacts 10% of the module? I don't think this is going to be any where near as stable as you're aiming for. You're also probably going to have to go a completely different driver route if you want stability, including optical feedback. Sticking it on a TEC isn't going to make it stable at all.

 

[justinjja]

Your mixing up thermal transfer with satiability,
My diode could be sitting at 60c, and if it stays right at 60c, the diodes power output is going to be stable...

That's just an example,
Im planning on running it at 25c, but we will see.

And there is nothing stupid about the size of the heatsink...
I needed a heatsink that can dissipate 15w of heat passively
The fan will only be a backup, airflow from the fan could mess with LPM readings

 

[Things]

My diode could be sitting at 60c, and if it stays right at 60c, the diodes power output is going to be stable...

Without optical feedback, it won't be stable. There is much more to consider than just cooling the laser itself. Your driver becomes a bottleneck too, and I would put bets on a linear driver being nowhere near stable enough without active monitoring. If you are using this laser to calibrate a LPM, I would expect nothing short of both thermal and optical regulation. If i's just a stable laser for personal use, and not a product, then thermal regulation would be fine.

 

[justinjja]

Just finished running it for a few hours,
Diode temp settled about 3c below ambient.

To give my self a little wiggle room ill program my microcontroller to hold the diode at 30c

 

[robmobz]

. Your driver becomes a bottleneck too, and I would put bets on a linear driver being nowhere near stable enough without active monitoring.

I would think that a properly heatsinked linear would be stable enough for most purposes. For example the one in my build had, at 1.5A a 8mA drift over a 20 minute test or a 1mA drift on low mode (255mA).

All that has for cooling is a £2 TO-220 heatsink and a case fan mounted on the case pointed past it.

 

[Things]

Depends what you call "stable". By the word "calibration laser", it sounds like it might be used to calibrate LPMs, in which case even a few mW's of drift would be unacceptable. It's all quite subjective.

 

[robmobz]

Fair enough, it is just that it is stable enough for most jobs at that power in my experience. Never having tried to calibrate a LPM I don't know how much difference it makes but it is only around 1mA after it has warmed up in high power mode. I suppose it also depends on how accurate the sensor is how much difference it makes.