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Tutorial: Blu-Ray With TEC! - Step by Step

jayrob

jayrob

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Thanks guys...

This one is a really good project! You'll like it... :cool:

I need to slap a 445 in there for testing...
 





Seoul_lasers

Seoul_lasers

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I am going to try to build my own version of this soon!
I am going to try it with a PC heatsink instead of the box.
 
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dnar

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Nice build Jayrob! I am planning a TEC block for my yet to arrive 200mW DPSS. I have a 33W TEC here, a bit overkill but it is the smallest I could buy at the time. I plan to drive it closed loop with an Arduino/H-Bridge running a PID loop.

I have concern over your choice of voltage regulators, and would like to raise the following negative factors surround them and your application:
  1. I did not see any capacitors in your build, these regs can oscillate like mad with out them.
  2. Linear regs drop regulation when (Vin -3V) < Vout.
  3. Linear regulators are NOT efficient, ergo waste battery energy.

For low voltage/battery applications I use switching regulators with typical efficiency of 85% or more.

These are nice (I use these) but not as cheap, checkout the efficiency curve in the following compared to the LM7805. Newark/Farnell carry many "78xx" drop-in replacements too.

5V 1A Switching Voltage Regulator - Robot Gear

These are also cool, good for prototyping: 3A (3-13V 25W) Step down adjustable switching regulator

Cheers and +1 rep for the build.

Wayne.
 
jayrob

jayrob

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I'm using FlexDrives, which have the components on them...

They just need anywhere between 2.5 volts and 5.5 volts supply. (ver. 3 FlexDrives)

Thanks for the rep!
 
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dnar

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Yeah cool, I understand, however your preceding linear regulators are wasting energy (lost as heat). This loss could be minimized using the switching equivalents.

Add to this, once the 7805 reaches drop-out (Vin = just under 8V) Vout will drop below 5V and losses increase. For these reasons, linear regs are a poor choice for battery applications.

Rep? No worries, I find your posts most informative. Cheers.
 
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seoguy

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dnar said:
For low voltage/battery applications I use switching regulators with typical efficiency of 85% or more.
Click to expand...

Wayne, are you aware of any devices like those you mentioned, but that instead of constant-voltage regulators, are constant-current?

Thanks!
 
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dnar

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seoguy said:
Wayne, are you aware of any devices like those you mentioned, but that instead of constant-voltage regulators, are constant-current?

Thanks!
Click to expand...
No. In fact, constant current sources typically need to be linear and lossy.

The best you can do to reduce inefficiencies with constant current sources is to
provide the current regulator with *just enough* voltage to provide the required current at the required load voltage.

ie. Any series pass current regulator driving an LD will be more efficient with an input of 6V compared to the same with 12V.

Simple ohms law. The same can be said for any series pass current regulator, including a resistor alone.

If you are concerned about battery life and/or current regulator heat dissipation then provide the minimal input voltage you can while maintaining current regulation with some headroom, and providing the regulator of choice it's required input range.
 
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seoguy

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OK, thanks anyway.

If you are concerned about battery life and/or current regulator heat dissipation then provide the minimal input voltage you can while maintaining current regulation with some headroom, and providing the regulator of choice it's required input range.
Click to expand...

Am aware of that. Unfortunately, with battery-operated devices (particularly those based on standard Li-ion rechargeables), we often don't have the fine-grained control over the input voltage to accomplish that. Otherwise, we would only be dealing with losses from the drop-out voltage of the linear regulator in question + a bit extra (headroom), and losses would be much less of a problem.
 
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dnar

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What is your battery supply when fully charged (laser on) and also at the threshold of unusable?
 
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dnar

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seoguy said:
Wayne, are you aware of any devices like those you mentioned, but that instead of constant-voltage regulators, are constant-current?

Thanks!
Click to expand...

While still linear series pass, this LED constant current driver looks to me as if it will also work as a LD regulator. It regulates down to around 1V output AND included a TTL enable line (321U model only).

I might grab a few and try them out. $0.62 each at Farnell for 1-24 units.

http://www.infineon.com/dgdl/bcr320...c04c4&fileId=db3a304324fc7f9a0125204353c942f9
 
jayrob

jayrob

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dnar said:
What is your battery supply when fully charged (laser on) and also at the threshold of unusable?
Click to expand...

Just in case that question was about this build...

I've got 2 X 1320mAh Li-Po packs in parallel...

So that means a total of about 2640mAh's capacity.

I would estimate that the entire build uses maybe 1300mA's or so. (fan, peltier, diode with FlexDrive, regulators, Lipo alarm)

So it should be at least 1 1/2 hours (possibly 2 hours) of operation before I need to charge the batteries...

I doubt that the Lipo alarm uses much, but it is nice, because the color of the light will change and let me know when the batteries need charging. :)

LiPo Alarm color code:

Bright blue - Full charge
Cyan - Very good
Green - Good
Yellow/Amber - Low warning
Red - Batteries low (70%)
 
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dnar

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Thats not too bad actually Jayrob.

And Li-Po are what, 2.7v flat to about 4.3v charged? Perfect for LD's by the looks.

Li-Po do scare me, I have a few in counter-rotating RC helicopters. They do have the capability of bursting in to flames if sensible usage/charge cycles are not observed.
 
ossumguywill

ossumguywill

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dnar said:
Thats not too bad actually Jayrob.

And Li-Po are what, 2.7v flat to about 4.3v charged? Perfect for LD's by the looks.

Li-Po do scare me, I have a few in counter-rotating RC helicopters. They do have the capability of bursting in to flames if sensible usage/charge cycles are not observed.
Click to expand...
that's why you always buy protected for flashlights or lasers. If you don't, be ready to lose your hands(or more likely your expensive gear).
 
jayrob

jayrob

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dnar said:
Thats not too bad actually Jayrob.

And Li-Po are what, 2.7v flat to about 4.3v charged? Perfect for LD's by the looks.

Li-Po do scare me, I have a few in counter-rotating RC helicopters. They do have the capability of bursting in to flames if sensible usage/charge cycles are not observed.
Click to expand...

That's why I have the Lipo alarm... Never let Lipo batteries get discharged to low. And then charge them with a quality balance charger...
 
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