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Battery Powered Labby, Mark II

brianpe

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A while ago I built a battery powered lab laser (Battery Powered Labby). It was a fun project but beam quality wasn't that good and I there were some changes I wanted to make to the control electronics.

Meet Labby 2:

Changes from Labby 1:

  • Extra 2X cylindrical lens mounted back to back with 6X. Hugely improves beam shape.
  • Cylindrical lenses mounted on custom 3D printed mounts.
  • Larger heat sinks for better run time.
  • Much safer electronics. Impossible to turn key switch on and find laser was left 'on'.
  • Battery built-in, built in charger.
  • Temperature monitoring of diodes, with bar graph on front display.
  • Display can show percentage, amps going to diodes, or estimated output power.
  • Smarter diode selection, so lower powers only use one diode. Selectable selection modes including a "maximize runtime" mode that runs one diode at a time and chooses the coolest diode every few seconds.
The extra cylindrical lens (courtesy of This Post from Milos) makes a huge difference. The spot is a crisp square about .25" on a side after 20'. Just in case I also added threads for a SanWu 3x beam expander. By the way, SanWu says the threads on their beam expander are 11.4mm x .5mm. They aren't lying, but a tap for that seems impossible to find. I ended up drilling an 11mm hole, soft tapping it with a 11mm tap, and then forcing the stainless shaft of the expander in to make threads in aluminum. I'm not proud of it, but it screws on nice. With the expander mounted I can focus down to about 1/8", which is a tiny space to stuff 12 watts of photons. It burned through four layers of corrugated cardboard from 20' away without the expander on it, so I don't know if I'll use it often.

Thanks all to the great feedback from my first labby - I used a lot of it when designing this laser.

Labby 2 runs for about 3 minutes on full power before it gives a max temperature warning and takes about 2.5 minutes to completely cool back down. It always starts at 0% with the fire switch off when you turn on the key so there are no surprises. It still runs each NUBM44 at 5.5 amps, which is a little more than they want, but I rarely turn it all the way up. It uses a 8000mah RC car LiPo battery (Amazon link here) and can recharge it at four amps, so it doesn't take too long to fill it up when empty. It does not, however, fit in my pocket.

Edit: I was lacking describing the electronics, so here's an update (I've also attached the schematic to the gallery):

Power to everything is controlled by a 100A mosfet. This way the key switch doesn't have to handle the current to the laser drivers, and also allows me to power up the board when the charger is attached. I'm using an Adafruit Pro Trinket for processing and maxed out all the IO lines on the processor. It knows when the charger is attached, temps to both diodes, PWM control to both diodes, drives the display through I2C and has inputs for the encoder and fire buttons. PWM and power is sent to dual BlackBuck8 drivers preset to a max of 5.5A.

Pressing in on the encoder enables a menu mode where you can choose the display style (%, amperage to diodes or calculated power output) and diode settings (auto - drive one diode till we hit 40% power, then start driving both, each laser independently, both lasers, or run whichever laser has the lowest temp).

I grabbed temperature data off the NTM sensors on the diodes with my last labby but had to actually cut the pins to the processor because it was preventing laser startup. This turns out to be because the processors analog inputs have a 10k impedance, and was causing the BlackBuck to think the lasers were over temp. I now buffer the NTM voltage through op amps.

The display is 3V logic, so I chose a 3V processor. The PWM inputs to the BlackBuck require 5V, however, so there is a level shifter to shift the signal up to 5V. I'm not terribly happy with this. First, when then CPU is resetting the outputs are all high impedance which the level shifter interprets as a "high". Result: Reboot the processor and both lasers turn on. Bad. I worked around this by controlling the enable pin of the 5V regulator by the processor so I don't even enable outputs until I'm ready. But there is also some low voltage noise on the outputs. It's small, and would never be seen as a "1" to logic, but the BlackBucks do see this is an analog signal. The result is that even at 0% power, as long as that 5V regulator is enabled the lasers have a small amount of glow (way below threshold). I didn't notice this till very late -- it's totally invisible when you're wearing goggles. I worked around this in software. I only enable 5V when the laser is firing.

LiPo charging is handled through a Linear 4002 LiPo charging IC. I originally chose a different IC but I bit off more than my newbie SMD skills could handle. Here's the original chip:


The 4002 requires an external mosfet but was a slightly better form factor for me. I added a good copper pour to heat sink the mosfet and used an external heat sink glued to it since my prototype melted its solder joints! So far it has been working fine but it's a constant worry for me. The mosfet does get hot. It's switching at 500Khz.

BEAM SHOT:



Oodles of photos here:

 
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ElectricPlasma

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Cool! Looks very well built, definitely an improvement to the original. I would've liked to see more explanation on the electronics side, especially the interface, but I'm not complaining.

Other members have had problems with the Sanwu beam expander threads in the past as well. It appears they use either their own thread measurements or at least a very uncommon one. Unfortunately like you said buying a tap is difficult to find/very expensive so sometimes you just have to macgyver your own solution.

How do you find the 8Ah battery? Didn't see much of it in your write-up.
 

RedCowboy

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Rich " Lifetime17 " had a tap made. He can make a threaded adaptor to your liking, has made several for me.

fullsizeoutput_b5c.jpeg
 
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brianpe

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Cool! Looks very well built, definitely an improvement to the original. I would've liked to see more explanation on the electronics side, especially the interface, but I'm not complaining.

Other members have had problems with the Sanwu beam expander threads in the past as well. It appears they use either their own thread measurements or at least a very uncommon one. Unfortunately like you said buying a tap is difficult to find/very expensive so sometimes you just have to macgyver your own solution.

How do you find the 8Ah battery? Didn't see much of it in your write-up.
The 8Ah battery is an RC car battery I bought off Amazon. I've updated a post to include a link. Also, thanks for pointing out my lack of electronics description. I spent a lot of time and money on the electronics part and didn't want to get too wrapped up in it. But since there's interest....I've updated the post. Hopefully it's informative for folks.
 

reloader45

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Hello,

is it possible to cut an M11*0,5mm tread on the sanwu beam Expander? (is there enough material for a down size?)

I orderd a beam Expander yesterday and i have the 11*0,5 mm cutter in my Hobby room.

I do not like this Special threads. I also noticed, that the DTR copper moduls in 20 mm have a 17,83mm * 0,5mm thread, very Special.


best regards

Edgar
 

brianpe

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Dec 26, 2012
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Hello,

is it possible to cut an M11*0,5mm tread on the sanwu beam Expander? (is there enough material for a down size?)

I orderd a beam Expander yesterday and i have the 11*0,5 mm cutter in my Hobby room.

I do not like this Special threads. I also noticed, that the DTR copper moduls in 20 mm have a 17,83mm * 0,5mm thread, very Special.


best regards

Edgar
There is a decent amount of material thickness on the threaded part so you may have some luck re-threading it. If I were to try this I think I'd turn down a rod to exactly match the inside diameter before trying to turn down the barrel to the right diameter for an 11mm thread. That will hopefully prevent the wall from collapsing. Chucking it up in a lathe might be tricky without damaging the threads on the other end of it though, unless you can build a threaded adapter for that side (which I'm sure is also a a special thread).
 

reloader45

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Hello,

i will see what to do, when the beam expander arrives. Maybe it is easier to modify my homemade heatsinks to 11,4*0,5 mm. With the wright tap, it would be the way to go.
On the other side, it is easy to make an outside thread with the lathe. And going from 11,4 mm to 11,0 mm is only a short trip.


best regards

Edgar
 

BowtieGuy

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Hello,

is it possible to cut an M11*0,5mm tread on the sanwu beam Expander? (is there enough material for a down size?)

I orderd a beam Expander yesterday and i have the 11*0,5 mm cutter in my Hobby room.

I do not like this Special threads. I also noticed, that the DTR copper moduls in 20 mm have a 17,83mm * 0,5mm thread, very Special.


best regards

Edgar

Regarding DTR's 20mm modules, they are most likely an 18mm x 0.5mm thread; the OD of a threaded part is most always smaller than the nominal size (20mm), a size for size fit would be very tight, and the threads would be sharp and nasty looking.

The 0.17 smaller size is a bit much for such a fine pitch though.
 

reloader45

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Hello,
sorry, I checked the DTR modul again. The tread is between 16,83 mm and 16,9 mm. So it will be a 17*0,5 mm thread. That is not so exotic.


best regards

Edgar
 

CDBEAM777

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This is beautiful !!!! That is my FIRST comment !!!

So.....An order of magnitude more advanced compared to my Purple pHaze build....but...in the same neighborhood !!….errr…..well....in the same City !! hahaha !!

Such detail to permissive logic....WOW !!!........SO clean.....Nice lines....Optics are over the top !!!

FINALLY......SOMETHING .....I am going to copy( Steal ) the design !!!!

I have been looking for a " Three Stage switch "....Mini in size....BUT....with a sequence of ;

" All Power Off====> Power On to the system====> Laser On. All I can find are these
big-honk'in switches !!! ( As the switch used on the Purple pHaze )......but nothing small !!!.

There may be a latching switch that does this ??? Dunno....But....just a small mini toggle would do !!!

Anyway......Thanx for sharing !!! A very impressive build indeed !!!!!!!

CDBEAM

Addendum 1......Have been working with BP on a special switch.... Well...He is doing ALL the work....I am just cheering him on !!! He is an electronic Wiz !!! He is very, very good to work with !!! IMNSHO....a very small switch....as described above could and should find it's way into our more advanced builds !!!!!!!!!!!!!! Also...... maybe find a home into ANY build ???????????????....THANX BP

Addendum 2.... Someday....in the future.....When DEW ARE "Man Portable"....They WILL be equipped with various Systems Arrayal / Status Displays.....here to for called...... " SAD "...…....I have no doubt !!!!....Our humble baby steps are but a first attempt at this eventual deployment …..( I am sure the dArpa boyz are laughing now.....well....remember....WE do not have $ 500 to spend on a bolt !!!!! BUZZ OFF !! )....Someday....the " Black SUV " may be at my front door !!! Yikes !!!....OR.....Someday....a " dArpa Boy " may tell me to Buzz Off on this forum.... ????? MMMMM...Could Be !!
 
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