PLTB AKA Portable Laser Test Bench (Work In Progress) LOTS-O-PICS

[Kmor2004]

After getting a few lasers, and a lot of thought I felt it was darn near time I got around to getting some of the more important devices to building lasers as a hobby, so I started a mental check list:

Test load? ...... Nope dang
LPM? ...... Nope Sh!t
Know adjustable driver from 1mA to 2A? ..... GAH I"m Screwed!

So I set forth into making the PLTB to include all of these aspects wit ha few extra bells whistles and lights.

Now that the back ground has been laid, I present to you the LPF community my WIP, We start with the Eagle Schematic and oard layout.

Thanks to some really smart and really board guy I was also able to make the 3D file of the board top and bottom mostly populated.

Once the board design was settled on it was sent off to Dork-bot (like how I used the dork bot color scheme for the 3D?

So I got the boards in with the exception of a few smudges on the silk screen, and not realizing a few things during board layout...such as how small some of the holes where gonna be, how close the diodes for the test load were to each other, the fact that the 328-pu NEEDs a 16MHz crystal to run the arduino code the way I wanted to run it..., some simplification factors for the selectors, and that fact that gnd for the 358 was not there, and a revision for the LPM portion that if the amplification hit 5V that I could use the remaining ADC channel to measure directly off the TEC.

Despite doing PCB's before I had ordered my parts 1st then I tested the layout to make sure parts fit, like I said with the exception of some forgetfulness, lack of insight, and improper size checks, I still ordered the boards, and populated one of them, I'll add the pic for the back side after I get most of the testing done wit hthe code, since I actualy have 2 parts of coding to do.

Now I'm to the testing part where it also includes working on a LOT of coding since I have to code my 4D systems 280 X 320 Color LCD with touchscreen, overboard you betcha, but I wasn't using it for any projects at the time and I thought it would make adjusting some of the settings a little cooler, and be able to display a graph, mostly because I like graphs!

Then some pics of the screen thats up right now for testing purposes, so I can see the raw data coming into the display, and a Pic of what I hope the graph capabilitys will look like with the option to set minimum laser power, and maximum lasing power either in raw data mode and have it shown on the graph.

BOOM BABY!!!!!!!:drool::drool::drool::drool:

 

[daguin]

I am not an electronics guy

But I LOVE the idea :gj:

Peace,
dave

 

[Trevor]

Nice!

I'm working on something very similar, but lack of a Flexmod P3 sort of stalled the whole thing.

-Trevor

 

[Kmor2004]

Heck you don't need a P3 If you notice my driver is just a PWM pin into an RC DAC that drives a 2A npn, Here's the graph for 3.7V, and the test laod set for Red LD's

I included a MS excel file made in open office portable, so you can see the information better.

 

[Trevor]

Have you scoped the DAC output to make sure it's not pulsing though?

-Trevor

 

[DTR]

Awesome. I like it.:beer:

 

[Kmor2004]

Yep, trevor I have a Hantek DSO 8050 which has a DMM 6000 count and a dual channel Oscope, and when I picked the values for the DAC and the frequency I knew the freq needed to be something like 3-5x at least but I think I'm I'm pushing 10x the minimum freq.

Since you asked and my rambling might be confusing, at 800 counts 50% duty cycle I'm getting a DAC voltage of 2.34 average and 2.35 RMS with a max voltage of 2.40 and minumim voltage of 2.34 and peak to peak voltage of 125mv or 12.5mV.

I should know better but I always get confused when using the Oscopes 1x and 10x functions I normally just leave my probes and the settings at 1x but to get those numbers I had to switch the probe to 10X since I ran out of range both in offset of the scope and measurement, I switched it from DC measurement to AC just to double check and at 1x probe and scope, scope at 20mV/per I'm getting ~100mVPP with 51.2mV max and -52.5mV min.

All these were taken with the test load set to RED LD and the power supply set to 3.7V right off teh battery.

 

[Kmor2004]

After fidgeting with the code a little bit and some Help from Trevor, I got my serial PWM control done so now I don't always have to re-program the chip every time I want to test a different driver current, now I just have to type in oXXXX, o telling the 328 that its for the PWM on-time which controls the drivers current setting, and the XXXX is the value to be placed in the buffer with a range of 0-1600, I may adjust to 0-1000 and increase the PWM frequency to reduce noise on the drivers output.

With the exception of some much-needed fine tuning of the math that goes on inside the 328, I've made a short video, that at least proves that most of the functions I've claimed are actually working, I'm pretty pumped up about the progress and it all actually working in a system so far.

First I must apologize for all the background noise the fan on the TEC heat sink is loud and my PC is about 6 inches away with a LOt of dirty 90mm+ fans, anyways at the beginning it shows everything at 0 with the exception of the Battery voltage which is the actual voltage AFTER the zener diode (to drop the voltage from 6-8.3V to 5V or less this also helps with the Low battery alarm, which isn't shown but atm it just flashes "LOW BATTERY CHARGE!" in the middle of the screen, later I intend to include an audible alarm, and the lase minimum and max current which isn't programmed into the display yet since it's one of the touch screen features.

Then you'll hear my clanking around on the keyboard typing in o800 or about 50% duty cycle which is a little above the transistors minimum on voltage which kicks in at 700 count or 43.75% duty cycle, then i change the setting to o1000 which is 62.5% duty cycle, one more change to o1600 which is full on, then I drop it back down to 0 since after about 30 secs the board starts to get pretty warm from all the heat generated by the diodes, I still have issues with the hold function for the numbers, the beeping in the background is me changing ranges on the oscope.

Then finally I demo the LPM portion using my 445nm that I had Jake measure (Thanks Again Jake) at 1242mW or 1.242, so with out further ramblings here's teh video:

 

[ARG]

Wow! That's amazing! Is there a chance of you selling kits for these?

 

[Kmor2004]

Not very likely, since the Display alone is $80, figure $12 a board, and $50 or so in parts, your looking at $150.

However if Trevor incorporates some of the same stuff into his Open LPM MK I or II, that would actualy have good datalogging options, then it might be more for what some one is looking for, otherwise if anyone wants the 2 spare boards I have and a parts list I'd have no problem doing that, and if wanted I could through in an pre-programed 328 after I get all the bugs worked out.

 

[random person]

Showoff! =P
Very impressive demonstration of your skills there.

80 usd for a display? ever consider using one of the far cheaper LCD displays out there? They got decent TFT displays in 4in+ range ..ect for about 15-25? Why are you using a 80 usd screen? I assume because its easy to drive? I know very little about LCD screen driving. =( Only worked with a 1602.

 

[Wolfman29]

This is awesome! But what's the difference between driver setting and current reg?

 

[Kmor2004]

I chose that display because I already had it, and it didn't have a purpose so I though "Portable LPM with graph and battery operated OH YEA!"

As for actualy driving the display, here's the link µLCD-32PT(GFX) - 4DGL Display Modules, it has a chip built into it that gets programmed directly and I i'm doing is sending serial data to it, is it overkill very much, especially since I have a monochrome graphic display thats just sitting around also, but I figured the 3.2" with touch would reduce the number buttons or switchs needed, and it would be fun to mess with.

The intended difference between the driver setting and the current reg is that the current reg is actualy current sense I need to change it, but it's the voltage across the 1ohm resistor indicating how much current is flowing through the LD or the test load, the difference atm is that the current reg is 1/2 of what the test load is but has been multiplied in the chip to be the same or close to it, and the driver setting is measuring the voltage coming out of DAC into the transistor and it still needs some math done to it to actualy work as intended and to say something more meaningful like 100mA or 500mA limiting rather then 2.35V into the transistor.

I should work on the code a little bit more for that stuff but I wanted to give the display a rest and take my mind off the code and work on the case, interfaces and cleaning up the mess of wires, as well as find ing some useful tasks for my 445nm, such as shrinking my heatshrink tubing and making reference holes in my enclosure of sockets. jacks, and switchs, except atm I have the epoxy setting up for the PCB standoffs, so I may just have to work on the code again HAHAHA.

 

[Wolfman29]

Oh, neat! Post more pics when you are done!

 

[Kmor2004]

The epoxy finaly set up enough for me to pull teh blank board off without moving the standoffs, and I got most of teh soldering and case work done that I wanted to get done for Sunday (it's 4am :tired heres the lower half the encloosure without the batter pack:

Brought it back to the table to connect the LCD, battery and ll the otehr test equipment, it makes me happy :yh: that a lot of the wire mess and clutter is gone:

Because of a thurough lack of planning and design, earlier when I went to make a vid of the driver portion, that when I flipped the switch for driver to drive an external load that I wsn't getting anything on the LD...then it hit me, ATM the switch'S were both set up for only the internal test load, and because I hadn't figured out how I was going to make unit nice neat and portable with a detachable TEC, I finaly settled on getting some gator clamps, 1/8" plugs and jacks, 1 for the TEC, one for the driver, 1 for the Test load, and 1 for the TEC's fan.

Now instead of having a bunch of switchs and having to remember what positions are needed for test oad and driver, internal or external, now if I want to run all the internal stuff, DRiver and testload I just gator clamp to gater clamp, if I want to test a driver I can just plug in the test load and connect + and -, or if in the case of this video I want to test the driver out on one of my 680nm's I can just plug in the gator clamps, clamp them to the LD under test AIM at the TEC and go.

Actualy this video is just me making sure the Diver is getting to thresh hold and the current sense resistor is pick up some reading.



Now the fun begins, now I actually have the LD pointed at the TEC, Hmm wonder what happened at the end, just after raw output power peaked?

(This video may not be up till some time later today)



Here's what teh LPM read just after it peaked.

Finally here's what the test load measured I'm pretty sure the math that the micro is using is wrong.

 

[Helios]

That is awesome. A little hard to understand what exactly is going on during the video but if you were to narrate it as you change values I am sure it would make more sense.


Have to plus rep this