Savel brain dump in English!

From time to time I am doing house clear-up. If I didn’t this, the house will be full of various electronic stuff. Some of the items maybe sold in eBay or local garage-sale, but some items must be thrown away.

Some stuff appears in the house in very simple way- I need some small part on the PCB, so I pick up whole PCB. And the rest of the board is left in the shelf- maybe I’ll use other components in the future. But not now IS THE TIME and everything must go away.

In the picture there is green PCB with big BGA chip, near two gamepad joysticks. This PCB was picked up only for FM75 chip- tiny element with eight pins. I also removed some linear regulators from this PCB: 1.8V and 3.3V. They were used for FPGA breadboard. All other chips like big LG cpu, 28LV320AT flash, LV logic chips, LEDs, 100MHz oscillator and lots of SMD components are trash.

Here is bigger picture of the trash to exam.

Here is the list of the trash: Logitech web cam (old one, slow, low res and low sensitivity. Replaced with new no-name), VFD screen with drivers from DVD, TI DSP board, few gamepads (I removed radio modules), CB radio with broken display panel, computer mainboard, old IBM notebook (I removed only few chip from it), some optical mouses (I was searching for specific chips), one wireless mouse, bunch of small motors (gamepad vibrators), some unidentified PCB, some old DIMM and SIMM modules, old HP 5300 scanner (replaced with new-old HP6300 with better lamps). This is my fourth scanner- and only first one (HP5p) was bought in the shop. All others were picked from the trash. These old scanners are much better than new cheap ones .

All this stuff is found in my room. And if we’ll look in to the garage…

As I mentioned, laser diodes are fragile devices. So the power supply must be adjusted before connecting any laser diode.

After all components are placed on PCB and visual inspection is finished, connect one 1.2K resistor in R4, R5 and R6 place. Power up the circuit. Check if linear regulator is working and we have stable 5V in the 7805 output. Measure voltage in the empty laser diode place. It must be less than 5V. Connect ampermeter instead of laser diode. Ampermeter must handle 1A current. In one position of the trimmer, the current in zero, in other some value. Set max current value by adding additional resistors in R4, R5 and R6 place. It is not very important to use exact resistor values in this circuit. Something in similar range is usable. I place 13K in R7 and everything is fine. Graduate trimmer to output current values.
Connect in series to ampermeter any powerful diode (I used optically burned laser) and check the current. It must be same as before and trimmer scale must be same.

This device must be powered to power source capable to output ~1A current at ~7V. If input voltage is higher (I use 12V Pb battery) the 7805 gets hot at max power. Use any heat sink to keep devices in working temperature.

Usage:

Connect (solder) laser diodes only to switched off and disconnected device. I repeat- DISCONNECTED. I damaged few laser diodes due to ground loop effect. The voltage between switched off laser power supply and ground soldering iron was high enough to damage laser diode.

Set current to min, switch power supply. Increase current. At first, laser diode is only glow. It is simple LED emitting effects. Optically burn out laser diodes can emit LED light. Increase the current and in some moment, laser diode start to shine very bright- it means that laser generation started. Now you can increase the current up to mentioned in datasheet. Or just try to find max current by your self. High current kills diode, so be careful. Especially when testing burning and ignition experiments*.

IR laser from CDRW device is powerful too. It can withstand 200…300mA current, but “working” current is about 100mA. IR laser beam is invisible and if you use digital camera to watch IR light, be careful. You can burn out not only your eyes, but digital sensor too.

Do not forget to use heat sink on lasers. In max power mode even quite big heat sink become hot.

Also, don’t forget laser safety… (image from www.electricstuff.co.uk – BTW nice web page)

*more experiment will be translated in near future. Take a peek to Lithuanian blog.

I’ve made some improvements to my laser PSU. I added voltage regulator, max voltage on open laser suppressor, spike suppressor. Also some useless improvements…

I didn’t made new PCB, I tested modifications on old board. But all modifications I entered into Eagle software and traced PCB.
I think this “theoretical” PCB is good.

Main difference from old version: IC2- 5V voltage regulator, C4 capacitor, R11 resistor. Capacitor C2 must be very small. It is used to prevent high frequency oscillations. If the capacity is too big, it will shunt input of amplifier and the inrush current through the laser will be very big. PIN2 theoretically is connected to photo-diode build in laser. But all new high power lasers don’t have photo diodes. So this pin typically is left unconnected. So, the resistor value is unknown. D1…D3 are fast schottky diodes. They prevent from reverse voltage during various experiments and connections. One of them is useless.

Laser diode body is connected to regulated supply, so take care that heat sink and laser body is not connected to ground plane. If it is connected, your laser is dead. It is possible to build PSU with grounded body, but I don’t have p-channel power mosfet in my stock. Laser diodes are static sensitive devices- handling precautions required. I damaged few diodes by simple ground loop- my solder iron is grounded and laser was powered from some wall adapter. Ground loop killed diode. Disconnect laser PSU from main while connecting/soldering laser diode.

Use the link and make your own PCB using UV of hot-iron and laser printer method.

PCB image (600dpi).

Here is experimental board (version 1 with modifications):

I improved my laser PSU design: added voltage regulator, additional schottky diodes, some capacitors and it seams that laser supply is quite stable. I tested it with low power led lasers and several high power IR lasers from CDRW devices. Heat sink on the PCB is not mandatory. Only in rare cases, when powered from 12V and using extra power to diode, PCB is hot. As I changed some resistors, the current range is smaller. I decided, that I will not try to pump extra power from these small lasers. Now the range is from 0 to 200mA.

There is two lenses in the photo near PSU. I removed these lenses from photocopier. One lens have build in IR filter, other lens is made from clear optical glass. The bluish color of filtering lens is from copper ions in the glass.

And now, small experiment about wavelength filtering. Take note, that IR laser is much more powerful than RED. Red laser in this experiment is from cheap DVD player.

As we can see, special lenses filter IR light quite efficiently. Similar IR filters are placed inside all digital cameras. Sometimes it is possible to remove this IR filter and get very weird IR camera. The problem in modern USB web cams is, that IR filter is build in camera’s lenses and it is impossible to remove it. The RED beam cross both glass lenses without any visible problem. (Color change of the photo is due to white balance- digital camera set bluish color as white base).
The current through the diodes in both case was about 40mA (IR laser is in low power mode, for “reading”).

Small movie: IR laser. 100mA. From CDRW. Unfocused. (xvid, 1.5Mb)

My red laser stock was empty. Mainly due to my errors and experiments. As I didn’t find spare DVD recorders, I switched to infrared lasers (IR). It is much easier to find powerful IR laser- the source is any CDROM recorder. In newer high speed CDRW devices, lasers are quite powerful.

IR laser beam is invisible. Sometimes you can see so red light emitting from laser diode (do not stare to focused beam). It is not a miracle- you can’t see these wavelengths. It is just secondary LED emission near the cavity of the laser. Even if the laser part of the device is burn out, you can see this reddish light. Laser emission is very interesting phenomena- when we increase the current through the diode, we get LED light. As we increase current, suddenly optical generation starts – laser process is on. All low power and old lasers have photo-diode to detect this process and to measure optical power. New high power laser modules do not have photo-diodes installed, even the laser is in 3 pin package. You can notice, that third pin is not soldered to PCB. And if you disassemble laser itself, you can see, that there is not wire connected to this pin. Neither you can find photo diode. I wanted to get modern driver chip datasheets from elentec-intersil, but I received answer, that these documents are not for wide publication. Why? I don’t know. These chips are in every modern DVDRW device… So I can’t find how laser power is regulated in these devices.

I improved my power supply and started tests with lasers. Did I mentioned not to power high power laser diodes without coolers? So don’t.

To detect IR beam use any digital camera, USB camera or any other consumer device with CCD camera. CCD cameras’ have IR filter, but it is to weak to block laser beam.

This nice photo is made when I placed my digital camera lens to CDR recorder optics. As optics is untouched, we can see nice interference pattern. Just cool photo.

This is first version of laser diode power supply. I borrowed circuit from die4laser.com and changed it a bit. It is classic current source using n-channel power device. It is better to use p-channel devices here, but now I have only n-channel mosfets on my workbench. They are cheap and easy to get. Modern mosfets a very compact and powerful devices. Now they are very steady devices and even can work in very high temperature. During experiments I overloaded supply and transistor self-melted solder (I am using lead solder)- working temperature of particular device is 150oC!

Resistors R4, 5, 6- they are used to set max current. R8- is shunt. If we place here 1 ohm resistor, we get 1V reading for every ampere. R2, 9 -1k. R1 is about 600 ohms. R3, C1- is soft start circuit. Not implemented in current design. C2- only few hundreds of picofarads. Only to prevent from auto-generation. C3- is a bigger one. Transistor- any n-channel mosfet powerful enough to carry working currents and voltages.

This is PCB image. If this picture is printed with 200dpi resolution, it can be used to build PCB.

This WAS prototype of power supply. It killed few laser diodes. So I made another version and I place circuit diagram in next blog entry when I’ll translate it from Lithuanian version. I recommend to use regulated power supply and not more than 5V.

There are lots of rumours in the internet about high power DVD lasers and about hacking them. I decided to test some of the rumours. Theoretically, there are two lasers in modern DVD recording device. Power of the laser must be strong enough to change the physical properties of recordable media. In this post, I didn’t examine IR (infra red) laser used in same device for CD/CDRW media. I tested RED laser used in DVD recording and reading. The newer DVDRW device, the faster recording speed- the more power in laser.

Laser diodes is CD/DVD drive come with various optical lenses. These optics is not very useful for burning experiments- the laser beam is separated and then focused in very short beam. And for real “laser gun” we need long range optics. There two types of laser diode modules- stand alone lasers and lasers with multiple photo-diodes (detectors) in same package. Older laser diodes were built with photo diode build in package. This diode is used to detect laser generation and to measure optical power. In some new devices this diode is missing. Even if the package have three pins, I didn’t find photo diode inside, even when I disassembled diode.

Laser diodes are sensitive devices. Especially they are sensitive to static discharges and over voltage-over current modes. I damaged 4 diodes experimenting with my power supply- the transitive process during power-up and power-down killed them. On some laser diodes there is optical element glued to package. It is beam splitter- you can get remarkable interference lines when using these splitters, but for power experiments we need to remove it. After removing, the “can” is open to free air (and some diodes are made without protection), so keep “open” diodes dry.

Laser diodes, same as LED diode is current, not voltage user. But using simple ballast resistor is not good way to solve the problem. The PSU for laser diode is current regulator with dual feedback: one from current, another from photo diode. And PSU with over voltage protection. The PSU is very simple (I’ll post two version of PSU I build). The components are very cheap and everything can be found in old computer motherboard.

Here is the image of working DVD recording laser diode without collimator optics. Other, simple diode without heat sing is seen too. Never use high power laser diodes without heat-sink. The current in threw this diode is about 150mA and according to the datasheet, the optical power is about 100mW.

If I place diode to my digital camera lenses I see such nice image. The light is dissipated, so there is no possible damage to camera detector.

Here is first experiments trying to focus laser beam. I used optical collimator some some old IR laser. This collimator is not very suitable to high power RED lasers. There is big problem to get good collimator for such laser.

And now some words about safety. Lasers used in DVD-R device and working in full power are potentially dangerous devices. So: NEVER STARE TO LASER BEAM WITH REMAINING EYE! IR (infrared) laser are double dangerous- they are powerful and invisible.

I found datasheet for Rohm laser diode RLD65PZB5: max optical power (pulsed, 50% duty cycle) is 240mW! Current according datasheet is about 400mA.

I would like to introduce part of my workbench. It is computer side of my workbench. There is electronics workbench, but it is not described here. I’ve made some order here before making pictures- regularly there is a big mess here:

Small description of the stuff:

1. Very old, >20″ SGI (Silicon graphics) monitor. It is time to throw it away, but from time to time I need to connect so old unix box of some PC with nonstandard video timing. This monitor is capable to sync to very wide range of sync signals (or even without them- sync on green). The only problem is rare 3W10 connector. I’ve made some cables for it. Very heavy.
2. Some old unix boxes: SGI Indy, Sun Sparc Xterminal 1 and Sparcstation 5 (from recent blog entries you may understand were I found last one). And what is displayed on CRT screen.
3. My regular computer, every day it is getting older and weaker compared to new ones. It is P4, 3GHz, HT computer. (nor D, nor Duo). with some SATA drives and 2GB of RAM. I was sick of out-of-RAM messages and virtual memory performance. Now memory is cheap and I recommend to invest some money to RAM.
5. Two 14″ LCD monitors. I love Lot’s of desktop space.
6. some HDD.
7. Black keyboard. I love classic small keyboard. I hate “natural” keyboard and keyboard with “media keys”.
8. Classic Russian tea cup. Regularly I drink white coffee with lots of sugar.
9. Sun keyboard. It is only connected to test sparcstation.

And now backstage…
Read the rest of this entry »

From computer tomograph PSU, I removed battery of capacitors. It is 12 high power electrolytic capacitors. 6 x 12000μF and 6 x 8200μF. All caps working ant 400V (450V surge). Total 121200μF (0,12F). We can charge them to about 400V and store about 9696J of energy. Lots of energy. And lots of lethal energy. It can kill you.

More about capacitor calculations in older blog entry.

I achieved personal top record in braking electronics. Today (Nov 14th) I disassembled computer tomograph. As whole device was too big to fit in the van, I don’t have classic photos of the doughnut (donut). I have only partly disassembled device images.

Here is the images of “super computer” displaying human body slices:

In fact, it is very old, Sun Sparcstation 5 computer, with 256Mb RAM, some external CDROM and hard-disk. With SunOS and Philips software.

Here is the remains of donut. The device was ancient. It was made in 1995, but the design is much older. Main custom computer is made using DIP chips in 5V technology. The only identified CPU was MC68020 working at 16MHz, and several custom made or maybe MIPS CPU’s on several printed circuit boards.

It was X-ray tomograph. Images are produced using rotating x-ray tubes and 192 detectors. This whole bunch of heavy metal is rotating around human body. This system is powered from 380V 3 phase mains system. The power is converted to higher frequency, so all x-ray high voltage transformers are much smaller. But main PSU is very big, full of big capacitors and power IGBT transistors. Lots of power is used for such device- mains braker is 250A.

As device is very old, only few interesting components were found inside. It was great disappointment.