Savel brain dump in English!

Everybody knows outdoors security cameras hanged on poles, house corners and other places. Typically it is white, gray of silver colored boxes with small windows in the front. Like these:

What is inside this box? Here is one opened, but without lenses.

Contents of the box:

A) heating element. Just small heater to heat the housing and especially the lenses and window. To remove possible fog.
B) here must be lenses. Sometimes with special iris driven by camera body and sometimes moving system to change zoom, focus or even viewing angle.
C) camera body.
D) this is 12V wire for camera body.
E) heater’s thermostat. It is set to max 25 oC temperature.

Not in this housing: the PSU for 230VAC/12VDC. Some camera bodies can use 24V or 230V AC supply.

In my case, the camera body is 12VDC, heater is 230V and PSU is ugly, made in Poland transformer. It was quite hard to place this transformer inside this housing. Also simple transformer PSU it is not very suitable in mine case. The AC power is very unstable and often is missing. So I decided to remake all system to 12VDC only. I need to change heating element and ensure, that 12VDC power supply is quite powerful. I am using switch-mode PSU with 5A max output current.

For my video surveillance project I needed special video camera to make video shots in the dark. One local company offered YOKO YK-3B41 or YK-3B43 video cameras. The body, lenses and IR emitting diodes are located in the same box. The box has IP65 class and the manager in that local company told, that it is waterproof.

Inside there is Sony CCD, 12 IR light emitting diodes. 12V external power supply is needed for this device. The diodes starts to glare only then when light situation is poor.

As digital photo camera is sensible to IR wavelength light, you can see how IR diodes glares in the dark. In fact, the diodes are a bit overloaded and you can see red light with bare eye. One interesting side effect from IR light is that you can see blood-vessels under the skin if camera is used in complete darkness and is quite near the human body. Normally vessels are invisible 🙂 .

Camera was recommended as watter proof, but maybe the particular one was defective or it was only advertising myth. I played with video camera for a while, holding it in my hand and suddenly the sharpness the video image disappeared. Short glance to the lenses solved the mystery- there was fog inside the camera body, against the lenses. Somehow, the human humidity managed to enter “waterproof” camera body. The only good thing is that the mist disappeared from it after some time.

Another bad side of this camera (and all other cameras with IR backlight near the lenses) is that all the dust floating near the lenses are reflecting IR light and whole image is full of “ghosts”.

And the last comment- this model of video device is using fixed objective lenses, so it is impossible to adjust sharpness of the image.

Conclusion: expensive toy. Usable only for general surveillance.

Long time ago all my computer were suffering from low memory. I always remember how my work computer lagged when I loaded bigger application and how that virtual memory was chewing harddisk. Especially when I loaded few programs at same time like in my home Amiga computer. Now I am trying to put as much RAM as I can.

All recent software and OS are very memory hungry beasts. But optimizing Windows I reduced memory usage. Now I need only ~150megs to run XP Pro. I don’t like bells and whistles- I kill all pop-up and useless software. Look at your Windows computer lower right corner. All these fancy icons are using RAM and your CPU power. Are they important?

My computer had 1.5Gb of RAM. Today I upgraded 2 DDR2 modules from 256 to 512. Now my computer mainboard is populated with 4 pcs of 512Mb DDR2 RAM modules. 1.5 gigs was enough for my work. In fact, I never filled all the RAM, but my windozeXP complained few time that it is low of virtual RAM (I manually set the size of virtual RAM). Microsoft can’t write programs working without virtual RAM 🙂

Here is the screenshot of task manager:

As you see, my computer is optimised for low RAM and CPU load. I stopped all shitty popup software and unused windows services.

In one company, the security situation is awful and we decided to install security video and record everything. As the facility is quite complicated, we squeezed only to 8 video cameras. In Lithuania you can buy various video in devices, but when you need 8 channels or more, the assortment is quite small. I selected quite expensive, h.264 standard (MPEG-4 part 10), hardware compression video capture card. It is VG8C-RT4:

The main peculiarity of the card is that it has two Texas Instruments DSPs on board (digital signal processor). The DSP is converting and compressing video, so main computer CPU is not loaded. All free computing power could be used for other interesting purposes.

The computer itself is new too. Maybe it is too powerful for this purpose, but I selected Intel Pentium 4 Duo core, 2.6GHz, 1Gb RAM and SATA hard disk. As I bought computer without any other bells and whistles, without CD/DVD/FD/Monitor, the price is much lower compared to video capture card. Also I selected Intel made, Intel chipset mainboard with extended warranty. I hope, that this computer will do it’s job for a quite long time.

Here is the first tests. I need to get familiarized with unknown hardware and software to me. I don’t have so many video sources at home, so I only used 4 channels. I used 3 video cameras’ and one video output from TV set.

Four channels in full-screen mode look quite impressive.

As local sale of tubes is not satisfactory for me, I decided to build new, full, power amplifier from scraps and surplus components. It will we classic tube amp with double tubes on the output. Why this type? Because it uses lots of tubes and I have transformers.

The main component for tube amp is cool case. Tube holder places are made from old computer case. I used some “branded” and very old computer, so the steel is solid compared to new Chinese made computer cases. The round holes are made using step drills on some drilling machine.

The case itself is some 19 inch box from some old communication device. It was some serial switchboard of something. There was lots of these in local scrapyard and I made one major mistake- I didn’t stored more boxes for myself.

In this photo you can see the tubes and PSU installed. Even 75% of tubes are connected to heater. The output stage is made from old classic- 6П3С (6P3S, EL34). The phase inverter and preamp will use some tubes from 12AX7, 12AU7 or 12AT7 range. As I have lot’s of these pull-outs. The mains transformer is with nominal 100W power. This is not some Chinese Watts or other RMS/SRS Watts used in western sale-market world. Nominal power term was used in Soviet time to describe real power of device. This means, that device can handle such power for infinitive time without any harm. Regularly, this means, that power of the device is 50…150% more powerful than stated.

This is the beginning. The rest will come…

Few years ago, our major internet provider offered NOKIA DSL modems for end users. It was Nokia NP5121. It is very durable hardware. I know few places were such modem is working without any problem for six years.

This DSL modem has the secret. With simple firmware flashing you can convert it to more powerfull Zyxel Prestige broadband router/bridge. So if you are sick of that damn PPPoE stuff on your computer, want instant internet access or want to connect more computers on same digital subcriber line, you can reflash your modem.

I aquired old Nokia modem from scrapyard. It was with small problem- the power connector was slightly damaged. I resoldered it and I was fully working device. The reprogramming procedure is described in internet. I posted here the shorter version for advanced user. Novice user can use this procedure, but some moment can be harder.

First of all, you must download firmware from zyxel site. Search for Prestige 642 R model and firmaware must be at least R11 version. The older revisions had security bugs and is not recomended to use. Search for file “p642r11.zip”. Also, you must find modem cable with 9 pin connector. You can use cable from old modem or solder it by yourself. Just get two 9 pin d-sub connectors: one male other female. And a peace of UTP CAT5 cable. The pinout of the cable is very simple- pin 1 of male connector is connected to pin 1 of female connector. 2 to 2 and etc. Leave pin 9 not connected.

Connect Nokia to your computer. Selectr serial port in you hyperterminal program, set it to 9600 bod speed, 8 data bits, 1 stop, hardware flow control. Set you hyperterminal program to VT100 terminal emulation.

Switch on modem, press enter and you must see something like:

password

Type “nokia” as default password. You must see command prompt:

MP5121>
MP5121>config reboot

Press any key to enter debug mode withing 3 seconds.
...........

Press Enter

Enter Debug Mode

You’ll see big list of available commands… We need only one, to increase console speed as using default speed will took lots of time to transfer new firmware. Attention, the prompt dissapeared as we are in debug mode.

ATBA5
Now, console speed will be changed to 115200 bps.

Now we need to reconfigure the hyperterminal to new speed. Set it to 115200.

OK
ATTD
Starting XMODEM download...

This is old settings backup. Set receive mode in terminal and select xmodem transfer protocol.

Total 13384 bytes received
OK

Now we begin new software upload. First of all we need to upload new settings. They are in zip file with ROM file extension.

ATLC
Starting XMODEM upload (CRC mode)....

Now select file send in terminal menu and select xmodem protocol.

CCCC
Total 16384 bytes received.
Erasing..
....
OK

And now main step. The new firmware.

ATUR
Starting XMODEM upload (CRC mode)....
CCCCCC

Now we need to send the file with BIN extension from same firmware archyve.

Total 1010048 bytes received.
Erasing........
........ (lots of dots).......
OK
System Reboot...
Console speed will be changed to 9600 bps

Reconfigure terminal software to 9600 bod speed. Enter new default password “1234” and see new bright MP5121 router configuration menu:

If you need simple regulated power supply, you can build it using typical old chip LM317 (LM117). Here is the abstract from datasheet: The LM317/117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators. Also, the LM117 is packaged in standard transistor packages which are easily mounted and handled.
In addition to higher performance than fixed regulators, the LM117 series offers full overload protection available only in IC’s. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment terminal is disconnected.
Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators.
Besides replacing fixed regulators, the LM117 is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e., avoid short-circuiting the output. (end of abstract)

I only can add, that the power dissipation rule as mentioned in older post about linear regulator is working here too.

LM317 is usually made in TO220, transistor package. There is difference in pinout compared to 78XX series regulators. The output of the regulator is connected to the screw tab. There are also other types of package. SMD packages are made too.

This is typical circuit from the datasheet. Theoretical output voltage is from 1.2V to max about 28V. Using floating regulator trick, the output can be higher. Max current with TO-220 case is about 1.5A (you max calculate power dissipation and select proper heat sink).

I connected circuit on the breadboard. I used trimmer instead of resistors. I think, it is possible to use any trimmer form 3K to ? kilo-ohms. Somehow I didn’t managed to get 1.2V output even when I connected regulating pin to ground…

This blog entry is for beginners. Sometimes I receive letter with questions from beginners.

So, the question: how to build very simple voltage regulator? For fixed (3.3, 5, 6, 12, 15V) or adjusted output. The simples way is to use special chip- linear regulator. The unnecessary voltage are disposed by the heat. So this type of regulator typically use heat sink. As bare chip version is only of a few watt power output.

According to the datasheet, there must be some capacitors. But the main element is three leg element. Center connector and the screw tab is connected to ground.

The chip can be named with various additional symbols, but the main series of those chips carry 78xx mark. For example, the 5V regulator is named 7805, 12V – 7812 and etc. The full name for chip for national semiconductors is LM7805C. The low power version carry 78L05 mark on the body of the chip.

Soviet copy of the chip is called “KREN”. It is from shortened marking. The full name of Russian chip is КР142ЕН5 (for 5V version). The chip is carrying shortened version “КРЕН5”, and it sounds like “KREN5”.

TO220 case chip can pass 1…2A current (depends of model). Typically the chip has build in protection from over current and overheating. But always check the datasheet. Max temperature of the case is 70…80 degrees of centigrade. Theoretical maximal power from the chip is 20W using endless heat sink. Bare chip can dispose about 2W of heat. Using real heat sink- 5…10W. How to calculate this power? Just few lines of math:

For example, we want to build some PSU to use in the car. Typically, the power in the car is from 12V (when engine is off) to 14V (with started engine). Assume that output will be 5V @ 1A. We must calculate with biggest possible values.

Udrop=Ucar-5V=14-5=9V

The power dissipated on the regulator:

P=U*I=9*1=9W. (And is the current increases, the power is going very high- at 2A it is 18W)

So, we must dissipate 9W of heat. It is more than 1…2W, so we need heat sink.

Sometimes, when connecting regulator to wall “brick” adapter we must use the heat sink, as output from rectifier is much more than stated on the label. Measure the voltage with required load. I’ve seen adapters where output was 25V at 250mA load when label was 12V!

So:

P=20*0.25=5W (!) And we need heat sink with this adapter. Especially if it is placed in closed box…

One more parameter- max input voltage. It is about 35V for 7805. Read the datasheet.

Other interesting parameter minimal dropout voltage. This means how the voltages must differ from input to output to put linear regulator to normal working condition. This can be obtained from datasheet. For example, 7805 need nor less than 7.5V input. There are new series of low dropout voltage regulators. Like LX8383. It need on 1.3 … 1.5V dropout for normal work. The max current is much more- 7.5A max, but the input voltage is much lower.

How to make adjustable regulator? Very simple, just enter resistor network to divide voltage:

Similar resistor network can be used with 78xx chips. It is possible to put trimmer and to adjust output voltage. Later, it is possible to measure the resistance of trimmer’s halves and replace trimmer with regular resistors.

To adjust output we can place zener in the gnd line. The output voltage will be equal to regulators voltage plus zenners breakout voltage. For example 7805 and 1.5V zener will output 6.5V.