Bojan Pavsic

Eurobricks Citizen
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About Bojan Pavsic

  • Birthday 11/06/1977

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  • Location
    Maribor, Slovenia
  • Interests
    Computers, Electronics, Lego (not specificaly in that order)


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  1. 16:10 14:6 21:4 9:3 2:2 13:1
  2. Acording to Philo's research, a train motor (RC, PF) uses about 400 mA but in stall condition, PF pulls out 1.3A. That's somewhere between 1.5C and 2C (for your batteries). Since we don't know what max current they can take, i'd say it's unsafe to use them. Another thing i don't know is the presence of PCM (protection circuit) or lack of it inside the batteries. IF there is one (in each cell ofc), then it probably has max current and overdischarge protection. That means that u can combine any of the 2 batteries and the pack will last as long as the smallest of the batteries will last. !!BUT!! if there is no PCM inside the cells, you'll probably end up with cell failure (the smallest one) or if u're gonna use it in an "emerald night" type of train, with a smoke (not really high probability since we're dealing with not that much current here, but it can happen) :D]And a little guide on LiPo's[/url]
  3. Because of the internal resistance. Different types have different resistances, which means in 2S configuration (2 cells serial), that one of the cells will take more load then the other and that leads to cell failure. That's why good packs have cell balancing (which makes the cells have the same voltage while charging them). Even same type of cells, same capacity different age is not recommended. If you have the old NiMH, NiCd or newer LiFePO4 cells, it's not that big of a problem (it's still not good for the cells and not recommended), but LiIon and especially LiPolymer are dangerous. They can catch fire, explode etc.. if they're not handled correctly. And btw, it's not current, it's capacity (mAh).
  4. Short answer: No. Long answer: First of all you'd need to connect two batteries in serial, so you'd get enough voltage, but that's usually done with same type/capacity/age batteries. From your picture, i can see you have 800 mAh, 860 mAh and 940 mAh batteries, so that's the big "no-no".
  5. Bojan Pavsic

    Train automation - upgrading PF

    After the whole weekend "testing" at our local LUGs Lego event, some minor glitches came to the surface. The motor driver chip has a Chip Enable line, that has to be pulled up to enable the chip (it's a power saving feature, so u can disable the whole driver if not needed). The thing is that the driver works at 9V and the micro-controller works at 3.3V. A "1" from the uC can cause problems in case of little voltage drops (especially when multiple motors are driven). We had 12V LED strips powered at 9V too and the these voltage drops caused the driver to disable which again caused flickering of the LED strips. At site, i had to cut the CE lines from uC to the drivers and pull them up to drivers power supply (with a resistor ofc) so they were always on (They used up a little bit of power even when all outputs were off, because of the internal chip logic, but that's so low that it isn't really an issue). All in all visitors (especially the kids) were very happy pressing the buttons and watching what they start. I implemented some additional options like a command that starts a motor in one direction for some time, then switches the direction for some time (a motor was moving a boat out of a cave, then brought it back inside). Another "special" command was random flicker of LED lights in some skull head eyes (like lightning). Back to the drawing board now... implement a couple little PCB changes, have them made and finish a "final" version :)
  6. Bojan Pavsic

    Train automation - upgrading PF

    @SpokaneSteve Yea, sound module was one of the future options too. PF has 7 speed stages, my receivers have 100 (in %), but you need to keep in mind that at low duty cycles motors don't have as much power so many of that 100 stages aren't useful at all. And finally, i'm not into making this a commercial product. I will publish the PCB files, firmware source and everything so everyone can make them (the problem is only that they have to have some knowledge about it). @Rob Klingberg I wasn't talking about WiFi modules connected directly to the receivers. I will keep using the 2.4GHz cards, but i intend to make a WiFi gateway that will just "forward" the commands from the WiFi network to the RF one. Thanks for the info about the cables. I was actually looking at]Corsair Style cables[/url]. They have them in 18 and 22 AWG with 3, 4 or 5 conductors. The thing is that i'll need to buy a "sample" quantity first to see if they're what i expect from them. Then i need to check if they're compatible with the connectors that i'm currently using.
  7. Bojan Pavsic

    Train automation - upgrading PF

    @freakwave No, i didn't. Tbh, i switched from PIC to Atmel some time ago. Atmel also has some RF series, but tbh, these uC are hard to get and cost more. About the spectrum. I was checking out 433, 868 and then switched to 2.4gHz... Reason: cost of the RF modules. I bought 100 pcs of RFM73D for about 120$. There's an alternative too... NRF24L01+ which has a different connector (2x4 @ 2.54 pitch while the RFM has 1x8 @ 1.27) but is pin to pin compatible. Even registers and everything is like 99% identical and these can actually be bought for less then 1€ a piece (thou it's slightly bigger overall). At first i wanted the same (retrofit - exchange the PCB in the IR receiver), but then i actually wanted it smaller then the original so it could be fitted in a 4 stud wide model (by using panels on both sides). That's why i settled for 3x4 dimension. @JopieK Yea, those aren't bad, but i wanted a custom board. It'll have full PF compatibility if the IR communication card will be used. At some point over the year, i made a PCB with an ARM processor (LPC 1114) which is an Cortex M0 microcontroller. I took the small one in QFN package (5x5 mm) and i also had the drivers on the same board with additional 4 mosfet outputs (so 4 pwm motor + 4 pwm mosfet for leds & stuff). I scrapped that because it was hard to solder (thou i have hot air station). The biggest problem on a board this small are actually connectors. The power supply has to support 6 amps (each driver has two 1.5A outputs and there's 2 of them). The motor outputs have to support 1.5A each. Even AWG 22 or lower flat cables are soooo hard to find (practicly there's none, at least not any that i found). I'd like cables that TLG uses, but can't find any that would support 1.5 amps. XBee is nice. But costs a lot. What do you mean by concurrency capabilities? How many can be controlled at once? Didn't try more then 2-3 for now, but since the RF comunication goes up to 2 mbps and i'm sending like 6 bytes, the transmit time is very short. And the RF modules have built it retransmision and acknowledge, so no worries whatsoever. @dr_spock Well, depends how your switches are motorized :) If it's PF/9V motors, then yes, ofc it can. But i'll add another part that will support RC model servos which can be very small (i have some in dimensions of a 1x2 brick - will try to control switches with them). I'm getting a 3D printer in a couple of weeks and i'll try to print some housings for the receivers and some lego compatible RC servo holders etc...
  8. Bojan Pavsic

    Train automation - upgrading PF

    Not sure if i can post an ebay link here, but it's the SM157 LiPo PCM. China made :) But i already got sample ICs from TI and i'm planning on building a full blown BMS with primary & secondary cell protection, gas gauge, sm-bus (which is basicly i2c that already exists on the receivers so it can gather battery data and send it back...). The cells are Turnigy nano-tech 1200 mAh which are used for hobby/model RC planes, cars etc... Well, yes, it's a replacement for IR (the RF cards support up to 5 byte addresses, so basicly unlimited, compared to 4 channels with PF). But i will probably make an RF transceiver pin-compatible IR sensor that can be used to use the receivers with the original PF controllers. Another thing is to replace the PCBs in the original controllers to add support the RF cards, but currently i only have tin plated PCBs and for the controllers should be gold plated (since it has button contacts...)
  9. Bojan Pavsic

    Train automation - upgrading PF

    Since i'm very much involved in our LUGs displays, i have some experience in different Lego train technologies. There is 12V which is perfect for displays, but costs a little fortune and has some weaknesses with track contacts and pickups. Then there's 9V which is still used a lot in displays. There's quite some interesting options (ME rails, 9V motor repairs) but lacks the "control" of the 12V. And ofc, it's obsolete from TLGs point of view. Basicly if we wanted to go with the flow of time, we had to switch to PF. But a new problem came into view because we don't only display city/train dioramas. There's Technic too which messes up with the PF channels. After some thinking, tinkering and designing, we finally have a promising alternative for PF trains. I tried to keep everything very affordable and as small as possible and the result are a couple of modules that make our dioramas more interesting to the public (especially the kids) and have a lot more control. Let's cut to the chase... Some highlights: - The whole system works with RF (radio frequency) at 2.4 GHz. The frequency can be set from 2400 MHz to 2483 MHz in steps of 1 MHz (but can even go up into the 2500 area, so it doesn't interfere with WiFi & Bluetooth). They can be "hidden" inside creations, since they don't need the IR sensor to be in visible range. - RF transceivers (transmitter + receiver) are used, so 2-way communication is possible (thou not yet used, but there are some ideas). - Custom LiPo batteries that are smaller, can be recharged faster and have higher capacity then TLGs. - Multiple control options (tablet, phone, pc, ...) - Modular. First there is the IR receiver replacement (the little connector on the right side is for debugging & programming... isn't there in the final cards). It's a PCB with dimensions of 21 x 29mm (3 x 4 studs minus 1.5 mm on each side, if maybe there will be a 3x4 case made). It has a 3.3V voltage regulator, a 32 MHz micro controller (Atmel Xmega16D4), 3 status LEDs (1 is power, other 2 are for info / status / lightshow ). There's a connector for wire communication (I2C) and power supply. Another connector is for the communication card (currently it's a RFM73, but there will be an IR card too - for PF compatibility). It also features 3 headers for a "daughterboard". Let's call this module the "receiver". The second module is the driver card (it's an old picture, that doesn't have both driver chips and output connectors soldered yet). It is the "daughterboard" for the before mentioned receiver. It features two driver chips DRV8833 (same chip that's built in PF IR receiver V2), which makes it possible to control 4 motors (twice as much as the original PF receiver). It also has a power connector with separate pins for each driver chip (2x up to 3A power supply). A picture of both cards next to eachother. There will be different modules in the future: 10 LED channels for lighting or semaphores, 2 motors + 4 LEDs or servo + LEDs for track crossing or track switches. The third module is the "control" card which has 4 RJ45 connectors (network) with 6 input lines + power supply in each of them so 24 inputs all together. 4 boxes with buttons can be connected to it. They're ment to be put on the "keep away" fences in front of the displays. When a button is pressed, the microcontroller send the command to one of the receivers over the cable (for non-moveable motors like a windmill or anything that's not like a train) or over RF to a receiver inside a train. The command can be preprogrammed with a timer so it switches the motor off after let's say 30 seconds (That's a win-win because kids LOVE to press the buttons and check what they do, on the other hand the motors are not running the whole time of the show which lowers the battery usage & spares the motors). The "static" motor receivers use the PC ATX power supply (with DC-DC converters to lower the 12V down to 9V). The power supply part includes some LiPo cells (1200 mAh) with a 2S LiPo protection circuit. Dimensionwise it fits into an AAA battery box with half height (basicly it's a 4 x 8 x 2 block). Cells can be charged with 5C, discharged with 15C, so plently of power :) I'll switch the 2S PCM with some BMS (BatteryManagement) that will make it a "smart battery" with all the info that a phone or notebook battery has (cycles, temp, max. current etc..). It will be possible to notify the user when some battery will run out in a train etc... I made a usb stick with the RF transceiver too, so everything can be controlled and setup from a pc. WIP is a WiFi module with a web server that will be enable connections from any mobile device (notebook, tablet, phone) and control & setup everything. Another WIP that i'm currently working on is fitting the train engine receivers with a MPU9150 module (3-axis accel, 3-axis gyro, 3-axis compass) from which i'll try to get some usefull data about the x-y location (i hope i can get good enough data by using kalman filtering on the sensor data and correct the errors that will skyrocket after 2 integrations: accel -> velocity -> position). Here's where the 2-way link will come in handy because if the positioning will work as i hope, then there's a posibility of "auto-pilots" for trains, that will watch over the train compositions so they don't colide. Anyways... it's a WIP, just wanted to see if anyone has some additional ideas what could be useful to have in this system. p.s.: We have a display this weekend, i'll make some additional pictures from there (the system in action).
  10. I didn't find it any different on windows XP compared to windows 7, but i noticed that when i run LDD on onboard graphics (with advanced graphics on - visible bevels), LDD (or graphics) starts to "loose" icons in the palette and parts on the model (but only visually...). If i save the file, reopen LDD, everything is still there (again, for a while...). Tested on: - Intel HD3000 (notebook - i7 sandy bridge) - after a while, artifacts start to show up, stuff missing from the GUI etc... LDD sometimes crashes afterwards. - Intel HD4000 (desktop - i7 ivy bridge) - same as above - Ati Radeon HD3870 (desktop) - works fine - Ati Radeon HD7870 (desktop) - works fine - Geforce GT555M (notebook) - works fine I tried to turn off the advanced graphics on the in proc graphics (Intel HD) on notebook and desktop, which actually makes things work (no crashes, no "lost items"). My conclusion (from the couple of possibilities that i had the oportunity to test at home) is, that onboard (or in proc) graphics just don't cut it, when it comes to advanced shading models... Either buy a graphics card (no matter which, even a 20€ 4+ yrs old graphics card like 3870, is better then the built in graphics card in a 250-300€ processor), or use LDD without the shaders.
  11. Bojan Pavsic

    LDD hardware support

    A little update: I just bought: Desktop: - MB Asus Sabertooth Z77 - Intel Core i7 3770K - Corsair Vengeance 16GB cl9 - Gigabyte Radeon HD 7950 3GB WindForce 3x - PSU XFX Core Edition Pro 850W --------------------------------------------- Notebook (Dell XPS L702x): - Intel Core i7 2670 QM - Memory 8GB DDR3 - HDD 750 GB / 7200 - nVidia GeForce GT 555M 3GB - 17,3" @ 1920x1080 ---------------------------------------------- SSD: - OCZ Vertex 4 - 256 GB - OCZ Vertex 4 - 128 GB I'm gonna either put 128 GB SSD into the notebook additionally to the HDD and the 256 GB into the desktop or put the 256 GB SSD into the notebook and put the notebook HDD & 128 GB SSD into the desktop... Didn't really decide yet. For now i tried LDD on the notebook (and spent 3h figuring out why High quality rendering does't work until i found out the option to choose which graphics processor to use for a specific program - the internal i7 HD graphics or the nVidia...) and it looks great. LDD used all 8 threads at least some of the time, so i can confirm it is at least partly multithreaded. I opened my train station with 8k bricks on maxed out Advanced Shading and it worked flawlessly (on my old desktop i had like 1fps on min Advanced Shading with outlines). The sky scraper with 20k bricks works smooth too with min Advanced Shading (thou moving large parts "kills" the frame rate considerably - because of calculating connections...). This is with the built in HDD. I hope i have time time this weekend to install the SSDs, put the desktop together, reinstall windows on both etc...
  12. Bojan Pavsic

    LDD 4.2.5 Bugs

    About the impossible RL builds. It's not a bug. LDD doesn't really check that as it would be really hard to do (and take lots more processing power...). Everyone that uses LDD for planning knows exactly what's possible to build in real life and what not.
  13. Bojan Pavsic

    LDD hardware support

    As i wrote, i have a notebook (dell M6600 precision, i7 / 16 gb / ssd + hhd / Quadro 3000M 2GB graphics), but i don't have anything similar with a consumer graphics card to compare with, so i can't really tell if it's better or worse. Since LDD doesn't support multithreading, i7 or i5 doesn't really matter, but i need more thread capable processor for other things, so i7 is the clear winner. On my current desktop computer, i usually use LDD with advanced graphics on (edges on, lowest quality), unless the model gets over 2000 or so bricks. I do try to compensate with groups & hiding, but it's a bit annoying since LDD doesn't support unhiding specific group. My current desktop config is E7200, 2GB memory, RadeonHD 3870 512MB, wd velociraptor and it would work for some more time, but i'm getting problems that from time to time, graphics drivers "resets". Screen goes blank for 10-15 secs, then comes back with a message that "windows recovered from a graphics failure" or "graphics driver failure" or something similar. Everything works, except LDD. This happens like once in a week (the computer is 24/7 on). I lost quite some hours of LDD work because of that. Everyone will probably say it's the graphics card, but i'm pretty sure it's the mainboard, since i had problems with it from start (Windows 7 not working with my previous graphics card nvidia 7600GT), LDD problems in XP with my previous graphics card etc... It's a "combo" mainboard Asrock 4CoreDual-Sata2, it has AGP(8x) and PCI-E(4x) slot, DDR and DDR2 memory etc... I bought it to have a cheaper upgrade from P4 proc to core2duo, keeping my old DDR memory & AGP graphics. With time i switched the memory to DDR2 and graphics to PCI-E card, but there were always some problems... And now an opportunity opened to get a new pc (some freelance afternoon/weekend job, instead of getting payed, i'd get a computer), so i took it. Well, my point was, that on your computer, it's probably the memory that's holding LDD back. The usage gets to half gig quite fast and with you having only 1GB, it's probably the main bottleneck. I even noticed that i get to fill up my 2GB pretty fast. There was quite a big difference between LDD 3.x and 4.x (with all the new shaders and additional geometry data). It's time to move on anyways. I'll just probably wait for ivy bridge to come out and buy then. Might even be some changes on the SSD "market".
  14. Bojan Pavsic

    LDD hardware support

    @zinfinion Not really necessary... I wont overclock. Never did, never will, everything will be running at stock speed. I won't even think to bother with some extra cooling stuff. At one time i had a P4-3.0 prescott... It didn't even run with the stock cooler at stock speed and I had to buy some heatpipe cooling "tower" that was almost half kg in weight and basicly put a lot of stress on the motherboard. That was the first and last time i ever bothered with cooling so i don't really care about performance that much as long as it's rock solid. With that proc i even had to had the case opened all the time. So i guess i'll wait for ivy bridge procs to come out and get that. My primary goal is to have a working computer that i don't need to test for a day with prime95 or similiar running at full, just to see if it's stable enough under stress. @zinfinion Not really necessary... I wont overclock. Never did, never will, everything will be running at stock speed. I won't even think to bother with some extra cooling stuff. At one time i had a P4-3.0 prescott... It didn't even run with the stock cooler at stock speed and I had to buy some heatpipe cooling "tower" that was almost half kg in weight and basicly put a lot of stress on the motherboard. That was the first and last time i ever bothered with cooling so i don't really care about performance that much as long as it's rock solid. With that proc i even had to had the case opened all the time. So i guess i'll wait for ivy bridge procs to come out and get that. My primary goal is to have a working computer that i don't need to test for a day with prime95 or similiar running at full, just to see if it's stable enough under stress.
  15. Bojan Pavsic

    LDD hardware support

    @zinfinion Yea, you guessed it... I do some virtualization (i need to test software in different environments, so i tend to run 2 or 3 VMs in addition to host OS). So i7 2600 is final. I might even consider "scrapping" one monitor for a additional 250€ for the graphics to maybe get from 260 to 510€ for the card... I can always buy the third monitor later, changing the graphics is not that "easy". @superkalle Well, i have to buy a new one... have quite some problems with my current desktop pc.. I do have a Dell M6600 notebook which i use when the desktop doesn't want to cooperate, but i'd still like a desktop with multiple monitors.