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Kain

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Everything posted by Kain

  1. Here we go. Hopefully this is final ;D PSU_revised.pdf
  2. Ok. That sounds bad now since I will end up redoing the board. Before doing so please check this schematic that I am posting now where I applied the recommended changes. I want to be sure that this is correct since dealing with that small dual layer PCB isn't exactly that easy (meaning it takes more time) and I don't want to redo it too many times 8) Schematic.pdf
  3. Ok guys. It seems that nobody is feeling like working enough to check the board I just posted. Well you better check other people's job if you plan to use it because I messed it up a bit - the footprint for the op amps was kind a wrong - distance between pins was way too high so I had to correct this. It's good at least that I checked it ;D. The one I'm posting now is all good. I also made little corrections so whenever you have a bridge from one layer to the other it has larger pads 8). Have fun, and please check it again PSU.pdf
  4. I believe you can try to add a simple transistor based switch to do this for you. You should place it so it will shunt the 2.2K pull down resistor of the monovibrator. Its base should be connected to RC circuit to time a short interval when you power up the circuit. What is the power supply that you use though? I mean is the output voltage is well filtered because this might be one of the main causes for this strange behavior :( I see a filter capacitor is missing in your circuit, so you are totally relying on the stability of the DC power supply. It won't hurt you if you put 100uF and few nF capacitors to filter the voltage no matter if you think that the PSU is good or not. Just my oppinion :)
  5. Well I didn't say that there is anything wrong with using good old fashioned UV tubes, but this doesn't answer the question. Thanks for the suggestion anyways :). Since it seems nobody had tryed it (no answers to the topic) I decided to try it myself. I got one UV LED from the local electronics store. They told me it's high intensity, and I can actually see it is when I feed it with 3.5V at 30mA. I don't know what is the rating of this LED but I know I've seen more powerful than those. It is extremely irritating to eyes as well - I can look at it for no longer than 2 sec and this is not looking stright in the lense - I don't advise you to do so anyways ;D. Anyways, I tryed the exposure and I exposed precoated board for 5 min. Worked just fine. The distance that illuminated from was about 150mm for I can get more uniform patern over the board as well as illuminate larger area. I'm looking for a way to distribute the light more evenly now using more LEDs. Any ideas how I can spread the LED's beam uniformly, or close to uniformly since I plan to use more than 1 LED? :)
  6. Alrighty. In case somebody is interested in the results, besides me of course ;D, here you go. I exposed precoated board under white LED's light for 10 min. The LEDs are rated 10000mCD so they are not exactly weak. I placed the board right infront of the lenses for maximum illumination and still it did not get exposed - it did't develope even slightly. Then I exposed half of this same board to regular luminiscent lamp and this half developed right away. In conclusion, if you guys want to work under light - to cut precoated boards, to make the coating and so on I believe high intensity white LEDs are the right solution before lamps. First, it's white light meaning you would be able to see bettter under white light than monochromic red for example; LEDs are way more energy efficient, and LEDs have way longer life on average. The only disadvantage is the required low V. Time to build myself a lamp now ;D
  7. Well this is a good idea about the boards and the wires. I think I will use photo-exposure on a large sheet so there will be probly about 5 boards per sheet or so - I need to calculate. I still have one question though - the main power nets I did with width of 3mm. Since I lost my chart I was hoping if somebody can tell me if this is enough to take 5A at 30V? If this is fine then I believe the design should be good. :)
  8. Oh well, it seems I will need to do trial and error - I have few high intensity white LEDs so I'll expose little piece to see how it goes 8)
  9. Alrighty. Here is the double sided PCB for the project as I promised. It took me a while - I have other things to do too you know ;D. I included the separated Top, Bottom layers - they are all ready for print meaning you don't need to mirror anything. The only thing you will need to do is scale them corectly. I would scale them by the IC pins - they are very good indicator if you have scaled correctly. When you print out both layers on separate paper when you put both printed sides toward each other, the vias should match. I included the schematic, the component guide as well as the view of the board when both layers are matched as I said before. If somebody please can check if I didn't mess up the schematic since there have been too many posts here about the mods to this project. Keep in mind that the 50000uF cap and the 15W resistor are off the board. There are vias for them but they will be mounted off board. If you find any errors please let me know. I'll be doing this one myself soon ;D PSU_5A.pdf
  10. Well, if you check on ebay you can find pretty good deal - 100 UV LEDs for less than 10$ in total. I think this is more than cheap ;D. By the way, please if you know something about using UV LEDs for photo-exposure please post on: http://www.electronics-lab.com/forum/index.php?board=13;action=display;threadid=2406 :)
  11. Good to know. I think I read few days ago about different processes of making white LEDs and one was actually by combining RGB by adding dots of different compounds on phosphorus to make all 3 colors, thus white, but anyways. The main question is still would it be possible to work under this light without trashing the board? I would check on the datasheet though. Thank you anyways audioguru 8)
  12. When using the photo-exposure method to transfer the artwork, we all know that it has to be perfectly alligned especially if we are making double layer boards. Since this cannot be done under regular light as we all know, I wonder if it can be done under light emmited from white LEDs? The reason why I am guessing it might work is because they are basically RBG LEDs all in one, but they do not emmit UV which is needed for the board to be exposed. Any suggestions?
  13. Recently I was using the photo-exposure method to do some boards (I like the tonner transfer but sometimes I need to get more acurate ;D). I used my friend's exposure room to do it - he's having some huge lamps which emmit 75% light in the UV spectrum. However, I've seen that there are UV LEDs available on the market, and it's been a while. Actually when I checked on different manifactors it seems that there are high intensity UV LEDs now, so I wonder if a small exposure box can be built using those? The wave-lenght of most types is arround 380~400nm with power rating 80mW. Some have even 3000mCD rating but this is kind a not right since UV light is not visible. Anyways, do you think that this would be enough to expose a board well enough?
  14. Dazza, I almost got you though, huh? ;D Just kidding. The blow off thing hasn't happened to me before but for I always use resistor to limit the curent down as audioguru suggested. Audioguru, doesn't the current protection limit the current down so it will serve the same purpose as resistor in this case?
  15. Dazza, I think the application you are talking about can be achieved pretty easy - I mean the self turn off. In fact, you almost have it built in already ;D. If you noticed the LED that is used for indication would light up if the current limiter is working. However, as far as I understand the current is still there, but cannot exceed the given value. So, if you battery is the load in the circuit, while it's being charged it would become lighter load thus the circuit protection would stop working and the LED would turn off. If you invert this signal for the LED you can have a circuit that goes on when the LED turns off, such as something that breaks the circuit and so on, such as thyristor in combination with reley or something else. Use your imagination ;D. If I am right your shut off is as easy adjustable as the curent limiting is. I hope I'm right thoough hehe
  16. Yup. The resistor I will be using will be the one i posted about earlier - aluminium cased with small fins as you said.
  17. I would use 2 monting bolts x 3mm so this is not a big deal. The real thing is that I took the 15W resistor off the board - it will be way better if it's attached on the box and link with short wires to the board since it will allow it to cool better i believe. This is why the board can be that small ;D
  18. Ok, since nobody posted any PCB for this project, I decided to finish the job. The board I have worked on so far would be double layer board since I was trying to make it smaller, I really hope you don't mind. I can do single layer too but it would be about the same size as the original. The one I am about to finish is 100/60 mm.
  19. I guess many people in this forum would like to use sometimes less space for PCB in their projects meaning that they will be trying to achieve higher PCB density. Sometimes it works with very good placement of the components, but I noticed that even if this is the case most components have to be horizontally placed; therefore they will be still taking more space than needed for many projects. I encountered this problem few times already, so I wonder if there is any good way, or nearly perfect way to create double sided PCB since this definately allows for high density PCB. The hardest part to me seems the allignment of both layers since the rest is basically done by the PCB server of the software that people use. There is an article about allignment for 2 layers that I haven't tryed yet: http://www.robotroom.com/PCB2.html Please if you have some experience or knowledge on this topic share it :)
  20. Ante, I've been thinking about this but it's kind of pointless to put water cooling system considering that the air cooling h/s with large enough surface area would do it fine. I have built water cooling for my PC though, but the reason is overclock, noise and staility. It has been working for 1.5 years so far with no leaks and problems (crosses fingers). About the immortality of the project - if I make a water cooled setup and it happens to leak somewhere it will be extremely mortal ;D Oh, btw here is a picture of the front pannel of my PSU - almost finished. Only the writings and knobs for the potentiometers are missing :)
  21. I have built dual output 3A PSU - the original chematic. When not used on extremas it's ok. Now that I'm trying to build the 5A PSU I need really large heatsinks since I want it to be as stable as possible. Now the trouble is that this kind of heatsinks aren't easy to find. I was planning to use 2 of those instead on 2 walls of the box, so basically those h/s will be as part of the box. I'm interested in 2 flat h/s sized 150x250mm or more. Any suggestions where I could purchase something similar or same? I live in California, US btw. If samples are available from somewhere I would really appreciate it ;D
  22. Yes they do use LASER for speed measuring. My friend found out in the hard way while crusing at 200+ mi/h ;D
  23. It looks nice. Any idea where I can get it from and on what price? By the way is this 10W or 15W on the picture?
  24. I was just making some libraries for the PCB of this project when I saw the "small" power rating of R7 - "only" 15W. Now, I was checking on different manufactors about this type of resistors since they are not something that I can get here in some local store. This is what I saw in mouser electronics: http://www.mouser.com/index.cfm?&handler=data.listcategory&terms=71-RH25-0.27&Ntt=*71RH250.27*&Ns=MfgrPartNumber%7c%7cSField&N=100+61300000&crc=true I know this is 25W instead of 15W, but this seems to be one of the resistors that has R = 0.27. The thing I do not like about it is that it's low tolerance resistor which adds up to the price even more as you can see. What I like about it is that it is basically built into a heatsink ;D. I am just looking for appropriate resistor so I can finish the library and PCB. I was thinking also of more than one resistors in parallel, but I don't think this will save neither space or money. Any suggestions?
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