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Everything posted by Kain

  1. I figured it out. The trottle signal is only for speed control purposes. The motors normally spins in one direction only. Thus, if we want it working in reverse direction, the motor control has to be programmed with the corresponding instruction. Either way - it cannot be done on the fly with most RC brushless motor controls. Thanks for the help anyways. :)
  2. I want to build an H-Bridge with IGBTs since I got quite some here and I'll be switching about 15A. Now, the low side of the H-Bridge is easy to drive since potential that appears on the gate is basically the same as Vge assuming that I connected E directly to GND. However the high side is a problem. I read that I can get the required Vge there with MOSFET/IGBT driver chip or a pulse transformer. I would like to use the driver chip but I don't quite understand the connections to it. I looked at ST web and the chip I like is TD352. As looking at the datasheet: http://www.st.com/stonline/stappl/productcatalog/app?path=/comp/stcom/PcStComOnLineQuery.showresult&querytype=type=product$$view=table&querycriteria=RNP139=911.0 the way I understand it is that the Vh is 16V. However, is the GND the same as the GND on the picture or it is different? Basically as on the schematic here I am trying to pulse the Vcc which can be up to 80V, so I have 2 additional voltage levels - 16V and 5V with respect to GND up to 300mA used for control purposes. The IGBTs that I am using are IRGBC30MD2. Any suggestion is appreciated. ;D
  3. Um, reverse the connections? We are talking about brushless motor not brushed... I don't think this will have any effect on the direction of rotation. Maybe it's a software adjustment or something...
  4. Nice, but then how does one reverse direction?
  5. Wow, it's been a while since I visited the forum ;D, but anyways. I got my hands on a brushless DC motor as well as the controller for it and I wanted to use it for a non-RC model applications, so obviously in order to drive it I will need to emulate the same signal as the one a receiver is feeding to the motor control. I did some reading and what I figured is that the throttle signal is a pulse with anywhere between 1 to 2ms length and repeated usually every 20ms, in other words - it is a PWM that the servo is looking for. Now I am not RC maniac for now so if somebody is more experienced with this stuff can you tell me if the speed/direction is controlled by the pulse width only? Also are the motor controls looking for any other sequence besides the PWM signal? Any help is appreciated. By the way - I did a simple PWM setup with PIC which provides pulse width between about 1 to 2ms adjustable and repeats every 20ms. It consists of only 4 parts so if people are interested it can be added to the project section since it is as simple as it gets. :) Anyways, hope to get some answers on the question above. I know that Audioguru has always something to say (this is in a good way btw ;D).
  6. Somebody here asked about the parts that I used to build the PSU. I'm sorry that I respond quite late but I've been really busy lately with FPGAs... About the parts - Audioguru is right. I used the modified list for 5A. The power resistor is actually 15W and it's mounted on the PSU case. Smaller one will do as long as you can keep it cool under load. The large capacitor on the input is 20000uF in my case. I used 2x10000uF since it was way cheaper to get those insead of aiming at 20000uF/63V. The transformers that I used are from Hammond 30V @ 7.5A toroidals. In other words, there is no change in the part list. I bought most of the parts from Mouser, with the exception of the transformers which came from Digikey. Hope this helps. :)
  7. Hi Zombie! I hope you don't mind pasting the URL ;D
  8. Ok, it seems nobody knows anything about it at this point. I checked things myself and it comes down to the point that USB to LPT can be used only for specific purpose of printing and it is not guaranteed to work with all printers either. In other words if one needs to expand a newer PC with LPT he will need PCI-to-LPT card or PCMCIA-to-LPT since they are supporting the full achitecture of LPT and it's functionality. While PCI cards are cheap (11-20USD) I cannot say the same for PCMCIA - about 90USD before shipping and tax... In other words if you have a new PC or plan to buy one and have no access to one with LPT, just stay away from LPT and you will save yourself the headache...
  9. Ok, so what you meant is that the driver chip is switching on and off the IGBT/MOSFET more efficiently as well as providing for "dead time" when reversing directions. Would you recommend any IC in your experience? Thanks again ;D
  10. Thanks Audioguru! Can you schematically show what you mean by saying that one MOSFET is connected to the other? I thought that they need to be both "on" if they are to conduct the current through the motor
  11. I just received my FPGA board from Digilent and besides the fact that it looks nice I noticed something that I don't like at all - it came with LPT programming cable. Well LPT is a dying standard as we can all see - new PCs or laptops don't even have one anymore and this is my case, as well. The USB programming cable is $40+ with the shipping and I don't think that this is reasonable at all given the fact the board was about $100. So my question is: Would a USB to LPT adaptor work well in this sort of aplication or not, and which one would you recommend? I quick glance over google showed me average prices of $10 to $12 which is obviously way cheaper than the cable offered by Digilent; not to mention that USB-to-LPT can be used for many devices in case one ever needs support for other LPT devices...
  12. Ok that sounds bad now. So virtually I have to describe all situations where don't cares will normally simplify the situation... That just made my code close to 4000 lines... :'(
  13. I am really curious if EPROMs or EEPROMs allow for "don't care" conditions. Any ideas?
  14. Thanks MP. I got them in friday afternoon so everything is alright now ;D
  15. Has somebody here ever ordered samples from Linear Technology? I ordered few chips from them and I got confirmation on my e-mail but nothing in the mailbox yet. It has been a week. Maybe I'm not patient enough, eh? ;D
  16. Thank you both Audioguru and Ante, and Ante you are right - I did put quite some time into it. I love the results though ;D
  17. Ok, here are pictures of the completed PSU. It is now set at 12V on both sides as one can see on the picture. The fan on the top cover is pushing air in the case causing circulation. The air gets out from both sides - left and right as it cools down both h/s. The fan is actually temperature controlled - it senses the temperature of each of the h/s... The PSU also starts up with a delay - I am passing the start up inrush current through a resistor in series to limit it down otherwise the fuses blow up. That is pretty much all. The info about ripple and so on I already posted. I'm happy the project is finally finished
  18. Alrighty, I assembled the machine and it is fully operational now. The unit was tested again 3 days ago in my university and the results were more than satisfying - ripple under 6A load was merely 2mV and I am not sure if that wasn't partually scope noise. On any other working modes the ripple is less than 1mV. The maximum current I got out of it with dead short output was 6.97A. I will take few pics soon and post them too since I put the effort not to only get it to work well but to look well too. People in school nearly freaked out when I got to 6A without problem, and it is not surprise given the fact that the lab PSU's that we use are limited to 1.5A
  19. Happy Birthday Ante. Thank you for helping us all in here. I hope you had a good one, or are still haiving it
  20. I have already tryed this, and it does not help. In fact this behavior persists even if I have no probe connected at all...
  21. Well, so far I have only used it in home and my boss's place and it acts in the same way in either place. I haven't really dig the ground and put some salty water to kill anything that I get my hands on ;D but given that I have used it on 2 different places and it acts in the same way should tell me something I think. Do you think that I should try to make myself guaranteed good ground to make sure that grounding is not the problem?
  22. Do I get this right or there is no place arround here? I checked for few services but they are all online... and I don't exactly like the idea of shipping the scope to a company , especially outside of CA. C'mon people, if you don't know a place at least say "I don't know"
  23. I was just having fun with the PSU from: http://www.electronics-lab.com/forum/index.php?topic=196.0 and tryed to measure the ripple again. Well I noticed something that I didn't pay attention to before - the scope is actually measuring some p-to-p voltage of about 200mV when used on 5V scale without me feeding any signal in. When i go for 10X probe it goes 800mV without me feeding any input signal. Now, I tryed to read the signal by playing with the trigger but I cannot lock down on anything and on top of that these readings are persistand on all time bases. I haven't had too much experience with scopes, but I am guessing that a calibration is needed. Does anybody in the forum know of a good and cheap
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