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Everything posted by bogdan

  1. what i want is to use a receiver and emitter..... i can't find those transcievers around here.
  2. my mainboard has a IR/CIR connector on it, so i want to connect an emitter receiver to it. the pinout on the connector is: for IR: VCC5 key IR-RX GND IRTX VCC and for the CIR: VCC5 stand by x CIR-RX GND x x i assume that x means not connected. if anybody can help, i need to make an IR interface for my cell-phone.
  3. well, keep looking for that schematic.... i really want to try it... also, you know anything about generating power from a pletier moddule by heating it with a candle?
  4. Hearse, the first circuit is missing the current limiting resistor for the led. the second has a bit of a problem... for the second, i would increase the 220 ohm resistors...maybe to 560 .... i find the LM3909 unsiutable and expensive for this application. it is good for places where you want to power a led from 1.5V(a single battery) for this application a 555 is best, or probably a 556 if you want them to flash with 2 different rates. you could also add some transistors and make put together more red leds and more green leds.
  5. Siddhu, this is what i have seen on tv some time ago, yet i didn't catch too much. do you know any website?
  6. when a quartz cristal is swueezed it produces some electricity. has anyone thought to use this for charging something? or maybe use this electricity to power something? these kind of things are used in lighters and other stuff. has anyone actually built this???
  7. the schematic with only the zenner and without the transistor can not suply you too much current. a 1.3W zenner cand suply a few miliamps(sorry, no time to do the numbers). if you want 5V, you might consider using a 5.1V zenner in place of the 4.7V one.
  8. since you are using 4 diodes, this forms a full bridge rectifier. so you need to power your circuit from 0 and 12V. you could use 0 as ground and use 2 diodes, one from each 12V connection and you get a full wave rectifier also. here is what i mean... the 2 circuits show the 2 ways you cand do the rectifying. from the cap you connect the regulator and other components.
  9. well, i have seen something like this. you produce an ultrasound and modulate it in such a way that the human ear will hear as the sounds were at the correct frequency. since you can make the ultrasound unidirectional, i think that this is the sollution. still, making the sound perfectly directional is not possible since it is transmitted trough the air, so the nearby air vibrates along with the sound column and so the sound is transmitted in various directions, with lower intensity of course.
  10. well, i meant to say that the circuit should work for 2 to 5V, and produce enough voltage for the led to light up in the same way, no matter the input voltage. so any suggestions?
  11. well, do you know any common driver, because here components are quite hard to find, so i need something common. maybe some other suggestions?
  12. i found this simple PWM for motor control. it is something usefull, and i was thinking to build it and wanted to know what others think. maybe some of you know a similar circuit, i mean, simple, but maybe more performant? here is the circuit: http://www.geocities.com/tjacodesign/motor/motor.html
  13. anyone cand suggest a led driver chip? one that requires few external components? it should be able to drive 1-2 white leds from a suply voltage like 2-5V....any ideas?
  14. one thing i have thought of would be to use a super cap and some rechargable batteries, and a led driver. this way you could charge the cap, adn also the batteries. the batteries will last longer than the cap. you oculd also add a solar cell to charge it from light. an interesting idea would be to create a rechargable flashlight that can get energy from various forms...like shaking, light, heat(?! maybe it would be possible?) and some other stuff.....so it would be some sort of universal powert flashlight.... i have thought of this, but i don't have the time now to try and experiment some ideas. one way would be to make something really small and light to be very portable....
  15. now, you are now allowed to use a regulator chip.... but what about using a switching chip, with some extra components????? or building a switching with descrete components? if you can use a simple circuit with a zenner and a transistor. mixos, if you look at the second circuit you have posted at a connection called 'sense' you will see that all the resistors connected at the bottom right of the schematic are actually shorted....so.....why are they there?
  16. i think that the best way is to use the original load to mesure, or a load of the same impedance. if you put the original speaker to the output, then you have the corrrect results. now, second problem. if you power the amp from your car, then the voltage output is likely to be 12-14V. if you use the sound card to mesure, then if i am not mistaking the card olny accepts max. 5V input. considering that you have 12V, you should divide this voltage with a voltage divider, so you have a smaller voltage. i think that the best way you can divide the voltage is to divide it to 3. this way, the max voltage it can handle is 15V, and it is easier to do the calculations. the best way is to use 3 identical resistors, say 1Kohm. put them all in series and connect them in paralel with the speaker. then use as input the voltage across the resistor that is connected to the ground. now, here there comes a grounding problem. if you will power then amp from a suply that it is plugged in, then it should have the ground connected to the mains safety ground. the computer also has the ground connected to the mains safety ground. now, the speakers may connect between the ground of the amp and the output of the amp, or the speaker is connected to 2 outputs of the amp. in this case, if you try to mesure the THD you will short one output of the amp to ground. so this is why it is important to know wich wire coming from the speaker is the ground. if you cannot test the amp with the original speaker, then use a resistor with the same resistance as the speaker, but remember that is must be able to handle the power that comes from the amp, in this case you could use a 20W resistor. yet, the best result comes with the exact load you will use for the amp, the same speaker.
  17. well, a bridge is better than 4 diodes, because it cools easier. this is because the surface of the birdge is highter than the one of the 4 diodes(maybe .....?!) and buying a 10A bridge is cheaper and uses less space than 4 diodes. now a switching mode suply could be done with about the same costs, but i am going off topic, since we want to modiy the original suply.
  18. i'm glad you sortoed this out and your circuit works. can you post a picture of what you have buid? i would really much apreciate if you do so!
  19. so................... ??? ??? isn't anyone still inerested in modifying the suply? ???
  20. a good thing would be to create a SMD version of the circuit. maybe find a beeping cheychain, take it's guts out and put this in.
  21. i don't really know what the problem is. but the error should not occur in winME or 98. it is an XP problem. i does not allow direct usage of the port.
  22. just a suggestion. if you cannot find a 2 x 12v transfoermer, you could use a power suply made from 2 LM317 regs in series. though, the maximum output voltage is a bit lower. i think that having that switch is the best way. also, if you could use a 3A or 5A bridge, then you will have less power lost on the bridge. Pinky, 24*1.4=33.6, but you forgot about the loss on the birdge. thats why i suggest to use a 5A bridge. you loose less on it, since it has a lower dropout voltage. you could use a 4700uF cap for the filtering of the rectified ac. this means lower ripple voltage. and don't forget about the minimum load resistance. you could use a 120R resistor as suggested, but at 30V you have 7.5W disipated on it, not very good. i think that a single LED with a resistor in series is enough. and add a 5K resistor at the output too.
  23. CDAK, why don't you try to reduce the gain for the LM387? LM386 is a power amp, not really good to replace all the 741 amps with 386, maybe just the last one, to get a stronger output. t_ang4, what are you powering the circuit from? maybe you have suply noise? also, maybe you hgave a problem with the caps? if they are leaking then this should be the problem. you might try to replace the cap from the mic with another and see... also, i had experience with a lot of noisy electret microphones. why don't you try another thing for input? maybe use a speaker(though not so good). also, you should try to connect the input of the first op-amp to ground and see if without the mic you still get the noise.
  24. i have a suggestion. putting the plates closer togther increases the capcity, wich is small when using water as dielectric. also, i suggest that when insulating the plates, use something wich has a high relative permitivity. this means that you will have a big difference between the 2 capacitances. why not use thick insulated wire from a transformer?
  25. here is something nice........... http://www.newscientist.com/news/news.jsp?id=ns99992123
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