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Everything posted by Shahriar

  1. Hi I can remind some times ago some one has written that it is better to replace 85'C Caps with 105C caps in old devices. (I think it was audioguru) Today, I was reading an article about SMPS troubleshooting. Look what a repair man has said: "(From: Jeroen H. Stessen ([email protected]) Electrolytic capacitors like to be kept cool! If there's anything that these capacitors can't stand, it's heat. It causes them to dry out. Electrolytic capacitors exist in (at least) two different temperature ratings: 85 C and 105 C. The latter are obviously more temperature resistant. Unfortunately they also tend to have a higher ESR than their 85 C counterparts. So in an application where the heat is due to I^2 * ESR dissipation, the 105 C type may actually be a *worse* choice! If the heat is due to a nearby hot heatsink then 105 C is indeed a better choice." Is it really true? ::) ThanX Shahriar
  2. Dear Audioguru A TV tuner is designed to receive a voltage around 400uV Upto 600uV From antenna. then how our body can produce a 6V signal. I think there are some other reasons in addition to electromagnetic in creating such big signal. shahriar
  3. Dear Audioguru 1- I Connect the Probe to an Antenna and a 50Hz signal appeared with pick voltage about 2V. 2- when I touched the antenna while it was connected to Probe a 2.2V 50Hz signal appeared. 3- when I touched the probe a 50Hz, 6V signal appeared 4- when I touched the probe a 50Hz, 5.7V signal appeared while I was standing over some papers. if it was all radiation so what is the roll of those papers, maybe If you examin it, find more useful things. ThanX Shahriar
  4. why when you touch Oscilloscope probe a 50Hz signal will appear? I think it should be related somehow to Earth connecttion. ThanX Shahriar
  5. Just tak a look at Datasheet, You will find what you need there. A mic is not always needed. Shahriar
  6. Look for ISD25XX Series. i.e. ISD2560 with 60second storage or ISD25120 with 120s. They have all things you need. i.e. Amplifer, Address Pins, ... You just connect a Mic. BTW, as I understood, the storage for all Ics are the same, the difference between 120s with 60s is in ADC Sample rate. In fact the quality of ISD120 is lower than ISD60. HTH - Shahriar
  7. Tell me if I got it. ;) The resistor will Dissipate power to remove the stored energy in Inductor. without Resistor it takes longer. I think for relays, because The resistance is high enough, they don't put this resistor but for an inductor which its Resistance is low, they put such Resistor. BTW, what was the name of this diode in English? I have forgot it. ThanX very much Shahriar
  8. Hi When an inductor is to be switched by a transistor, Usually a Diode is placed in parrarell with inductor to Protect Transitor from High voltage created with Inductor when Switch turns off. (I have forgotten the English name of this diode) But sth. a Resistor is placed in series with this diode? What is that resistor for and how to calculate it? ThanX in advance Shahriar
  9. Here another Useful link for IC 4510 - I think this is all you need. http://www.doctronics.co.uk/4510.htm Shahriar
  10. ِDear Herman For Counting down the UP/Down pin should taken low. if you want when counting is finished, the counter resets, you should connect the Max/Min output to Load Input via a NOT gate or a NPN transistor While all Outputs are pulled down via Appropriate Resistors (If IC doesn't have Internal Pull down Resistor, Check it). you can also use this Transistor to trigger your Buzzer or LED. If you want your Buzzer make sound for some seconds, you can build a Monostable by 555 and connect the buzzer to 555 output. I don't know if this is your Problem. ??? HTH - Sahriar
  11. You can Also build it with just a Microcontroller very simple and with lots of abilities. Of course building such circuits with TTL Ics is much more enjoyable. HTH - Shahriar
  12. Thank you Audioguru. ;) Do you know how can I determine the Saturation Current for My electromagnet with i.e. 200 turn 26 gauge wire. I do not have exact information about my core. it is just a piece of Iron. ThanX Shahriar
  13. Hi I want to know If I have an Electromagnet connected to a DC Voltage with a saturated Core, Can I pick up More heavy masses If I increase Current? or because the Core is saturated no difference will be? If I can, Then what is the difference between a Non-Saturated Core with a saturated core in this example... ThanX in advance Shahriar
  14. Hi Does anybody know the standard solution for detecting a fault in Lines to turn on a UPS before PCs reset. ThanX Shahriar
  15. Dear Ante Would you mind just telling me the sensor output voltage in two condition (PWM=1 & PWM=0) if we assume the Distance between The sensor and Electromagnet is constant (just approximate numbers). i.e If the distance is 2Cm the Vout = ??? when PWM =1 Vout = ??? When PWM =0 Dear Audioguru I don't think it is using such trick, the controller is just a Fan control. ThanX Shahriar
  16. Yeah, maybe buiding one is more cheaper. But I am just curioud about how this man have done this. The only part that I can't understand is: when the Electromagnet switches, will affect the Hall sensor. and everything goes wrong... can you explain. Here the file, I think you have seen it before a year ago Shahriar Levitation.pdf
  17. Hi I want to build a levitron by using a PWM IC (UC3843). I explain the PWM Controller behavior as below very simple to explain my problem. PWM=1 if VFB < 2.5V (Controller Vref) PWM=0 if VFB > 2.5V In most of Levitrons on the web, The sensor is placed near the ElectroMagnet. the ratiometric sensors output Voltage (Vout) is 2.5V when there is no magnetic field and Vout will Increase upto 4.2V or Decrease downto 1.2V depending on the magnetic field direction. and this is what I can't understand: When PWM is ON, the Vout (i.e.) will be 4.2V and absorb the levitron and Vout will Increase or decrease a little depending on the levitron magnet direction. if we add a Negative Offset voltage to Vout to bring it less down the controller Vref (2.5) to oblige the controller turn off, then when the electroMagnet turns off the Vout becomes a very low voltage and keep the Controller Off. (Vfb = Vout - Voffset) maybe I couln't explain it very good, to understand my problem try to imagin the Sensor output voltage in different figures when it is close to electroMagnet and PWM turns ON and OFF . Or In the link below, some one has opened a bought levitron device, can anyone explaine what happens to Sensors output when PWM is On and OFF http://hi.ece.olin.edu/icb/spring_04/ttgb/student/Ukiyo/gallery.htm ThanX in avance Shahriar
  18. Dear Audioguru Thank you very much... But do you have any oponion about The Transistor in the noninverting Pin. Have I explained it clear? ThanX Shahriar
  19. Hi I was reading an article about a Regulator and it was witten as below: "" Figure 1 combines low noise components and extra filtering to achieve an output noise floor of only 6 nV/Sqr(Hz). " Can Anybody tell me what does "nV/Sqr(Hz)" Mean! Of course the electronic Meaning, I know the meaning of nV or Sqr ;D ThanX Shahriar
  20. Dear windoze killa Thank you very much, Strange Abbreviation :) Dear Audioguru I Had the same oponion to mute the signal in the same manner as you said, Of course with a BJT. I thought if the signal has a DC (i.e. 3V) then it works but when there is no DC I didn't have any oponion for Negative Cycles of Signal. Because in this condition, the Base-Collector Junction would go in Forward bias. what would happen with a FET? 2- what I tested yesterday, In the Non-Inverting PAiA ciruit I attached, I put a NPN Transistor Between the 100k Resistor (R11) on the Noninverting pin of IC1:B and GND. When the Transistor was ON everything would work fine, when it goes Off, The Output would saturates gradually, but I didn't test it with a Sound Signal to see if It affect quality in Normal Condition. What do you think? ThanX Shahriar
  21. Dear windoze killa Can you write the full Dictation of CCT? I don't know what does it mean. Dear Audioguru Fading with a ramp was very tricky. But I didn't understood where you put that Resistor anf FET? ::) ::) to mute the system ThanX Shahriar
  22. Hi These two schematics are similar to the Ones I mean. One is a Single Supply Amp and the other is a double supply. ThanX in advance Shahriar Mute.zip
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