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???
07/07/09 10:46
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 		 #166834 - Please clarify
Responding to: ???'s previous message
Sivanand Somasundaram said:
YEs I understand that there needs to be a resitor for each diode.
BUt since my present bread board was small to make quick connections i used only leds in two pin lines and rest of them i did not use any led or resitor.I directly measured the voltage from the pin.
I will check again tomorrow if there is still the problem of 2.7V

1) The voltage will not magically change.

2) In an earlier post, you wrote "I finally connected 8 leds to my port 2 which is my output port". That definitely sounds like 8 diodes.

3) You have still not mentioned what resistance value on the resistors you are using.

List of 137 messages in thread
TopicAuthorDate
debugging AT89S52            01/01/70 00:00      
   where?            01/01/70 00:00      
   FAQs            01/01/70 00:00      
   Image uploaded and other corrections made            01/01/70 00:00      
      You MUST use a max232 or equivalent            01/01/70 00:00      
         MAx232 connections            01/01/70 00:00      
            if you have connected the PC RS232 directly            01/01/70 00:00      
            ambiguous?            01/01/70 00:00      
         Not necessarily!            01/01/70 00:00      
   Image of MAx232 connection for reference            01/01/70 00:00      
      89S52 - PC -> MAX232 conenctions            01/01/70 00:00      
         max 232 connection            01/01/70 00:00      
            To test MAX232            01/01/70 00:00      
               Testing a Com port using hyperterminal            01/01/70 00:00      
                  PC Loop-back            01/01/70 00:00      
                     Connections of COm port            01/01/70 00:00      
                        So what about direct on the COM port            01/01/70 00:00      
                        Check the PC's driver            01/01/70 00:00      
                           Testing an RS232 driver            01/01/70 00:00      
                              results of rs232 testing            01/01/70 00:00      
                                 Hyperterminal            01/01/70 00:00      
                                    data not displayed in echo mode in hyperterminal            01/01/70 00:00      
                                       Why do you call it hypoterminal?            01/01/70 00:00      
            I got confused regarding the value of capacitors            01/01/70 00:00      
   MAx driver and hypertermianl problem solved but...            01/01/70 00:00      
      can somebosy please reply?            01/01/70 00:00      
         Try a step by step aproach            01/01/70 00:00      
            Reg Step by step approach            01/01/70 00:00      
               How are you programming the flash memory of AT89S52            01/01/70 00:00      
                  clarifications            01/01/70 00:00      
                     Not to UART            01/01/70 00:00      
                        Additional info about the board AT89S52 and ISP            01/01/70 00:00      
                           Many issues solved but one            01/01/70 00:00      
                              How?            01/01/70 00:00      
                                 diode...connection            01/01/70 00:00      
                                    Explain with graph or text            01/01/70 00:00      
                                       clarification            01/01/70 00:00      
                                          Study the AT89S52 datasheets            01/01/70 00:00      
                                          Please read the answers you get            01/01/70 00:00      
                                             It works now!!!!            01/01/70 00:00      
                                                What series resistor?            01/01/70 00:00      
                                                   Connection of diode            01/01/70 00:00      
                                                      Please clarify            01/01/70 00:00      
                                                      the problem is NOT the 2.7V            01/01/70 00:00      
                                                         clarifications            01/01/70 00:00      
                                                            Google Ohms law            01/01/70 00:00      
                                                               Report            01/01/70 00:00      
                                                                  Measure pin voltage when held low, not hgh            01/01/70 00:00      
                                                                     trouble again            01/01/70 00:00      
                                                                        details...            01/01/70 00:00      
                                                                           Troll?            01/01/70 00:00      
                                                                              clarification            01/01/70 00:00      
                                                                                 I am not an electrical engineer I am a mechanical engineer            01/01/70 00:00      
                                                                           Do not accept everything as is, Revise your schematic            01/01/70 00:00      
                                                                              who cares?            01/01/70 00:00      
                                                                                 Short-circuit            01/01/70 00:00      
                                                                                    OOPS, anyhow            01/01/70 00:00      
                                                                              circuit revised but ....            01/01/70 00:00      
                                                                                 have changed to new buffers ..            01/01/70 00:00      
                                                                                 Post the revised schematic to check            01/01/70 00:00      
                                                                                    schematic            01/01/70 00:00      
                                                                                       there are "LED resistors" whwre are the LEDs and            01/01/70 00:00      
                                                                                          you are in deep waters            01/01/70 00:00      
                                                                                          what's the error?            01/01/70 00:00      
                                                                                       It is hopeless, but anyhow            01/01/70 00:00      
                                                                                          Vf for diode            01/01/70 00:00      
                                                                                             Too deep waters indeed, describe everything            01/01/70 00:00      
                                                                                             then how do you propose they will both work when in patralle            01/01/70 00:00      
                                                                                                Haven't you seen that he has series resistors with each LED?            01/01/70 00:00      
                                                                                                   update            01/01/70 00:00      
                                                                                                      Resistor value            01/01/70 00:00      
                                                                                                         update.-2            01/01/70 00:00      
                                                                                                            free-wheel diode            01/01/70 00:00      
                                                                                                               details of relay            01/01/70 00:00      
                                                                                                                  details of relay-2            01/01/70 00:00      
                                                                                                                     free-wheel diode always reversed            01/01/70 00:00      
                                                                                                                  No simple diode but a zener in series!            01/01/70 00:00      
                                                                                                                     zener and IN4148 already in series?            01/01/70 00:00      
                                                                                                                        clarification            01/01/70 00:00      
                                                                                                                        The datasheet is a bit confusing...            01/01/70 00:00      
                                                                                                                           no space to connect            01/01/70 00:00      
                                                                                                                              Solder it on the solder side!            01/01/70 00:00      
                                                                                                                                 Thanks..but            01/01/70 00:00      
                                                                                                                              Did you made a PCB ?            01/01/70 00:00      
                                                                                                                                 YEs true            01/01/70 00:00      
                                                                                                                                    Regarding zener and In4148            01/01/70 00:00      
                                                                                                                                       update on relay testing            01/01/70 00:00      
                                                                                                                                          testing relay using multimeter            01/01/70 00:00      
                                                                                                                                    NO, NO, NO            01/01/70 00:00      
                                                                                                                                 as opposed to            01/01/70 00:00      
                                                                                                   what about the coil across the LEDs?            01/01/70 00:00      
                                                                                                      full picture of relay            01/01/70 00:00      
                                                                                                         use preview            01/01/70 00:00      
                                                                                                            true            01/01/70 00:00      
                                                                                                      Heaven, Erik, ...            01/01/70 00:00      
                                                                                                         it works but for relay orientation            01/01/70 00:00      
                                                                                                            Look at this, too            01/01/70 00:00      
                                                                                                               latest posts            01/01/70 00:00      
                                                                                                                  Don't be so quick to experiment            01/01/70 00:00      
                                                                                                                     clarifications            01/01/70 00:00      
                                                                                                                        make simple tests like this            01/01/70 00:00      
                                                                                                                           reg the test circuit..            01/01/70 00:00      
                                                                                                                              circuit details            01/01/70 00:00      
                                                                                                                                 Still experimenting            01/01/70 00:00      
                                                                                                                              Already covered in this thread - more than once            01/01/70 00:00      
                                                                                                                                 but how did the above circuit work?            01/01/70 00:00      
                                                                                                                                    Experiments can work, even if incorrect            01/01/70 00:00      
                                                                                                                                       there is no zener diode            01/01/70 00:00      
                                                                                                                                          Don't ignore the datasheet.            01/01/70 00:00      
                                                                                                                                             thanks            01/01/70 00:00      
                                                                                                                                          Forget the sales engineer!            01/01/70 00:00      
                                                                                                                                             Minimum turn-on voltage            01/01/70 00:00      
                                                                                                                                    it HAPPENS to            01/01/70 00:00      
                                                                                                                                       ther is no other way now            01/01/70 00:00      
                                                                                                                                          where there is a will, there is a way            01/01/70 00:00      
                                                                                                                                             is this what you are suggesting?            01/01/70 00:00      
                                                                                                                                             Relay            01/01/70 00:00      
                                                                                                                                                Finally reached the shore            01/01/70 00:00      
                                                                                                                                                   Project completed ?            01/01/70 00:00      
                                                                                                                                                      yes completed            01/01/70 00:00      
                                                                                                                                                         Good luck!            01/01/70 00:00      
                                                                                                                                                            Reagrding other relays            01/01/70 00:00      
                                                                                                                                                               Scan through catalogs            01/01/70 00:00      
                                                                                                                                                               you do not need to buy there, but            01/01/70 00:00      
                                                                                                                                                                  form factor            01/01/70 00:00      
                                                                                                                                                                     The datasheets normally have the answer            01/01/70 00:00      
                                                                                                                                                                        files            01/01/70 00:00      
                                                                                                                                                                           Not so many files            01/01/70 00:00      
                                                                                                                                                                              Regarding LEd            01/01/70 00:00      
                                                                                                                                                                                 _always_ current-limited supply!            01/01/70 00:00      
                                                                                                                                                                                 Only if it contains a current limiting resistor!            01/01/70 00:00      
                                                                                                                                                                                    thanks and file updates            01/01/70 00:00      
                                                                                                                                                                                       You can enormously save user space...            01/01/70 00:00      
                                                                                                                                                                                          Hard now            01/01/70 00:00      
                                                                                                                                                                                             Correct!            01/01/70 00:00      
                                                                                                                        never do that            01/01/70 00:00      
                                                                                                         Kai, you must be able to see invisible ink            01/01/70 00:00      

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