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  1. K

    [SOLVED] need help in figuring our the LED frequency

    so, i simply connected a LED (forward voltage of 3.3v) with a series resistor (85 ohm), that should give 20mA of current to the LED. - then , connected the frequency generator to the series circuit, the LED worked pretty good at about 900kHz .. but when i kept to 10Mhz or more than 3-4 Mhz...
  2. K

    [SOLVED] comparator maximum frequency help.............................

    what is the maximum frequency that Lm239/339/239A comparator can operate on ????
  3. K

    relation between bps and frequency

    If i sending 9600bps ..how to approximate what frequency it is ? - lets say if i am giving 10kHz square wave....--> what Bps it is ?for 10khz frequency how many bits i can send per second at max? - on the other thread i saw 1Hz is 2bits... so 10kHz is 20kbps ???
  4. K


    I gave square across LED but the the photodiode diode detects sawtooth waveform.. which is clearly not a square wave,,why is that >??
  5. K

    [SOLVED] transistor gain calculation

    I have seen a lot of calculations where they take GAIN as 10 or 20 instead of the original value in the datasheet.For example 2n2222 transistor VCC = 5 ,Led(Vf = 3v). For Ic = 20mA,Rc = [VCC-VF(LED)-VCE(SAT)]/Ic = [5-3-0.25]/20mA = 87 ohms. Ib=Ic/Gain = 20mA/110 = 0.18mA Rb = [Vcc-Vbe]/Ib =...
  6. K

    [SOLVED] basic current measurement value through LED

    i designed a basic circuit as in the picture.When i given the voltage from voltage regulator.The measured current through LED is same as the simulation = 12.7mA. but when i connected to the Frequency generator(10kHz with DC OFFSET of 5V), the current through the LED is double the value ??why is...
  7. K

    need help Plotting 3D graph in matlab with x,y,z axis ...................

    i want to plot a 3 dimensional graph. x-axis 1 2 3 4 5 y-axis 10cm 20cm 30cm 40cm 50cm z-axis 0.5 0.6 0.7 0.8 1 3 these are my values,i cannot able to plot these in 3D .. it was easy with x and y but i am not able to place z-axis..is htere any equation i should place ?
  8. K

    conversion of unit values

    how to convert lux to dbm conversion. i am measuring light using photometer,the distance is 50cm. for 1088 lux..how to convert it to power ?
  9. K

    [SOLVED] Picture encode/decode

    is there any software that decodes a picture into codes (html,c,c++ ) and encodes it back ? - operation should be... 1)upload a picture in the terminal 2)get the code language 3)paste the code language again 4)extract the picture from the coding.
  10. K

    [SOLVED] Help with the information how to built the circuit.

    I have a chip (SN75451B).I am trying to understand the function of it so that i can built a circuit which shows the function of it.how to test it?i mean i want to give a Square wave to the input and i want to see the output signal.what are the parameters i should consider...
  11. K

    [SOLVED] Need help in a Transistor Circuit ......

    As you can see.I built a circuit like above.I replaced 3.3Vdc instead of White LED(cant find them in my simulation software).The current for each LED suppose to get 11mA.but in practical board it is showing 4mA.Need to know what went wrong ?
  12. K

    [SOLVED] Circuit design help........................................

    this the circuit i built (transmitter and receiver)for my project,As you can see i kept 1 white LED.Instead of the voltage at R1,i kept frequency generator to give square wave. **broken link removed** the above picture is the waveform from the lm339 comparator when i used only 1 LED with the...
  13. K

    [SOLVED] Signal distribution using transistor .................

    my main object is ..i have 10LEDs i want equal current for all leds with the transistor 2N4401.i came up with this circuit design but not sure which one is a proper way. Led forward voltage = 1.4(approx in pspice), Led maximum current for each = 20ma Vce=0.4 Vbe=0.75 i am thinking the base...
  14. K

    [SOLVED] Transistor Connection correction

    is it the proper way to connect the two transistors ? i am not getting any waveform from the second transistor collector side.
  15. K

    How USB is different from RS-232

    How different are the USB and RS-232 ?? I know USB D+/D- works on a twisted pair and the speed is really different.I saw a lot of USB-RS232 converters(UM-232R)but i didnt find any converter in reverse.Why is that ,cant we convert the rs-232 data to USB ?
  16. K

    [SOLVED] Circuit solution for OPA355

    Circuit solution.............................. I got a problem given in my class ,trying to figure out the problem. 1. Design a two stage transimpedance amplifier using the picture solution: Since its transimpedance ( current to voltage conversion).So i have to design two transimpedance amps...
  17. K

    [SOLVED] How usb works internally ?

    I read a lot about USB functions but i cannot find proper explanation about how Data is exchanged.For example if i connect a device like my iphone(or any other USB devices) to my computer ,how the computer recognises and how the D+ /D- in usb pins work to transfer the data ? Thank you in...
  18. K

    [SOLVED] More bps interface terminal

    i am using terminal v1.9b ..but it has 256000bps as highest.is there any other similar one which has upto 921600bps ???
  19. K

    [SOLVED] need help with my project related to UM232R

    need help related to UM232R I used UM232R connected to my computer.I have connected Tx pin to Rx pin(terminal V1.9b is used for Bps control). it was not working fine. thank you.
  20. K

    [SOLVED] UM232R testing connection to computer

    I am testing UM232r (USB - Seriral UART) .. i have connected it to my computer (connected Pin 1(TX) to Pin 5(RX) for um232r) .When using the hyper-terminal , i am not able to get the characters i typed .. (used usb type a - type b cable to connect UM232r to computer usb port) - how to make it...

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