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  1. R

    Understanding impedance

    So if I have a voltage divider with say 2 x20K resistors, the output taken from the bottom resistor. Then the input impedance of the other circuit must be greater than 10 X the 20K resistor do the output voltage is not dropped or loaded. This is my basic understanding. But I still don't...
  2. R

    Understanding impedance

    Hi, I am a relative novice in Electronics. I can never truly understand the meaning of impedance. I understand it is a measure of resistance at AC (which includes inductance and capacitor reactance. What I can't understand is when I here for example 'This circuit has an input impedance of 10K'...
  3. R

    Wanted: Transistor Circuit Techniques Book

    Thanks I will have a look.
  4. R

    Wanted: Transistor Circuit Techniques Book

    I have got that one too
  5. R

    Wanted: Transistor Circuit Techniques Book

    Thanks for the message. I wanted to get better especially with transistor/analogue design. Is the book any good? The Kindle version is still pricey.
  6. R

    Wanted: Transistor Circuit Techniques Book

    Yes Gordon Ritchie
  7. R

    Wanted: Transistor Circuit Techniques Book

    Hi all, I am writing to see if anyone has the following book Transistor Circuit techniques by Gmail Ritchie. It's £48 on Amazon, I was wondering if anyone has this book for sale at a cheaper price :) Thanks in advance
  8. R

    sleep mode for PIC

    The program flashes an led on for 1 sec then off for 1 second. The port line driving the led is then made high. Note the led is driven by a pull up to 3v, cathode to pic I,/o line. The other ports have nothing connected, so I made them all o,/p and driven them low. The pic uses the internal...
  9. R

    sleep mode for PIC

    Hi, Thanks all for your replies. If I make the I/O ports as outputs and drive them low, turn off A/D, UART etc Would that be enough? Raj
  10. R

    Resistor across LED

    Thanks for the explanation. I think it may be to keep the LED off due to any leakage current. Brilliantly explained. I learnt something too. Thanks
  11. R

    Resistor across LED

    It might be, as this seems plausible. Then the port may be configured as an output, where it is driven to a logic 0, then only the LED and 680R come into play. Not sure. That's all I can think.
  12. R

    Resistor across LED

    Yes me too. I can only think of the suggestion made earlier. Input with 10K + 680R, then output set to logic 0, so LED and 680R are in circuit.
  13. R

    Resistor across LED

    Hi, It's a I/O line of a PIC. To turn the LED on the I/O line would need to be set low. That's as much as I know. Unless it is set as an input in that case you will have a 10K + 680R pull up, then reconfigured as an output to switch on the LED. Does that seem reasonable? Best regards, Raj
  14. R

    Resistor across LED

    Hi all, I have a question. There is a circuit of an LED and 680R resistor. The LED is powered from 3V, the 680R is driven from the I/O line of a PIC, so a logic 0 will light the LED. However, across the LED anode and cathode is a 10K resistor. What is the use or idea for this? Can anyone help...
  15. R

    sleep mode for PIC

    It is how to set the configuration bits and I/O bits to reduce the current consumption further.
  16. R

    sleep mode for PIC

    Hi I am using a PIC 18F4550 and want to put it into sleep mode to conserve battery life then wake it up using a 'wake up from interrupt' My question is what I need to do with the I/O lines? A basic sleep function will put the PIC into a mode which it consumes around 40uA. However, if other...
  17. R

    Thick or Thin Film Resistors

    Hi, I wanted to ask if I have a thick film resistor with the following specifications: Case size 0603 Tolerance +/-1% Voltage 50V Value 10K Temp coefficient 100PPM/C Application is for ultrasonic level measurement Can I replace this with a thin film resistor with a like to like spec? Or are...
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    General question regarding fuses

    Dear all, I have the following circuit 'A' -----------------| Fuse 315mA |----------------- Battery Positive + (3V) ---------------------------------------------------------------- Battery Negative - (0V) The battery is 3V. If I short out from point 'A' (fuse side) to...
  19. R

    2 x 16 lcd 4 bit mode

    hi all, I am using a pic to connect to a 2 x 16 lcd in 4 bit mode. I can get the cursor to blink on and off, also move to any position on line 1 or 2. however when I come to display character the screen goes blank. I am using a pic18f4550 and pic dem plus (microchip demo board). here is my...
  20. R

    Reaction Game

    Hi, I just wanted to know this is my idea: for example 2 LEDs are lit (these will be on PORTB 0, 1, 2, 3 of the micro. Say bit 1 and Bit 3 are lit. I need to mask these off and then compare the appropriate switches connected to PORT B bits 4-7, so the key presses will be bit 4 and bit 6. I...
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