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  1. R

    Clamping circuit for PIC A/D

    Hi, I was wondering if someone could help me. I have a 60V pk to pk signal, which has a current of 200uA, so not much. I need to clamp this so I can feed this to an A/D input of the PIC microcontroller (PIC18F). The PIC can have its A/D from 0-5V My solution is to use a resistor and zener diode...
  2. R

    Electronics help

    So please could you explain why the 1/4 wavelength is so important? Thanks in advance
  3. R

    Electronics help

    Thanks Bob for the great explanation. I understand it now :)
  4. R

    Electronics help

    ok so your example was this: 300 / freq(in MHz) = wavelength ( in metres) eg 300 / 150 MHz = 2 metres rework the formula to give you frequency frequency will then be ; wavelength / 300 i.e. 2 metres / 300 = 0.0066 MHz Is that correct? So if I have a track length of 10cm, using a frequency of...
  5. R

    Electronics help

    What is meant by 1/4 wavelength in relation to pcb tracks and how they radiate. Can someone gives simple answer with some working outbid the equations involved. Also capacitor selection to minimise effects of radiation through pcb tracks. Thanks
  6. R

    Electronics help

    Thanks all for the help. I have another question. How can I calculate at what frequency a track length will radiate? For example if my track length was 4cm, what frequency will that radiate at? Thanks in advance
  7. R

    Electronics help

    Thankyiu all for your help and answers. Much appreciated. Could someone please give me an example (simple one to start with) on what track would radiate at what frequency? Thanks in advance.
  8. R

    Electronics help

    Hi, Please could someone explain the difference between solder paste, solder mask, solder resist and paste mask. It confuses me. My second question is what is the connection of pcb track length with wavelength? How can a track become an antenna at certain frequencies. I look forward to any help.
  9. R

    A/D source impedance

    Hi all, I am looking to do some A/D measurements with a PIC microcontroller. The PIC datasheet states that it has a source impedance of 10K. Does this mean, I need to drive it with something that is lower in value so that it won't load the signal. I have a voltage divider connected to this pin...
  10. R

    understanding discrete circuits

    Thanks for the help guys. Perhaps this was a bad example. I will post another circuit later that a friend of mine did. Thanks again.
  11. R

    understanding discrete circuits

    The question is I wouldn't know how to describe the circuit function. For example what is the purpose of C2 and R2, is it a low pass filter? Then why is this connected to C1? What happens when Q3 switches on? I put this circuit as an example to highlight my lack of understanding. So could...
  12. R

    understanding discrete circuits

    Hi all, Here is a typical example of a circuit that I can't understand and explain fully. I know it is to drive a loudspeaker, but why all the transistor interconnections is what that confuses me first. . Any help would be appreciated. Best regards, Raj
  13. R

    Wanted: Oscilloscope help

    I'm a bit confused. Do I need a DSO with logic analyser functionality. My PIC microcontroller work will revolve around a 4 MHz click, any analogue electronics will be around 50-100KHz. With that in mind please could you advise on following parameters for a scope, Bandwidth, sampling rate, would...
  14. R

    Wanted: Oscilloscope help

    Sorry, it was meant to say Rigol and Instek. Predictive text on the smartphone is pretty poor. I thought I can buy a DSO and then there is a firmware upgrade to allow for SPai, I2C etc
  15. R

    understanding discrete circuits

    Thank you all. I will post some circuits. Best regards, Raj
  16. R

    understanding discrete circuits

    Hi, yes I will show some circuits. I will post a couple later, the issue being I can't see what the interconnecting components and circuits in general is trying to do. Thanks for your reply My OND was done around 10 years ago.
  17. R

    understanding discrete circuits

    Hi all, I have a Btec OND in electronic engineering. Which I qualified for a few years ago. My question is that I find it difficult to analyze circuits that I have seen to figure out what is going on. Something with say 3-4 transistors NPN and PNP starts to baffle me. I look at a circuit and...
  18. R

    Wanted: Oscilloscope help

    Also should I go for a 2 or 4 channel type. Any help would be appreciated. Best regards, Raj
  19. R

    Wanted: Oscilloscope help

    Hi, I am looking to purchase a oscilloscope, my budget is not great. But I will be using it for the following experiments. 1. Monitoring SPI, RS232,I2C signals using PIC microcontroller 2. Analogue elevtronics, filter design and simple circuits like waveform generation 3. Basic digital...
  20. R

    Understanding impedance

    Wow, so much to learn. Thanks for the advice. Another question. I have always read that a circuit should have high input impedance and low output impedance. Why is this. Can someone explain. I thought a high impedance doesn't draw much current and low impedance can. Is this correct?
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