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  1. R

    Measuring CR123A battery using PIC A/D

    Hi Bob, Thanks for your help. The PIC does have an internal VREF. I am slightly puzzled, if I use the battery as a reference for off-load calculations. Are you saying that I need to then re-configure to use the internal VREF (after the off-load test). Then use the A/D value for the off-load...
  2. R

    Wanted: Everyday practical electronics teach in 2002

    I can pay you for the PDF versions if you prefer.
  3. R

    Measuring CR123A battery using PIC A/D

    Hi Bob Yes i thought off load i will get the same value, which is what i want. But on load it will be different as i have a potential divider circuit. This will give me a delta. Which as long as it is in a certain range, i know the battery is good. Does that seem correct? Or is there a better...
  4. R

    Wanted: Everyday practical electronics teach in 2002

    Would it be possible for you to send the link please? For the online version. Thanks
  5. R

    Wanted: Everyday practical electronics teach in 2002

    Hi I am trying to get copies or pdf copies of the entire EPE Teach In 2002 series. I have tried theire website but cant seem to find these. Does anyone here have copies or know where i can find them from. Thanks
  6. R

    Measuring CR123A battery using PIC A/D

    Hi all I have a CR123A 3 V battery. I am trying to monitor the condition of this using a PIC 18F45k20 A/D. This is my approach. 1. Use the Vdd and Vss of the battery as my PIC reference. This will be used to measure off load battery levels. 2. I then intend to use a voltage divider 30K top...
  7. R

    Pcb as antenna track

    Hi Thanks for the help much appreciated. Am i wrong in thinking the track should be 15.18cm in length (as per your calculations)? I have a few more questions 1. How would i work out the width of the track 2. If i wanted to match it to say a 50 ohm impedance. What would i need to do? Is it a...
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    Pcb as antenna track

    Hi thanks for the reply. I worked it out like 3x10 (power 8)/433MHz=0.70cm Then dont i need to divide be 4 to get 1/4 wavelength? Is there anywhere or some info available to explain when this track is placed on the PCB. Some simple examples?
  9. R

    N channel Fet v npn

    Hi If i drive it greater than vgs does that mean more drain current?
  10. R

    Pcb as antenna track

    Hi all I am looking at doing a project with 433MHz radio modules. I think that 3x10 (power8)/433MHz is 0ne wavelength. If i divide this again by a quarter to get a 1/4 wavelength. Just say this came to 7cm as an example. I want to know how i can make a PCB track to act as an antenna. Say it...
  11. R

    N channel Fet v npn

    Yes i meant a n channel FET. I just want to know if i have a logic Mosfet n channel controlled from a PIC I/O line. What do i need to consider for the gate drive? How do i control ID drain current to light the LED? I was thinking off puttibg a resistor to the gate pulled to 0V. So it doesnt...
  12. R

    N channel Fet v npn

    Hi all I was after some help regarding n channel fets v bipolar npn. I want to conduct a simple experiment so I can understand the differences when using these transistors as switches. I want to switch an led powered from 9V using both transistors. So basically 2 different circuits. One with an...
  13. R

    Pressure sensor for focus pads

    Hi all, I am starting a project that will display the force that someone has hit a focus pad. This will be used for boxing practice. The idea being yiu hit a focus pad and then a displsy registers how hard you have hit the pad. I am a little stuck on the method to detect the strike. I was...
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    switching the VSS line of an IC

    Dear all, I have a IC which I need to switch off when not in use as it draws a current of 100uA in standby. I think the best way of doing this would be to disconnect the 0V line via a switch i.e. transistor or FET. I have one pin of my PIC I/O line which I could do this with. I am looking at a...
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    EMC good practices

    Hi I was wondering if someone could help me with the following EMC and PCB layout questions: 1. Why is it good to have a separate layer dedicated to the GND? Is it because it is a low inductance/resistance path to ground? i.e. less voltage spikes? 2. Are track lines meant to be short as...
  16. R

    Detecting an active low signal

    Hi The connections available on the main PCB are as follows pin 1 VCC pin 2 MISO pin 3 MOSI pin 4 CLK pin 5 SS pin 6 - pin 7 - pin 8 GND I thought I was in luck with pins 6 and 7 as they do not connect to any other pin. However on the Top PCB that plug into this PCB pins 6 and 7 are as follows...
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    Detecting an active low signal

    Thanks for the reply. I will post a pinout of the connections. Its a 2x4 connector (2.54mm pitch) PCB mounted through-hole from SAMTEC. This sits on the main PCB. The other smaller PCB has the mating end thst plugs into this. I will get the signal pin outs for you. Thanks again.
  18. R

    Detecting an active low signal

    Yes i get what you mean. However i only have one pin on the connector that is free. What would be the best way to tackle this? If for example there were no free pins could i use the SPI pins? I am not sure on this. Thanks for the help so far much appreciated.
  19. R

    Detecting an active low signal

    Hi thanks for your reply. I am not 100% sure what you mean. I have a Vcc and Gnd on my connector aswell as the SPI pins. Are you saying connect the VCC pin via a pull up and then feed to the PIC input I/O pin? That i understand. I am not sure what you mean by the other pin ? Are you saying...
  20. R

    Detecting an active low signal

    Hi all I need some help with a problem. I have 2 x PIC microcontrollers on seperate PCBs that communicate via SPI. They connect via a 8 pin header. One is a master the other the slave. I need to detect when tbe slave PIC has bern disconnected from the header. I have MOSi, MISO,CLK and Slave...
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