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  1. dorke

    More questions about transformers.

    The circuit you have drawn doesn't agree with the schematics. The schematics looks rather strange though. The transformer secondary voltage should be 2x6.3+12.3=24.9Vac, you can check that. Why do you need to add a captor anyways?
  2. dorke

    Need help with this academic problem

    What is "academic" about it?o_O A high-school grade question. Hint: In a series capacitor circuit ,the lower a capacitor the higher the voltage on it, in a linear fashion regarding the values of the capacitances . You are given the voltage on the 500uF ,so you can easily find the value of the...
  3. dorke

    How to choose and where to get proper electronic fuses

    1. PPTCs are not very fast, they are as fast as slow-blow fuses. 2. You can get them from TE ,little-fuse, and others. 3. If you use a banana biding post like this one you can eliminate the need for the terminal blocks. 4. Your build should be very well insulated and use proper thickness wires.
  4. dorke

    More questions about transformers.

    Note that the 12.3V is AC. Show on the pic where exactly do you connect the capacitor?
  5. dorke

    Using 2 Sevent Segment to display only 0-15 decimal

    How are you asked do that ,hardware only or by software ?
  6. dorke

    Signal drifting/EM signal/Faraday cage/metal box with connector

    They are called "EMI/RFI shielded boxes",mostly of aluminum. You can make one yourself for much less,use any tin box and add the connectors you need for signals. and feed-through caps for power.
  7. dorke

    general pull down/pull up microcontroller input/output questions

    Yes,it is basic Zener stuff. Please enter the zener link in #8 for understanding it better. In short,, till the "Zener voltage is reached" the zener isn't conducting and the current through it is the leakage current.. When the zener breakdown occurs the voltage across the zener will remain at...
  8. dorke

    Clean square waves using a 555 timer?

    I have build this little 555 bugger circuit with an unknown manufacture IC. Tested it with an analog TEK465B scope ,probe at 10X(a cheap Chinese one...) The scope isn't good enough for that measurement (BW=100Mhz ),but that's what I have. The 555 was decoupled with a 15uF tantalum. Couldn't...
  9. dorke

    Transistors needed,

    Googled,they claim to be the best search engine,mostly as advertised...;) "rca1c03 equivalent", the 2nd result was it. Had to check the parameters agreed.
  10. dorke

    LM338 power supply problem

    Check the voltage between pins 1 and 2 of the LM338 should be 1.25V in all positions of the pot. Check the voltage on the pot in all positions. What do you get at max cw position and max ccw position?
  11. dorke

    Transistors needed,

    NTE291 and NTE292
  12. dorke

    Microcontroller block diagram

    Yes, and show the input mux select bits and output drivers connected to the i/o block. Add a timer/counter . Omit the the pic number-it is a general solution not tight to a specific one μC/μP
  13. dorke

    general pull down/pull up microcontroller input/output questions

    With a Zener-Diode that replaces R2, the R1 value should be lower at about 1kohm. A 1N4749A (24V zener) or 1N4750A(27V zener) can be used. The current in non-protection(Vi<24V) is about 5μA ( zener leakage). In protection ,the current can be 24ma for vi=48V. Is the 25V limit for for a 24V...
  14. dorke

    Microcontroller block diagram

    Something like that. Notes: 1. Each "sensor input " may have it's own resolution (translated to number of bits) and speed of change. 2. The output of a ADC may be parallel or serial. 3. It may be possible to use just a single ADC and multiplex the sensor inputs to it 4. Input from the sensors...
  15. dorke

    Microcontroller block diagram

    The inner architecture of the μP isn't at all important. A sensor polling scheme is well tailored for this application. You should have outputs to all control points. Take into account that the sensors are basically analog. and that a poling scheme may use a pol-timer. Hope you can complete...
  16. dorke

    general pull down/pull up microcontroller input/output questions

    1. The on/off pin draws a maximum of 15 μA 2.The TIP is an overkill,you should use a much smaller Tr like the 2N3904 or better yet a small MOSFET 3.You can provide protection from high battery voltage with a zener diode(25V) instead of the resistor. 4. You can omit R2 and use a higher value for R1
  17. dorke

    One on-off switch for 2 circuits ?!

    There are so many ways to do this. Do you use the 12V only for the LED? Are the LED and Lamp far apart or in different boxes?
  18. dorke

    2W Voltage amplifier help

    PAM =Pulse Amplitude Modulation
  19. dorke

    2W Voltage amplifier help

    Can you please post the datasheet of the AOM with the analog input. Is it's modulation PAM?
  20. dorke

    Clean square waves using a 555 timer?

    Not very complicated. Here it is,I have pulled out the output stage(totem-poll and drivers). We are left with a single input and single output to simulate,feed the input with a square wave at 10KHz or so. Just use a small signal NPN tr. model like the 2N2222 or 2N3904 etc. For the diode use a...
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