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Type: Posts; User: c_mitra

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  1. Closed: Re: how to design a thermostat without Microcontroller?

    This should control the amount of hysteresis; in other words turn on and turn off points.

    The difference between the turn on and turn off points is called the hysteresis.

    It should turn on at...
  2. Closed: Re: how to design a thermostat without Microcontroller?

    You still need to work on the span control (the hysteresis range) and the temp setting.

    In the present case, they are strongly interacting. You should be able to set the actual temp and the...
  3. Closed: Re: how to design a thermostat without Microcontroller?

    My suggestions are as follows:

    1. Put a ceramic cap (0.1uF is sufficient) in parallel with C1.

    2. Replace C3 with 0.1uF ceramic cap; also put a resistor in parallel 1K will be fine).

    3. Put...
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    Closed: Re: Soldering on Battery Terminals

    I know but the paste will be still effective with graphite (graphite powders are easily available from science labs: that is where I got them!)

    Most of the epoxy must have about 30% (v/v) of...
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    Closed: Re: Soldering on Battery Terminals

    The battery terminals are also tough to solder; somehow the solder does not like to stick. It works for Zinc surface with some difficulty.

    Welding with thin Ni strips is not very tricky - I saw...
  6. Closed: Re: Does it exist an AC to AC converter in small package for converting 220v to 110v?

    I do not understand the graph you have attached: why the RMS and the power graphs are different? They should be identical.

    There are some hidden assumptions here.
  7. [SOLVED]Closed: Re: Iron sheet laminated gapped core inductor variation

    You are correct.

    For small excursions of H (i.e., the current in this case), far from the saturation limit, the B-H curve can be considered linear and hence the mu should be approximately...
  8. [SOLVED]Closed: Re: Iron sheet laminated gapped core inductor variation

    Please elaborate; this is not correct.

    If the quantity called permeability is a constant, then the B-H curve would be a perfect straight line. That it saturates means that the permeability is NOT...
  9. Closed: Re: how to design a thermostat without Microcontroller?

    I do not understand; what is the expected output of LM35 at 37.7? Remember that the device is basically a current source and the opamp is a voltage device. Hence a resistor is needed from pin 2 of...
  10. Closed: Re: how to design a thermostat without Microcontroller?

    I doubt. The relay is not a power hungry device and it will work happily upto 3-4 v coil voltage.

    I suspect noise as the main culprit. You are very miser with capacitors. The inputs of the op-amp...
  11. [SOLVED]Closed: Re: Iron sheet laminated gapped core inductor variation

    I am not so sure. The current is responsible for the magnetic field (H) and that is in turn responsible for the induction (B).

    In other words, when you try to calculate B directly, you are using...
  12. [SOLVED]Closed: Re: Iron sheet laminated gapped core inductor variation

    Ok, you should have used B, rather than H. But that is a minor point.



    Approximately correct.

    If I use the graph presented in #7, the H values (199/108 A/m), the mu values you use are...
  13. [SOLVED]Closed: Re: Iron sheet laminated gapped core inductor variation

    Puzzled; I checked some unit conversion tables and 1T=798 kA/m.

    You have to calculate the magnetic reluctance for the overall path (include the gap) and then use that to get B.

    Or, am I missing...
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    Closed: Re: Why is Corner Frequency always -3db

    Are you confused? Don't worry, you are not alone!
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    Closed: Re: Why is Corner Frequency always -3db

    Actually it is related to logs and exponents.

    It is typical to consider 1/2 value, e.g., half life, half-power or half of some signal that decays exponentially.

    For an exponentially decaying...
  16. [SOLVED]Closed: Re: Iron sheet laminated gapped core inductor variation

    I assume the applied voltage is sinusoidal.

    Most common machines assumes that the device under test is a pure L /C /R. What is the approx resistance of the coil?

    Just for a test: make a simple...
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    Closed: Re: obtaining thermal rise in diode

    You need to make a steady state approximation.

    What I mean is that all the heat produced at the junction must be dissipated via the terminal ends.

    About 5W of heat must be conducted away from...
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    Closed: Re: obtaining thermal rise in diode

    You are right, well almost.

    The resistance has two ends; one end will be 57.5C if the other end is 0; if the exposed end is at 20C, the junction will be 77C. That is how I see it.

    In addition,...
  19. Closed: Re: Car battery STARTER voltage help (not charger) using variety of methods (possibly

    I guess there are two possible reasons: low temp (cold, long night) and weak battery. Typical lead batteries drop their voltage when cool.

    Yes, modern starters take lots of current to start. But...
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    Closed: Re: Energy harvest circuit questions

    Assume an antenna stretched along the electric field of the signal. For simplicity, consider the length to be lambda/4. In that case, when the peak of the electric field (consider a sine wave) is at...
  21. Closed: Re: Impedance frequency curves for ferrite beads

    Of course these are models made with RLC elements. At every point the three graphs satisfy Z^2=R^2+X^2. Therefore the three graphs are not independent. Given any two you can compute the others...
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    Closed: Re: Rotary capacitor physics and design

    You want a variable capacitor? What is the minimum and maximum capacitance you are looking for?

    They are commercially available; what is the special feature you are looking for?

    The range is...
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    Closed: Re: Design of 45 degree slant polarizer

    You are still ambiguous. If the incident signal is 45 deg pol with respect to horizontal, and your antenna is vertical, you will not get anything.

    On the other hand, if the signal is 45 deg...
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    Closed: Re: Design of 45 degree slant polarizer

    I hope I understand the question.

    If the signal is vertically polarised and your antenna is also similarly oriented (the dipole is vertical), it will receive at max efficiency.

    The same antenna...
  25. Closed: Re: How to they calculated resolution of the photodiode

    Resolution will depend on the original signal strength.

    You need to look into the noise specifications. The user has to decide the acceptable signal to noise ratio. If you are passing the...
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