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  1. duke37

    decimals,division..ohms,kilohms...amps,milliamps.. I am so confused I need help!!!!!

    I have had an e-mail giving another post but it has not appeared here. Your equation for resonant frequency includes the number 3.3*10E-3. This should be written 3.3E-3 which is 3,3mH. the 3.3 is indeed multiplied by 10 to the power of -3 (divided by 1000) but adding the 10 only increses...
  2. duke37

    decimals,division..ohms,kilohms...amps,milliamps.. I am so confused I need help!!!!!

    Glad that I could be of help. Early IBM computers could not deal with anything other than simple upper case characters and used a system of numbers with E followed by the number of 0s to be multiplied. Thus 1000 became 1E3 and 1/1000 became 1E-3. This is the system I often use and my calculator...
  3. duke37

    Substitute transistors

    As you appreciate, there are thousands of different transistors in dozens of packages. You would be wise to get transistors as you want them, possibly buying a few extra to make up a stock of those you are more likely to use. If you want a list of common types, look at circuits on the internet...
  4. duke37

    decimals,division..ohms,kilohms...amps,milliamps.. I am so confused I need help!!!!!

    You know that the trouble is that you do not bother with multiples or submultiples. If you work in fundamental units - A, V, Ohms iin your calculations then things will turn out right. With more experience, you can work in multiples, shifting the decimal point usually three places. In the case...
  5. duke37

    active filter design

    I do not understand the question, however, It does say use the filters in cascode, I assume that this means in series. Your circuit has the two filters in parallel so that even if one filter rejects some signal, it will be supplied by the other filter. Try your 2 filters in series, adjusting the...
  6. duke37

    toshiba 50871 rptv rainbow at top and bottom..

    Perhaps the TV has been placed near a magnet, has it been moved or have speakers been placed nearby?
  7. duke37

    Please Help with a (supposedly) simple RL Circuit Problem

    lexrosas point 3 The impedance of a series RL circiut is not the arithmetic sum but Z=SQRT(R*R+X*X)
  8. duke37

    High Pass Filter Design?

    Hi Martin, I don't know the best op-amp, I am still working in the age of the 741. I expect there are better ones around now.
  9. duke37

    High Pass Filter Design?

    I have looked at a 3 pole Butterworth filter. I have used all capacitors at 100n and selected resistors to the nearest preferred value. Will try to attach the diagram. I have 'tried' it with 5SPICE.
  10. duke37

    High Pass Filter Design?

    Hi Martin, I'm no expert but I have a book "Electronic Filter Design" by Aurther B. Williams. This gives normalised values for various filters, the most tolerant would be the Butterworth filter and I could calculate the values for, say, a three pole 200Hz high pass active filter (no inductors)...
  11. duke37

    transformer amperage

    No. Transformers are designed for a particular purpose. If the voltage is transformed down by a factor of 2, then you would expect the permitted output current to be increased by a factor of about 2. With multiple secondaries, the permitted current in each secondary will depend on the wire...
  12. duke37

    What is impedance?

    Only with no reactive components or with direct current. The maths can be complex, see Wikipedia.
  13. duke37

    High Pass Filter Design?

    Noswaith dda The rolloff frequency will be R.C., say 500k and 100nF. The actual values will depend on the output impedace of the microphones and the input impedance of the amplifiers. The rolloff will be very gentle with just a RC filter and it may be better to make a pair of active high pass...
  14. duke37

    Eq. Parts for an AM radio project

    Crystal sets used no external power, relying solely on the energy derived from the aerial. Thus it was essential to use a detecting diode with very low voltage drop (germanium not silicon). In your case, you have a voltage supply which can help. If you turn the diode around and add a resistor...
  15. duke37

    question about temperature of amp output transistors

    The amount of heat generated will depend on the power supply voltage (which is not given)as well as the current drawn. Drilling holes in the cabinet will help only a little, it is far better to use heat sinks to spread the heat. You can use commercial heat sinks but I have used flattened copper...
  16. duke37

    transmitter antenna

    Anything which conducts can be coupled at any frequency, the efficiency may be very low however. For a simple aerial, it is usual to drive a half wave at the centre. At 14MHz, the aerial will be about 10m long and will show a drive resistance of about 50 ohms which modern amateur radio...
  17. duke37

    LM324 buffering doesn't work

    I have had another think, it takes time these days. You should check that the phototransistor is not saturated in ambient light, use a high impedance voltmeter to measure across the 1M resistor. The first op-amp can then be directly connected as you have it already. If the transistor is...
  18. duke37

    LM324 buffering doesn't work

    The diode direction looks OK to me. I would shift the 5k6 resistor to the output and add a capacitor to ground there. I suggest that the problem is too much DC giving permanent offset. Try a capacitor (10nF?) between the photo transistor and the first op-amp and add a 1M resistor to give DC...
  19. duke37

    help needed in analyzing this circuit

    It looks as if the circuit will not work without a DC path for the diode. Add a resistor from the junction of C and the diode to ground. It would also help if there was power to the amplifier!
  20. duke37

    Ultrasonic Distance Sensor/Alarm

    I have a vague recollection that some loud speakers were made with the driver facing upwards. Above the driver was a 45 degree cone pointing towards the driver. This was supposed to distribute the sound over 360 degrees. I never heard or saw one so don't know its effectiveness
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