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  1. duke37

    Self-made transistor RAM

    Chips are very reliable, it is the connections between them which are the problem. 100 bytes = 800 bits I think you will need two transistors for each bit = 1600 transistors plus maybe the same number of resistors. Relays are not very reliable as was found when decrypting the Enigma...
  2. duke37

    I don't "get" capacitor usage if it blocks current

    Think of a capacitor as a rubber diaphragm in a water pipe. If the pressure goes up and down, the diaphragm will flex and pressure will go up and down on the other side. (AC) If the pressure rises on the input and stays there, the diaphragm will flex and water will come out the other side but...
  3. duke37

    Recordings=actions

    Microphone Audio amplifier Level detector Time delay Switch (transistor, fet, SCR or relay)
  4. duke37

    Samsung 2223NW overheating

    It Is midsummer and I am shivering ! What is the age of this device? If it has been in use for a few years it may be very dusty which will reduce the cooling. Try giving it a good blow out.
  5. duke37

    Comparator IC

    What do you need to do? Find the highest, find the lowest, see if two are similar?
  6. duke37

    Help with Small Project Please

    A 120V AC motor may not like being fed with a low voltage. I would go for a 12V DC fan out of a car heater. This will have plenty of waft and will be easier to control with low voltage, safer electronics. A 12V fan out of an old computer power supply may be big enough. The DC fans can be tested...
  7. duke37

    Capacitor Value issues (simple)

    12000pF or 12nF?
  8. duke37

    Is RF transmitting electrons over the air?

    Leds emit photons, the eye is most sensitive to green which is about 500nm wavelength. Radio waves are no different other than the wavelength (frequency). The energy is transmitted as a electrostatic and magnetic wave. I cannot help with the physics but there will be no electron movement...
  9. duke37

    Microwave Transformer Isolation

    I may be wrong about the autotransformer, it has been known. The live core means that if the core is insulated and allowed to rise well above the input winding, then the insulation may be compromised. I put the microwave to one side as I did not have the courage to repair it.
  10. duke37

    Old Component Equivalents

    These are the components for a single band superhet radio using germanium transistors (positive earth). The transformers colours do not mean anything without knowledge of the maker. You are not likely to find all the components at least at reasonable prices. You could however find an old...
  11. duke37

    need help with a speed variator

    If you chose 5A as the current with 24V then the power will be 120W. I assume you wish to measure the speed of the motor. There are many ways of doing this, you can get revolution counters which can be pushed on the end of the motor shaft. Hold it there for a minute say. You can put a...
  12. duke37

    Microwave Transformer Isolation

    The microwave transformer that I have seen is an auto transformer with no isolation. If the core is connected to either input or output, then insulation may not be adequate to connect it differently.
  13. duke37

    Stamford C20B Alternator Looking to identify VCU Components

    I do not know what the diode is but would suggest that you use a 15A 600V diode to match the SCR. Without the circuit it is difficult to give more advice The VCU is encapsulated so can only be tried in situ.
  14. duke37

    need help with a speed variator

    C2 is to smooth the power supply to the 555 so that false triggering is reduced. The TIP33 is rated at 10A. R5 will determine the base current of the TIP33 which will be the limitation. You could take output current to be at least ten times the base current.
  15. duke37

    Electronics newbie needs help with power assist scooter

    Some comments. A dynamo can be used as a motor so you will not need a separate motor. The amount of energy reclaimed will be low. You will need a complex circuit to adjust the dynamo voltage to the battery voltage. You will need a complex circuit to adjust the battery voltage to the...
  16. duke37

    rain warning device

    Kris I do not know whether it is plain copper, it is quite brown and there is a white stripe on it, I thought it was pigeon poo but it would not come off with a plastic scrubber so it is probably paint. I did not want to rub the tracks down to bright metal. shunbrook I made an...
  17. duke37

    rain warning device

    A new terminal block purchased from R.F. Potts, Derby for £0.20 Fitted and posted today. The board has interdigital tracks and needs a quarter of it to be wetted to work. The resistance is then about 100k. The circuit uses a 7555CN (CMOS 555), 2 transistors and a sounder. Battery is 9V...
  18. duke37

    Voltage Suppression

    The voltage transient will be due to the fact that the current in the inductor (relay) cannot be instantaneously be stopped. A free wheel diode across the inductor is normally used to carry this current until it dies from circuit resistance. A transistor does not like its rated voltage being...
  19. duke37

    Help needed for fixing circuit board

    Hi Daniel I think you will get into trouble with the moderators if you jump into someone elses thread. I would doubt if the board is running at high voltage, if not, then there will be no line or neutral. The board contains diodes so possibly runs on AC. Does the supply come from the...
  20. duke37

    power supply for a printed resistive flexible heater

    The resistance of a square of conductor is independant of size. The required power will be proportional to area.
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