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  1. duke37

    Noise with the Phototransistor output

    I counted 50 spikes in one second so it looks as if you are not in north america. The noise should be reduced by careful earthing and screening. Rectifiers should have small capacitors across them to soak up the interference. Tests with a battery could determine whether the interference is...
  2. duke37

    LM741 Integrator and Audio Amplifier circuits

    A 741 is usually chosen because it has been around since the beginning of time and everyone knows it. Op amps are not ideal so other op amps may be more suitable for:- Power voltage range. Inputs down to negative line Very low input current High frequency operation. Multiple amps on one...
  3. duke37

    Need help fixing/understanding rotary grill

    You have not said if there is a short with the power switch off. Progressivley disconnect the switch and see where the short disappears. The timer may have a short. The motor seems to be mains driven and will not be damaged by anything you do.
  4. duke37

    What Is The Ohm Of This Resistor

    I have looked at several fencers, mostly Gallagher, but not come across a Fieldmaster. There are many wires connected to the board Red, black, green 2 black 2 blue? 2 yellow yellow, green What do the wires connect to? What is the power supply? What is the IC ??324KN ? Are the...
  5. duke37

    What gauge do I need?

    There will not be any problem with cable heating, the problem will be with voltage drop on starting as Chris says..This can be calculated using the wire resistance. Compressors can be difficult to start since they may be pumping the air during start and they often have a heavy flywheel.
  6. duke37

    What Is The Ohm Of This Resistor

    It could be in the 100k range. Hard to see how a high resistance could be burnt unless it has been hit by lightning. What is the make and model of the fencer?
  7. duke37

    Current measuring problems

    If you take two resistors of 100k in series from one sde the sense resistor to ground and another two at the other side of the sense resistor to ground, then connect the op-amp to the centre of the resistor chains. This in effect will replace R1 and R3 The op-amp input resistance will be 50...
  8. duke37

    Current measuring problems

    Some comments. The LM357 can measure down to ground but a look at the IC circuit would indicate that it cannot measure within a couple of volts or so of the supply. Dividing the input signal by two could be used. The LM317 needs input and output capacitors to stop oscillation. The B2...
  9. duke37

    Automated Sliding Door

    I am sure it can be done with relays and a timer. It would be simpler to use a timer with two outputs if they exist, to activate open and close. If you go the Arduino route I cannot help. It is 30 or 40 years since I programmed a microprocessor.
  10. duke37

    Automated Sliding Door

    I think this can be done with three relays. One to turn on forward and latch, limit to turn off One to turn on reverse and latch, limit to turn off One to change over the motor polarity, connected to either forward or reverse relay coil to define direction.
  11. duke37

    Sending power and control over single coax

    You said that you knew how to combine two signals on to the co-ax cable so I did not bother to draw that. I suggested using 12VAC which is rectified to take the positive half cycle. This is rectified again to provide a DC supply for the LM3914 and up to ten relays. The negative half cycle...
  12. duke37

    Sending power and control over single coax

    I have had a cogitate and think the attached circuit may work. You will need a few extra resistors on the LM3914 to set the range. NOTE that the second diode from the transformer is the wrong way round
  13. duke37

    firing circuit

    TYN612 600V 12A gate 30mA 1.3V
  14. duke37

    Sending power and control over single coax

    I was looking for a similar circuit and thought that a telephone dial running a uniselector would do the job but I never found a circuit, perhaps someone here knows. Different DC voltages on the line could switch different outputs. You could use pulses with the peak level to run the circuit...
  15. duke37

    DC to AC 50/60Hz Same Voltage IN/OUT

    Even if you can find a relay which will work at 50Hz, it will not last long. An H bridge using fets can do the polarity change over. A push-pull circuit driving a transformer (heavy) can be made with two fets. The CMOS 4047 has an oscillator and will drive the two fets but there are other...
  16. duke37

    firing circuit

    Different thyristors will need different drive levels There are thyristors with sensitive gates such as the C106 and others which need more drive. For electric fencers needing one pulse per second, I have used :- 1. Neon indicator bulb. 2. Diac 3. CMOS gate For phase angle control you will...
  17. duke37

    design a water level alarm system

    If you have 0 to 1V input, how do you have input up to 10V. The LM3914 I.C. can provide switched outputs at various input voltages. A thermostat is used for switching at a certain temperature. I do not know of one which will work in water. Consider using a thermistor. A 555 can generate a...
  18. duke37

    (woo woo) transformers 1:5 ratio - were to buy

    For a ratio of 1:5, you can use a 5:1 transformer in reverse. So 220V to 44V will be 5:1. I do not think the ratio is critical. If this method of generating power is so good, do you run your computer on it?
  19. duke37

    Data logging from a Ugandan toilet - please help

    Perhaps the resistivity of the liquid could give an indication of urine content. Electrodes in the liquid would get contaminated but it may be possible to measure using inductance.
  20. duke37

    How does frequency affect voltage

    Your cell does use a solution. Pure water is an excellent insulator, it is the impurities in the water which allows current to pass. High power valves (tubes) are sometimes cooled by water with thousands of volts across the pipes. The water has to be very pure.
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