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  1. duke37

    Power Supply current limiting ???

    Just install a 110V light and keep the systems separate. No chance then of blowing up the control box.
  2. duke37

    DC-DC Converter Design

    Normally, the transformer is connected in the drain leads of the fets. As you have it, the diode will short out the power when the opposite fet turns on. Also, to turn on the fet you will need a voltage way above the source, where will you get this from and how will you ensure that the fet is...
  3. duke37

    Please help with ultrasonic animal repeller circuit

    You could connect two leds in inverse parallel and then connect these through a 1K resistance to your sounder. If the circuit is operating properly, both leds will light.
  4. duke37

    Need Proper Schottky Diode of 100 Watt & operating frequency of 10KHz to 50KHz

    In what I think is your circuit, the fet and diode will have to deal with both high current and high voltage. The devices which will be optimum for high voltage will be less than optimum for high current. Thus high voltage fets will have a higher on resistance than low voltage fets. A...
  5. duke37

    Need Proper Schottky Diode of 100 Watt & operating frequency of 10KHz to 50KHz

    You are trying to do a difficult job. The devices will have to pass 10A and resist 100V. A better circuit would be the traditional push/pull transformer. Then the two fets would need to pass 10A but resist about 30V (IRF540) and the output diodes would need to pass 1A and resist >100V (UF4007).
  6. duke37

    Please help with ultrasonic animal repeller circuit

    An interesting mix of integrated cicuits. 1. I do not know what the switch does, if it selects one of the outputs of the Johnson counter, then what are the diodes for? 2. Most of the circuit is digital with either a high or low voltage at some point and a tip is that if you measure this...
  7. duke37

    Need Proper Schottky Diode of 100 Watt & operating frequency of 10KHz to 50KHz

    You will need to give more information. 100W could be 100V at 1A or 1V at 100A. Some details of the application would allow someone to help.
  8. duke37

    Relay for switching from one power source to another

    If you are using the same power supply (mains) for both speeds, all you need is a single pole changeover switch as used in two way lighting. The neutral would be common to both speeds.
  9. duke37

    I want to test this transformer

    It appears that your digital meter works correctly on a transformer with a large inductance, it is better than mine. In the UK we can get earth leakage circuit breakers which plug in and are used as safety devices for exra protection when using power tools. There must be connections in...
  10. duke37

    I want to test this transformer

    This might be difficult, my digital multimeter goes bananas when measuring the resistance of inductances such as this so you would be better off using an analog meter. Measure the resistance between all wires and draw a diagram of which wires are connected together. Some windings will have...
  11. duke37

    Foxhole Radio tuning help. My first circuit!

    Excellent job. Please let us know how you get on, have you tried a Shottky diode, have you fitted a capacitor across the speaker? What differences did these make? Will you be trying home made diode detector? Duke
  12. duke37

    ** Need Help Designing Automated 12v DC Motor Test Fixture

    A circuit such as this could work. I doubt if a wall wart could be found that is powerful enough but a battery charger and capacitor or small battery would provide a supply. Alternatively, CB power supplies at about 5A are available and have a controlled voltage. The circuit as shown just...
  13. duke37

    Traffic Signal Project

    The sequencer I made was based on a 4093 oscillator and 4017 ring counter. The 4017 has 10 outputs which are selected with diodes to drive the three fets. Diagram attached.
  14. duke37

    Traffic Signal Project

    I built a traffic light sequencer some months ago, running on 12V and driving 12V bulbs. The sequence was the UK sequence. This could be modified to switch 120V with relays or triacs but I, like Raven Luni, am not going to get into the safety problem. I will look up my posts to find the...
  15. duke37

    Sony tfm 1600W

    I could not get at the power supply part of the circuit diagram. Normally, the change over switch from AC to DC is built into the socket into which the power leads fits. Start by measuring the resistance between the power connections at the plug with the lead plugged in. If no...
  16. duke37

    12v regulator rectifier for motorbike PMA

    You cannot charge a 12V battery with 12V, you need 13.8 to 14.4. A LM317T 1A regulator can be set to such a voltage. It will need a power transistor across it to enable high currents to be passed. It will also need a heat sink to dissipate the exess power. An LM337T is the negative...
  17. duke37

    Foxhole Radio tuning help. My first circuit!

    A germanium diode is good but difficult to find on this side of the planet. The speaker is not a capacitace, it is an inductance. There will be some capacitance from wiring etc. but a small capacitor across the speaker enables the circuit to supply pulses of current through the diode without...
  18. duke37

    Foxhole Radio tuning help. My first circuit!

    The diode that you have is a power diode with a large internal capacitance and is slow. You would be better off with a 1N914 or 1N4148 which are very common. Even better is a small Schottky diode such as BAT43. A small capacitor (1000pF) across the speaker would also help. Crystal sets...
  19. duke37

    Bilateral switch for PWM

    Thanks Harald, I will have to learn how to draw a diagram easily one day. Since PWM is being used, there will be some voltage across the fet when it is turned off at all levels of demand. This can be rectified and fed to a capacitor to provide a power supply to drive the fet. A resistor and...
  20. duke37

    Bilateral switch for PWM

    You cannot use a fet in both directions but you could use a n channel and p channel for each direction. My suggestion was to rectify the current so that the polarity at the fet was the same whichever way the motor was running. The fet would go between the + and - terminals and the motor wire...
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