Search results

Search Forums New Posts
  1. duke37

    Regenerative braking dc motor controller

    Do you mean that the battery has 0V? The mosfet is connected 'upside down' and will pass current through its internal diode. D1 is connected so that it will not pass current. I would not know how to implement regenerative braking. As the motor slows down, the voltage it produces will drop...
  2. duke37

    Wind turbine project, wiring, etc.

    You must use enameled wire or the current will go direct from input to output, not round the turns. Wish you luck.
  3. duke37

    The 27 MHz Tx

    The feeback for oscillation comes from the capacitance in the transistor, transistor type may therefore be critical. The crystal does not ground the base, it will have a parallel and series resonance and the circuit will operate somewhere between these. If I remember correctly, the...
  4. duke37

    Oh what to do with a Tetrode tube????

    This looks to me to be an early tube, it will not have a separate cathode but will be directly heated. The filament will be a tungsten/thorium wire and will shine very bright. Voltages for the filament could be 5V, 6.3V 7.5V or 10V. You will need many amps. The high tension voltage will need...
  5. duke37

    Old Grundig Valve Radio Sound Problem

    Motor boating is almost certainly due to bad capacitors. I would go for the HT bypass smoother capacitors. You could get a 10uF or so capacitor and temporarily connect this across the bypass capacitors to find the faulty one(s). Don't kill yourself!
  6. duke37

    electronic push rod for hydrolic press

    Presses such as this are often designed so that two hands are necessary to operate the controls. This stops one hand being chopped off. Pressing a button and then letting the machine get on with it could be dangerous. There are hydraulic valve chests which trip when the pressure reaches a...
  7. duke37

    Direction of AC motor

    The motor will be series connected NOT parallel connected. This type of motor is called a 'universal' motor since it will run on AC or DC. This is how electric drills and hair dryers are made.
  8. duke37

    Oh what to do with a Tetrode tube????

    It has a grid so it is probably a triode. It is a power valve, perhaps similar to a 572B but for audio use (no top cap). It will need 1000V HT or more. Check which is the filament connections and on the shorted tube, whether the grid is shorted to the filament.
  9. duke37

    Can a step-down transformer be used as a step-up transformer?

    A mains transformer will not be greatly over designed and so 12V on its output will be taking the core close to saturation. Putting a larger voltage in will give core saturation and current will be limited by the wire resistance - Bang. More voltage can be used if the frequency is raised but...
  10. duke37

    Obtaining 250V, 500mA

    A voltage multiplier would not necessarily produce too high a voltage, it depends on the number of stages. It is unlikely to be small and will have difficulty producing a high current. Inverters have been used for many years to produce anode voltages for valves from a 12V source. You can...
  11. duke37

    ignition circuit for an internal combustion engine

    I presume that you have a battery, starter solenoid and motor and alternator to recharge the battery. The solenoid could be actuated from your switch if the battery voltage is 12V or under. When the engine starts, the battery voltage will rise to about 14V and this could inhibit the start.
  12. duke37

    Direction of AC motor

    Fans are made to various designs. Forward inclined vanes give high volume but low pressure. Backward inclined vanes give low volume but high pressure. B&D will have set the vane angle to the optimum.
  13. duke37

    creating a two stage alarm siren

    You do not say what you want! Ground connections seem to be getting closer to ground, that is good.. IC3 has no power. IC2 and IC3 are fighting for the output, this is not good.
  14. duke37

    Can a step-down transformer be used as a step-up transformer?

    Do you need DC or AC? You will need negligible current to test for insulation breakdown so you could use a voltage multiplier, this is two stacks of capacitors with diodes connected between them. You could make a high frequency inverter with insulation between each layer in the...
  15. duke37

    What does the 33uH coil in this circuit?

    Yes. I normally measure voltages relative to ground. You may want to measure voltages across components in other circumstances.
  16. duke37

    USB DSO Scope Probe ?

    500VAC is 707V peak, well above the limit on the X10 probe. Using the X10 probe with 50V input, the scope will show 5V.
  17. duke37

    What does the 33uH coil in this circuit?

    You are correct on average, however Q1 is an oscillator with the emitter fed by the 33pF capacitor. The emitter voltage will rise and fall, switching the transistor on and off. The 33uH inductor is there to allow this high frequency voltage to occur without loss. The base voltage is held...
  18. duke37

    Op-Amp premature clipping

    Your op-amp has two methods of setting its operating point and these can clash if things are not absolutely identical. Delete R1 and R2 and let the feedback work.
  19. duke37

    Hi

    Welcome from a Shropshire lad! Loveliest of trees, the cherry now / Is hung with bloom along the bough, / And stands about the woodland ride / Wearing white for Eastertide.
  20. duke37

    Relay "Ratings"

    10kV a bit much for a small relay, the gap may not be adequate. It is not the switching on that is the problem, here you have cold contacts coming together and the arc will only start when the contacts are very close and closing quickly. Switching off is a different matter, the arc starts as...
Top