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  1. duke37

    Why am I not getting 37V on a 37V line?

    24.5*sqr(2)=34.6 so you would expect about 33.5 out, unloaded. The figures are not consistent. To get closer than this you need to consider actual mains voltage.
  2. duke37

    A light-sensitive motor

    The resistance of the motor does not mean much. A 100% efficient motor would have zero resistance. The current taken by the motor will be dependant on the applied voltage and the speed. A spinning motor produces a back emf and the current will be the difference between the back emf and the...
  3. duke37

    Chronograph for bullets

    Bob A bullet is intended to transfer its kinetic energy into the target so I would think it is large Duke
  4. duke37

    Timing coil transistor output to transistor?

    I do not understand what the circuit with 120V has to do with a motorcycle ignition circuit. The transistor will be turning on when the base voltage is rising above 0.7V. The transistor will be damaged when the voltage is negative, 5V reverse voltage is enough to keep the transistor off. To...
  5. duke37

    Chronograph for bullets

    "This works on the principle of conservation of energy, that all kinetic energy of the bullet goes into potential energy in raising bullet and block. " But energy will be lost as the bullet enters the block. Surely it should be done by conservation of momentum.
  6. duke37

    Help needed!

    Nos da Op-amp The batteries should be connected to give a positive supply and a negative supply to the chip. The output voltage will be the invert of the input voltage and could go close to the two power lines. The input signal would normally be somewhere near the 0V rail Transistor...
  7. duke37

    Frequency locked loops

    The 4046 data has two comparators. It would be difficult to make one of these in discrete components. Can you make an exclusive or gate? If the frequencies are locked, then the phase difference will be constant so I do not see the difference between frequency lock and phase lock. FM radios...
  8. duke37

    DC transformer power supply question, 9V dc too much ?

    12W in, 3W out. Almost certainly a lossy linear supply.
  9. duke37

    question about question about motors, speed controllers and power supply

    The torque will be from zero to 16Ncm (not 16ncm). It is better to use the SI fundamental units i.e.Nm. Fundamental unit of rotational speed is radians per second. 1920rpm = 1920*2*pi/60 = 201rad/sec Power = speed * torque = 201 *0.16 = 32W Power = Voltage * Current so Current =...
  10. duke37

    question about question about motors, speed controllers and power supply

    The data I saw said 3000 rpm not 6000. The voltage on a DC motor is approximately proportional to speed so the voltage at 1920 rpm will be 14.5 * 1920 / 3000 plus a bit for drop across the brushes. To adjust the speed of the motor, you need to adjust the input voltage. The current taken...
  11. duke37

    Voltage Amplifier with an OpAmp & two NMOS help! :)

    I am not into detailed mathematics of circuits but it seems to me that an aproximation can be made. The op-amp will have its inputs at the same voltage so the two drain currents are the same and equal to half the tail current. The negative feedback will adjust the voltage on the two gates to...
  12. duke37

    Call it feed back.

    Welcome back Dave, I hope it was not me who upset you. I read the posts to get information and learn more about electronics. Occasionally I can see obvious errors and put in a comment. Sometimes I can see a simple solution and I post it. Many times the person asking a question has not...
  13. duke37

    Cold Smoker blower

    You can get a small 12V fan out of a computer power supply. A multiway switch to switch in series resistors will vary the speed. Start experimenting with 10 ohm. More powerful 12V fans are used in car heaters. These probably take more current than a simple all wart can supply.
  14. duke37

    Looking For A Low RPM <30rpm Motor

    Do the works out of a microwave cooker do what you want? It has a slow motor and a bearing to take the weight. If you take one out of a dead microwave be very careful of the very high voltages which could still be present inside.
  15. duke37

    Amplifer help!

    The upper and lower resistors in the detector are presumably similar so the output will sit about half the supply voltage. This is compared to the adjustable circuit. You have divided down the detector output with R6 and R7 so things are unlikely to match. Why not take the detector output...
  16. duke37

    Amplifer help!

    This part of the circuit just supplies a voltage as a proportion on the input voltage. If you have a bridge, you should be measuring the voltage across the bridge. What else? Show us the bridge.
  17. duke37

    Motor Resistance as Generator

    If it is a motor with carbon brushes,the brush/commutator resistance is not constant and is higher when stationary. This effect will depend on brush composition which is sometimes loaded with metals. The heating in the motor will depend on the current and the speed (which will cool it). Do...
  18. duke37

    Hello! (and Help!)

    Draw two horizontal lines, one at the top of the diagram and one at the bottom. Connect the positive of the battery to the top line and the negative to the bottom line. Find the 555 data and fit it between these lines. Put the output on the right. If you get the diagram laid out logically...
  19. duke37

    Dehumidifier not working - suspect fault in fan motor; easy fix?

    Shaded pole motors such as this run hot and the output bearing can seize. If the motor appears stiff then it may be possible to strip it and clean the bearing. If you do dismantle, rebuild the same way or the motor will run backwards.
  20. duke37

    Repair subwoofer Yamaha YST-SW320

    The Yamaha site has two manuals. It seems you have to log on to download. I do not want to do this.
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