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  1. duke37

    Motors

    Go down to your local scrap yard and get a car dynamo (not alternator) which will make a powerful motor. Speed can be controlled by pulse width modulation and field weakening. The dynamo should be OK to run up to 10,000 rpm without flying apart. I have used a permanent magnet DC motor from a...
  2. duke37

    Shunt Resistance

    Yes, and to shunt (connect in parallel) R1 connect between B and ground.
  3. duke37

    Shunt Resistance

    Neither series or to the ground. To shunt R2, connect the 10kΩ resistor across it i.e. between B and C so that the connection will now be somewhat less than 10kΩ. Resistors in parallel, add the conductances. 1/100k + 1/10k = 1/?
  4. duke37

    Christmas Light Problem

    Some of the christmas tree lights which use series bulbs will short the bulb when the filament fails. Thus the rest of the bulbs carry on working at an increased brightness and shorter life
  5. duke37

    Soldering wire to metal

    The solder moves towards the heat so heat the work and apply the solder to it. Do not expect a blob of solder on the iron to transfer to the work by capillarity. A very small amount of solder on the iron will help heat transfer. Cleanliness is crucial.
  6. duke37

    Computer ATX PowerSupply to Lab Bench power supply

    If your voltmeter has an input capacitor, then switching from 12V to 5V will put 12V on it for a short time. The PSU might not like this. A heavy load might stop this.
  7. duke37

    Time Based Automated Light System

    A simple way of controlling the lights is to use a central heating controller which can be programmed for time and day. Try to find an electrical engineer who does complete rewires, they use new components and old mechanical programmable are often not reused.
  8. duke37

    why connect a jfet gate to source?

    Look up the transistor data for a rough idea. Measure the current for the actual fet that you have.
  9. duke37

    four way traffic lights - help

    A 4017 needs power on pin 16. R6 is connected between ground and ground.
  10. duke37

    Would this transistor work?

    You have connected your transistor as a diode. You need three connections to amplify. What is wrong with buying transistors, they are cheap enough. Are you going to dig up copper ore and refine it?
  11. duke37

    Headphones from amp speaker wires

    A valve amplifier runs on a high voltage and a low current. To make the output suitable for a speaker, a transformer is used to drop the voltage and increase the current. If you are going to run the amp, then follow the instructions, you do not need to know why. The transformer stores energy and...
  12. duke37

    Power supply help wanted with bridge rectifier.

    The KBPC5010is 50A, I could not find details of the QBPC5010. The bridge will dissipate over 1W for every Amp. The heat sink compound needs to be thin and cover the entire contact suface. I made the mistake of using too much compound on an electron microscope water cooled focus supply.
  13. duke37

    Converting 2.4Ghz ---> 63Mhz Serious Concerns.

    Short was obviously a typo for sort. If you want to get some feeling for bandwidth, then log in to the secret nuclear bunker SDR radio where the output of some amateur bands is shown on a waterfall display. You can see the difference beween morse, RTTY, single sideband (upper and lower)...
  14. duke37

    Headphones from amp speaker wires

    If it is a solid state amplifier, then it should be OK. If you are worried, then run the output into a resistor, say 3.3 to 10Ω of sufficient size to absorb the power, connect the phones across this with the 100Ω resistor in series. Then the amp will be running into a defined load and if the...
  15. duke37

    Headphones from amp speaker wires

    A solid state amplifier should be stable with no load. Power (W) = V*V/R so the voltage is 13V maximum. The resistor is series with the phone needs to be high enough to prevent damage. Do what BobK says in #2. I presume that the amp is fitted with a volume control and do not harm your hearing.
  16. duke37

    Converting 2.4Ghz ---> 63Mhz Serious Concerns.

    This is all way beyond my comfort zone even though I have been playing with electronics for 60 years. I do know however that you will hardly get any information with 63mHz.
  17. duke37

    DIY programmable battery charger

    There is no way that the charger shown can manage 40A for more than a couple of seconds. The wire sizes and bridge rectifier seem to indicate 5 or 10A. Edit. Two 6V batteries in parallel will yield 6V.:)
  18. duke37

    carbon steel screw versus brass screws

    I would worry about corrosion in damp conditions such as kitchens or external walls.
  19. duke37

    Pellet Stove Motor will not run

    It looks as if the logo is from Fujitsu, see a resource on logos by KrisblueNZ. The stud is just to hold the capacitor. It may be metric, not 3/8. Any 3uF 400V motor run capacitor should do the job. There are loads of capacitors of this type on the net.
  20. duke37

    Trying to identify and locate component or suitable replacement

    I did not recognise 8Y as a common mode choke. There will be a connection between top and bottom but no short. C25 looks to have a domed top and could be the source of the short. Also investigate C35.
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