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  1. duke37

    Simple LED circuit for complete noob

    Here is an idea. Duke.
  2. duke37

    kitchen hood: Problem wiring my power-open damper.

    The motor speed is likely to be controlled by resistors. The common terminal will be 3 black and the other connection to the motor will be selected down to 9 blue. The resistors are located in the motor housing so that they are cooled by the air flow. An alternative would be tapped motor...
  3. duke37

    Beam breaker not triggering relay

    The relay coil has a resistance of 100R, at 6V this means 60mA. The relay in series with 240R will take 26mA (2.6V) on 9V - not enough. The specification says 4.5V minimum on the relay, with 0.7V acoss the emitter/base of the transistor, you need 5.2V on the base. If you use a low value...
  4. duke37

    kitchen hood: Problem wiring my power-open damper.

    I do not fully understand your description. However, you need two wires to a switch. Should the white line in go to the switch and a white wire from the switch go to the gubbins? The switch will then turn everything off.
  5. duke37

    Variac Current Meter

    I presume that the meter is a DC type. Voltage At 140V, the average voltage is 140*0.9 = 126V To get 104.5uA you need a resistor of 1.2M, also a bridge rectifier. A capacitor should not be necessary unless the meter vibrates. If you rectify first and fit a capacitor, the voltage will be...
  6. duke37

    Courtesy

    Hi Dave You seem to be dismayed that your posts are not aknowledged. The forum is open to all and nuggets of wisdom can go to others who do not appear on the thread. I often look up the interesting links which you post but I spend too much time looking at the google box and do not make a...
  7. duke37

    Pfaff 1471 sewing machine

    The motor is probably fitted with brushes which can wear out. Try measuring the resistance across the motor terminals and see if it changes when the motor is turned by hand. Was the sewing machine plugged in when the strike came?
  8. duke37

    connecting 2 transformers

    Two transformers instead of one has the disadvantage that if they are to feed a diode rectifier, there will be a net DC current in the transformer giving the possibility of core saturation. If you want a +/- DC supply you might be better using a bridge rectifier on each transformer and then...
  9. duke37

    Adjustable Current and Voltage Lab Supply. LM317

    I bought a power supply from a radio amatuer junk sale giving dual variable voltage and current. Surprisingly it worked! I have no idea how old it is. It contains a pair of L200C chips which control current and voltage.
  10. duke37

    Volts, hp, & Hz to Amps?

    1 BHP = 746W, horses can vary somewhat. 0.5 HP = 373W Current = Power/ Voltage = 373/120 = 3.1A Motors take a lot more current to start than to run so I would be inclined to go for a 10A relay.
  11. duke37

    How to make a RLC circuit with Op-amps?

    It depends on what you want to do! Op-amps can be used to substitute for inductors but using more capacitors. I have never done it but have seen it described in "Electronic Filter Design" by Arthur B. Williams, there is a later book by Arthur B Williams and Fed J. Taylor also. The circuit you...
  12. duke37

    tachometer.

    The capacitor on pin1 smooths the input signal to stop spurious triggering, it is a compromise. The original reference specifies 22nF and you have used 100nF so it should work at low revs but maybe not at high revs. The capacitor on pin 2 affects the output volyage, they recommend 47nF and...
  13. duke37

    Measuring ballast output

    I would go for the current transformer solution to isolate the scope from the mains. Take a mains transformer and feed a single turn around the bobbin, put a 100 ohm resistor across the old primary and measure the voltage across that with the scope.
  14. duke37

    Creating a battery pack for this?

    Reading the data on the site you have given, it takes up to 5W but needs 12V at 1.2A which is 14.4W. The heavier the load, the greater the current taken. A 12V sealed lead/acid battery should do.
  15. duke37

    26 way socket

    Moist is all relative. It has been fairly dry most of this harvest and the grain has been 16% or so. This will keep for a short while. For long term storage it is necessary to go below 14% or store in a sealed silo to restrict oxygen. In poor conditions the grain can be up to 20% and the combine...
  16. duke37

    Transistor as switch (newbie question)

    Would something like this do? Micro high would be off and micro low would be on. If this is not convenient, another transistor could be added.
  17. duke37

    26 way socket

    Thanks for the reply Steve. I have loked at all the usual suspects (suppliers) with no success. A friend of mine said 'Ah yes, we used those many years ago'. The makers of the meter was sold (to GE) and the company who took over the bits do not have any sockets or main boards. The current...
  18. duke37

    26 way socket

    I have been given a Protimeter Digital Grainmaster to repair. This has a socket to take a calibration card for various grains. The unit was dropped, but nobody dropped it! The calibration card has split the socket and I wish to replace it but cannot find another. It is a 26 way with concacts on...
  19. duke37

    What power cord?

    According to my old Maplin catalog, there are two varieties of DIN 8 pin connector, this looks like their FJ91Y.
  20. duke37

    Gold Plating... Is it worth it?

    Early transistors were supplied with gold plated leads but these were found to produce unreliable solder joints.The soldering was very easy but an intermetallic gold/tin compound was formed which was very brittle. See Wikipedia.
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