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  1. duke37

    Help with AC conversion

    The colours used in the UK are different but the following is what I interpret. The neutral is red except to the fan where it is grey. The compressor is fed from relay contact 3 with a black wire. This is the one to get power from. The fan apears to have two feeds, H and L (high and low?)...
  2. duke37

    Variac Current Meter

    Yes indeed, without the resistor there will be full voltage across the rectifier (which only needs to be low voltage) and meter. Two possible smoke sources.
  3. duke37

    Voltage Signal Circuit Zener

    The current drawn is 10 mA LED (perhaps change scaling resistors) 10 mA relay 10 or 20mA zener depending on whether relay is energised Total 30mA 6.8k at 223V = 33mA, 7.3W zener 20mA at 12V = 240mW, use 0.5W The 1M sense resistor dissipates 50mW only but I would go for 0.5W...
  4. duke37

    what do i need to make a motor timer/controller?

    You do much better with Paintbrush than I can manage. I either sketch the circuit on the back of an envelope and scan it (quick) or use ExpressSCH which is slower, needs to be learnt and gives a neat output. There is an example of both methods that I have used on this thread. Duke
  5. duke37

    what do i need to make a motor timer/controller?

    And a bit worse! You have taken the motor supply from the smoothed source. This will put the interference straight back into the chips and the voltage drop across the 100R resistor will be excessive. Connect the motor supply directly to the input voltage. Duke
  6. duke37

    bike light circuit advice

    1. I think that you should measure the voltage coming from the generator to see if things are of the right order. 2. The capacitors are not necessary. LEDs can take a rough supply. 3. The zener may overheat if you have too much breakfast. 4. A resistor instead of the diode will limit the...
  7. duke37

    what do i need to make a motor timer/controller?

    You are getting there. The power to the 555, pin 8 should come from the supply smoothed by the capacitor, not direct from the input. The 10k feed resistor seems too high to me. Steve suggested 100R. Duke
  8. duke37

    Variac Current Meter

    The voltage measurement is good. Chose a high voltage low current bridge. The current measurement is wrong. As drawn, there would not be enough voltage across the resistor to turn the rectifier on. You must put the resistor across the + and - terminals of the rectifier. All the current goes...
  9. duke37

    what do i need to make a motor timer/controller?

    You are making life complicated! You do not need the 2N3904. You do not need power to the FET, it is just like a switch in this application controlled by the voltage on the gate. The power for the motor comes from the 12V source. The diode should go across the motor, you have shown it...
  10. duke37

    what do i need to make a motor timer/controller?

    1. The output from the 4017 is wrong, either the relay pin 86 should go to earth or you should use the use the circuit in the previous post. 2. The 470R resistors will severely restrict the motor power, is this what you want? 3. It would be simpler, smaller and probably cheaper to use a...
  11. duke37

    Vacuum Tube Amp

    As a starting project, a 10W amplifier is a bit ambitious. All the tubes you mention are triodes designed for amplification and would give out less than a watt. To get 3 or 4W you could go for a single 6V6 or EL84 with a suitable ratio of transformer. You say that no amplification of the...
  12. duke37

    what do i need to make a motor timer/controller?

    Do you have one motor or a plethora? I attach a diagram of a traffic light sequencer which I made recently, this shows the basic idea. You will need to alter the timing on the 4093 oscillator to suit yourself and you will not need any of the 1N4148 diodes, just take an outout from the 4017 to...
  13. duke37

    class C bias question

    Well done, you have it. There is no resistance specified for the IF circuit and in any case, the current is zero as you determined.
  14. duke37

    adjustable amplified BJT circuit..help

    You have not specfied where the output is. I assume that it is across the 10k load resistor. I do not see how to calculate the resistors, it could be done if you have a resistor in the emitter connection of the transistor. Have you got the circuit right?
  15. duke37

    what do i need to make a motor timer/controller?

    Have a look at the CMOS 4017 Johnson counter, this could be clocked at 2 second intervals and the outputs could switch MOSFETs to drive the motors.
  16. duke37

    magnetism.

    It all depends on what you define as ground. In the UK the neutral is connected to ground at each house and all central heating and gas pipes are strapped to this. The idea is that everything in the house is at a common potential so not a shock risk. This potential may not be at exactly ground...
  17. duke37

    Noise from amp

    If your 40W amp is rated as output, it will need about 80W input or 7A. Pity your poor little PSU. You will need to go for a much bigger PSU. Measure the voltage as each part is connected, starting with the radio. Duke
  18. duke37

    class C bias question

    You seem to have the answers, why not give them here?
  19. duke37

    class C bias question

    You are asked for the DC conditions. What is the voltage on the base? What is the current into the base? What is the resultant collector current? What is the voltage drop across R3? Subtract this from 12V to get Vc. Remember Ohms law, V = I * R Duke
  20. duke37

    Oversized VU meter simulation for exhibition stand

    You could use a small electric motor, belt or string driving a large pulley with the pointer attached. The pointer shaft would have a potentiometer attached to give a variable output voltage. This could be fed to a LM3914 display driver to give up to 10 outputs as required. The mechanical...
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