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  1. duke37

    linear analog servo motor drive

    If you want position control you will need some form of feedback to determine the position. Many years ago, model aircraft used potentiometers to indicate position. I do not know current technology in this area. A potentiometer can be used to provide a voltage to match that of the input when the...
  2. duke37

    Log In

    Ticking the little box seemed to have sorted it. Thank you for your help.
  3. duke37

    Generator Cutts out when Load is applied

    Has it worked in the past? A motor will take much more current on start than when running and the generator will need to supply this peak.
  4. duke37

    Log In

    I have been on the forum for two or three years without problems. Now I have to log in each time I arrive and if I start to post a reply and then go to look up some data, the first part of the post has disapeared and I have to log in again. If I do not log in, I get several advertisments...
  5. duke37

    linear analog servo motor drive

    That circuit looks OK. You will need a power supply of about +-7V to limit the motor voltage to 6V. I have not looked up the data for the amps you mention but I have used a LA6500 (1A Maximum) for non audio purposes. The DAC must be able to produce positive and negative outputs or you will...
  6. duke37

    OpAmp Questions

    1. You can not get more volys out than the power supply and it seems that with that particular op-amp, you will only get to within a volt of the power supply. 2.Inverting amp Yes, you messed it up. The feedback must go from the output to the - input. 3. Comparator Once again you are...
  7. duke37

    Working on getting a Pierce Oscillator to Oscillate

    They may have few components but are quite complex. The crystal and choke do not have all their parameters given so it is difficult to simulate. The gain must be adequate to compensate for losses and the phase must be right. The fact that there is a plethora of designs indicates that some...
  8. duke37

    A guitar amp build

    I think you should be OK to connect the two outputs in parallel as long as there is no feedback. The output impedance of a valve amplifier is high and the current supplied by one will not affect the other. If there is feedback, the output impedance will drop, the amplifier will want to set a...
  9. duke37

    Working on getting a Pierce Oscillator to Oscillate

    At 1Mhz, there should be a healthy carrier on a medium wave radio at 1MHz or 300m. 3V supply may be a bit low, you could try 6V.
  10. duke37

    Op Amp Unit Gain at frequency 1 MHz

    Different op amps will have different gains at 1MHz. The gain drops as the frequency rises, you will need to go to the data sheet for the particular op amp you wish to use. I think that the frquency response is due to the inherent capacitors in the active devices. To get a high frequency op...
  11. duke37

    led heartbeat

    The circuit refered to in #14 The 4017 has its outputs almost shorted to ground. This may be too much for it. Put a 1k resistor in the outputs to limit the current. A capacitor across the power supply would not be disadvatageous.
  12. duke37

    design of a power supply

    Would you design a house if you did not know what a brick is? 'The Art of Electronics' contains many circuits which can be modified for your own use. To get twelve independant outputs, use twelve wall warts. If the outputs do not need to be independant you could take twelve outputs from a...
  13. duke37

    12dcV to 2dcV? (car battery to +220 LED's)

    The leds can be connected to the tail light circuit where the relay would be. About 1A extra should not be a problem and you will have a fuse in the circuit which will reduce the chance of fire. You will need to connect the leds correctly so strike while the iron is hot.
  14. duke37

    12dcV to 2dcV? (car battery to +220 LED's)

    Your circuit is not suitable. Leds or zener diodes should not be placed in parallel since one may take all the current until it pops. I would suggest that you place four leds in series to give 8.4V. The excess 3.6V can be dropped with a 180 ohm resistor passing 20mA. You will need 55 strings...
  15. duke37

    Modding a circuit

    Q1 is a virtual earth amplifier. The DC conditions are set by the emitter and collector resistors in series and by the feedback resistor. The emitter resistor is only 1/20 of the collector resistor and should be eliminated. The necessary feedback resistor depends on the gain of the transistor...
  16. duke37

    Induction Heating

    You could try an induction hob but would need some good thermal insulation over the hob, perhaps mica sheets. The hob will only work effectively if the load is magnetic. Iron loses its magnetism at about 770degC. This is above the melting point of aluminium so it may work. You will need an...
  17. duke37

    Induction Heating

    I looked up the electric supply in the Azores, it is 50Hz and is at 220V. The system is small so the frequency may vary a little. I hadn't thought about an induction hob, this will run at much lower frequencies than what I was talking about and works because the load is magnetic, giving...
  18. duke37

    Induction Heating

    What country are you in? The mains will NOT have a frequency of 50 to 60Hz. That will be the tolerance of some device you have found. Induction heaters are essentially high power radio transmitters. They were usually single valve triode oscillators with the tank coil surrounding the object...
  19. duke37

    PA System Problem

    I would think that there may be some value in the amp. The valves could be worth something and if the output valves are SP25s you could go on holiday! I would try an auction website, you have nothing to lose. I have an amp here with a couple of EL34s in the output. You could have this at a...
  20. duke37

    magnaflux device

    I would think that you could make a magnetic from U shaped transformer laminations. The bigger the device the more power will be needed. I think that DC would be better than AC. Where would you get your filings from. Dye penetrant. You could try red ink, possibly with some added alcohol (if...
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