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  1. duke37

    Signal Generator????

    If all you want is a voltage source 0 to 10v in steps of 1V then you can use the attached circuit. It should be possible to trim it to about 1% accuracy. Is this what you want?
  2. duke37

    Signal Generator????

    What is a VFD, vacuum fluorescent display or variable frequency motor drive? If you want to test a voltage input, all you need is a battery and potentiometer and a voltmeter to measure the voltage. The 4-20mA input looks like a curent loop and would need a variable resistor in series with a...
  3. duke37

    Transformers

    Consider a hammer, if a force is put on the hammer, it accelerates. Force=mass * acceleration. The kinetic energy in the hammer = mass * velocity squared/2. If the hammer now hits a nail (preferably one without a thumb attached) then the deceleration is rapid and the force is high, usually...
  4. duke37

    How do I use a push to break switch to turn something on?

    If the lamp is low voltage, you can drive this with a transistor. The base of the transistor should be connected to the positive supply through a resistor and your switch should be connected between base and ground, thus, when the switch is opened, base current flows and the transitor turns on.
  5. duke37

    project: traffic loop car park barrier

    You could use a high pass filter (or low pass filter) so that when the frequency gets high enough (or low enough) then it passes an output. This could be rectified and used to power a relay or fet to switch the motor. There are also frequency to voltage chips which could be used (LM2971N)...
  6. duke37

    DIY UPS unit?

    I am no expert on inverters but square wave inverters will be more efficient than sine wave inverters. Square wave inverters are kind to rectifier input devices. Your pump probably has a shaded pole motor which may get hot with a lot of harmonics. Parts for a square wave inverter would cost...
  7. duke37

    design of a power supply

    Davenn has shown the way to connect the bridge rectifier correctly. The arrows depicting the diodes point to the positive output. The arrows point away from the negative output. The other two connections are the AC input. Try following the current path with the current in the transformer going...
  8. duke37

    DIY UPS unit?

    Inverters vary from simple square wave (easily made) to accurate sine wave (expensive). Your pump may not like a square wave inverter with its high harmonic content. Have you considered a 12V DC pump, you will not then need an inverter?
  9. duke37

    design of a power supply

    Comments. 1. You have the rectifier connected incorrectly, this will short the transformer. 2. The led will be very bright for a millisecond. Look on this site for details of how to drive a led. 3. The rate of voltage change on a capacitor, dV/dt, is I/C. Time is 1/120sec , current (I) =...
  10. duke37

    Another Question for those who are better with transformers

    To see if you are still confused, assume it is a 25-0-25V transformer tapped at 9V, what voltages can you get out of this? If you use bi-phase rectification with 1V diode drop and storage capacitors, what peak voltages can you get?
  11. duke37

    Another Question for those who are better with transformers

    The black is the odd one out with no butty. This is the centre (US center) tap with 9.7V to each blue and 27V to each red. The voltages will be double red/red and blue/blue.. The voltages will drop somewhat under load, perhaps by 10%. It is probably a 25-0-25V transformer with taps at 9-0-9.
  12. duke37

    wiring pid controller circuit

    I have had another look at your picture, as far as I can tell it says 80A which is the current carrying capacity and 30mA which is the earth leakage trip level RCCB means residual current circuit breaker.
  13. duke37

    wiring pid controller circuit

    Is that the one with the red button which probably says test? There should be a label saying the fault current for trip, probobly 0.03A. If this is the one which has tripped, then you have earth leakage on your furnace. You could try blowing into the furnace with a fan heater to dry the bricks...
  14. duke37

    Basic beginners mistake?

    Two comments. 1. The measuring of the resistance will affect the resistance and the dissipation in service will give an offset. 2. Start without the feedback resistor to give instant switching and then add the resistor and decrease its value to give the deadband required. I used to service...
  15. duke37

    Basic beginners mistake?

    The deadbug technique uses a sheet of copper (PCB) or tinplate and glueing the integrated circuit on it with its legs in the air. Other components are soldered in free air. You may wish to make a pad or two out of plain pcb. The result is not pretty in my case! I have made a vibrator...
  16. duke37

    wiring pid controller circuit

    You have not clarified whether the trip was due to overcurrent or earth leakage, this must be done. If your welder blows a fuse before the trip goes off, then you are likely to have an earth leakage problem with the furnace. To get under the 13A limit, you will need another 5 ohm of wire but...
  17. duke37

    "Lafayette" LSG-10 Signal Generator

    There are two outputs, one audio frequency and is fixed and one radio frequency which is variable in frequency and can be modulated by the audio frequency. I assume that you are looking at the audio output. you can check the RF output with a radio placed nearby and swinging the tuning till the...
  18. duke37

    Basic beginners mistake?

    You appear to have a contaminated board so increasing the 1M resistor may not do much. It was suggested on a previous post that an alternative would be to reduce the 10k resistors. Leakage through contaminants would then have a smaller effect. Reduce the 10k resistors to 1k, this should...
  19. duke37

    wiring pid controller circuit

    I have had a look at the mains specification, it can go up to 253V. 253/15 = 16.9A 253*16.9 = 4267W The garage is likely to be a on a fused spur and will be not happy with an overload. I suggest that you need to install a dedicated circuit and the regulations state the it must be installed...
  20. duke37

    wiring pid controller circuit

    Your latest picture shows a curly wire top right, I thought this was part of the element, apparently not. Your equations are right but you have started at the wrong end, you have relied on the supplier giving you wire to the exact specification, wire can differ a bit in diameter and resistance...
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