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  1. duke37

    5 volt solenoid

    The TIP102 has a diode to prevent reverse voltage across the transistors. It does NOT have a diode to protect the device from exess voltage. For this you need a diode connected across the solenoid in a direction that does not normally conduct. Alternatively you can connect a resistor across the...
  2. duke37

    add light to 1930s fuel pump

    It is a long time since I had to thump an SU fuel pump to make it work. As I understand, the contacts are closed when the fuel pressure is low and a stroke is initiated to pump some fuel. If the pressure is not sufficient, this will be repeated and the pump clicks at a few times per second...
  3. duke37

    Parmak Mod 6 Electric Fence Charger

    If you are grounded and get a shock by touching a ground rod, then the rod is not doing its job or the ground has very high resistance. Try a new ground rod in a different place. In the UK we would use maybe a one foot ground rod but then it rains here. You could test the charger feeding...
  4. duke37

    Need a bit help in understanding effect of resistors in circuit

    It would be better if you used standard symbols for the components. Also the curves are not labeled.
  5. duke37

    Need a bit of help with a 12V 10A SMPS design using TL494

    I have looked up the data sheets of the transistors, they are nothing special. NTE153 90V -4A 8MHz NTE331 100V 15A 3MHz You can google for equivalents. The frequency of switching is important since the transistor dissipates quite a bit of power during the switching time when there is...
  6. duke37

    Need a bit of help with a 12V 10A SMPS design using TL494

    My old book does not cover the NTE153 and NTE331 but these seem to be nothing special. My notes of transistors that I have show the following types. pnp driver 2N1132 BFX29 BFX30 npn power, heat sink needed. 2N6099 2N3055 BDY20 A p-channel fet could be used with a couple of...
  7. duke37

    Changing a motor's direction each time power is supplied

    That looks better from a motor point of view. Remember that the start winding will have a series capacitor. I do not know anything about the impulse relay. but you must ensure that the motor is not 'started' when it is aleady running in the other direction.
  8. duke37

    Changing a motor's direction each time power is supplied

    The motor will have two windings, one with a series capacitor and four wires. One winding will need to be reversed as shown in the diagram but the other winding will need to stay the same.
  9. duke37

    Modifying 110v device to run on 240v

    One way of reducing the power of the element would be to use phase angle control, like a light dimmer but MUCH fatter. The peak current will be very high, the radio interference could be severe and fuses/trips may object.
  10. duke37

    Rotation Switch

    Do you mean 'slows down' or do you mean stop. An analog output tachometer can have its signal differentiated to set a bistable on speed up and reset on slow down. The rate of speed up and slow down will need to be defined.
  11. duke37

    Modifying 110v device to run on 240v

    You would need a very large and expensive capacitor for this power. Use a transformer, also large, expensive and heavy. You could use a series resistance but this will dissipate the same power as the device unless the diode bodge is also added.
  12. duke37

    How does this LED driver work?

    A half wave rectifier takes either the positive or negative part of the waveform so produces pulses at the same frequency as the AC input. There is a DC component to the current in the transformer which the transformer may not like. A bi-phase rectifier uses a centre tapped transformer...
  13. duke37

    How does this LED driver work?

    You can use a LM317 as a constant current supply, you do not need a stabilised voltage to feed it. Watch the power dissipation and provide sufficient heat sinking.
  14. duke37

    Uk users, where so you buy your components from?

    Or try cpc.co.uk, a part of Farnell I buy common components from R.F. Potts in Derby (no website) or Bowood in Chesterfield. Crcklewood Electronics seem to have a wide range of components but I have never dealt with them.
  15. duke37

    Variable DC supply circuit - any critiques?

    Try a car battery charger on 12V to get an idea of the glow. If you have a tame friend with another battery charger, you could put them in series to see what it looks like on 24V. You seem to think that DC is safe. I am not so deluded.
  16. duke37

    Slip ring wear

    My brother has a three phase generator which was involved in a fire. I replaced burnt out wires and a three phase rectifier. It works, glory be ! I have noticed that one slip ring is badly worn and the other is almost like new. I assume the difference is due to the different polarity. I would...
  17. duke37

    Capacitors and Leds

    The capacitor should provide the power to the constant current supply. I get different values to Arouse 1973. Voltages led 3V resistor 0.5V regulator reference 1.25 regulator drop out 2V Total 6.75V So, from 16V, you have about 9V to play with. Discharge of a capacitor dv/dt = I/C...
  18. duke37

    Capacitors and Leds

    Use a constant current supply. This can be made with a constant voltage regulator, connected differently. Set for 70mA and put a lowish value resistor (470) in series with each led to make sure the current is shared fairly. Power will be lost in the regulator so you will need a bigger capacitor.
  19. duke37

    Capacitors and Leds

    I do not think you need a Schottky bridge, any diodes will do. I do not see how a regulator would be a benefit. Some rough calcs, I'v oiled my abacus. 7 leds at 10mA = 70mA Each will have a resistor but calculate the lot in parallel. R = 13/0.07 = 186 Time constant = 10 sec = R*C C =...
  20. duke37

    Frequency Detector

    Obviously, the cleaner the signal into the 567 the better. It is a long time since I read up about the 567 but I remember that one of detectors will lock onto harmonics. This you do not want. I suggest that you chose the best detector for your purposes.
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