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  1. duke37

    High-voltage failsafe?

    There are so many variables that it is impossible to be specific. You do not know what current your heart will take before it decides to take a rest. The idea that a 15A supply is safe is a delusion, it is no safer than a 100A or 1000A supply. The reason that novices are not allowed to work...
  2. duke37

    TO-220 heat sink electrical isolation

    The red wire looks to me to be insulated with thick insulation. High voltage can punch through this but 400V would not be enough unless it is damaged.
  3. duke37

    How do you increase IR LED range?

    "More adventures in optical communications." Stuart Wisher RadCom May 2012 p40 Two way contact 117.6km Wavelength 630nm Other wavelengths used 850nm and 940nm 55km has been achieved in daylight using Phlatlight leds at 5.9A. There is a Yahoo group UKNanowaves.
  4. duke37

    How do you increase IR LED range?

    The RSGB in RadCom published some articles on IR range. With very sophisticated equipment, they managed several km. It was done at night and a telescope was used with lights to line up the sender and receiver. I may have a look at the annual indexes if I have time.
  5. duke37

    Sand rail glowing spark pugs...

    As I suggested, you could use a 4017 to provide a walking display, driven from one plug only so that persistance is less of a problem. If the 4017 outputs are put into a 4013 or 4027 divider, the led will be on for 50% of the time so will be much brighter. It looks as if Mongrel Shark has got...
  6. duke37

    High-voltage failsafe?

    I think you are wrong to think that 120V AC is safe. If the current path is across the chest and if the hand clamps on the live component, then something will give. I had a friend who had a hedge trimmer (240V) and he touched the plug when the top had dropped off. His hand clamped on. He said...
  7. duke37

    Sand rail glowing spark pugs...

    You should consider the rate at which persistance of vision becomes a problem. You may want to use just one plug and use a Johnson counter (4017) to give a walking (running) display. An intermittent light at more than about 30Hz will appear to be on continuously.
  8. duke37

    Multi-voltage step down

    Wikipedia gives details of computer power supplies. These will give 12V, 5V and 3V. The 1.2V could be almost supplied with a LM317T 1.25V regulator from the 5V supply.
  9. duke37

    How do you increase IR LED range?

    As GG says, overpowering a led is not good. You could use a lens to focus the radiation on the receiver. This could be a plastic Fresnel lens which is flat and lightweight. You will need to get a lens which will pass IR radiation. This type of lens is sometimes used in the rear window of a...
  10. duke37

    Sand rail glowing spark pugs...

    What is a sand rail? The spark can be detected with a small capacitance to the plug lead. Some experiment will be necessary. The pulse could go to a fet to turn on a led. The main problem will be getting sufficient pulse which does not blast the fet to oblivion, a good protection circuit...
  11. duke37

    Solenoid Alarm Clock in Series -- Voltage Problems –Amplification

    The St Andrews University link did not work for me. The sparkfun link was not too clear but I think the solenoid has a resistance of 19 ohms. The power is therefore not minimal. You will need to detect when the alarm clock goes off and then use it to switch a power supply to the solenoid...
  12. duke37

    AND and NAND chips

    I do not know if the list is correct. It seems to be the same list as gorgon linked to. Data links are given for each chip to check, only 200 to go. I tend to use CMOS as it uses less power and is less fussy about power supplies.
  13. duke37

    Help bluing razor blade

    WWII razor blades were made from carbon steel and rusted very quickly. Present day blades are made from stainless steel and rust very slowly so will last longer if not used for chopping wood. The oxidation at high temperatures will be very different with different surface oxides. A blade...
  14. duke37

    AND and NAND chips

    Wikipedia do a list of TTL chips.
  15. duke37

    Repairing a 1937 GE cathedral super het

    You damaged an amp by overdriving it and now you have severely damaged this radio set. A loopstick antenna seems to be very unlikely for a 1937 set. How many sections are there in the tuning capacitor? Can you find a model number? There are 8 tubes but what are their numbers? Do not unplug...
  16. duke37

    Adding a pot to a hot air gun to control airflow

    I have only looked at two heat guns, both of these had the heating element in series with the motor. The motor was of the universal type (series rotor and stator) and low voltage. Thus when the heat is turned down, the motor slows. If your gun is of this type, then leave it at full output...
  17. duke37

    High-voltage electrostatic power supply and meters

    Fly zappers use a very high voltage, I do not know how high. Colour CRT TVs use a high DC voltage, maybe 20kV? You may be able to use a TV line output transformer. A Cockcroft-Walton multiplier can generate a very high DC voltage from a high voltage AC signal. Voltage dividers can be...
  18. duke37

    Could you help on interpreting part of a circuit?

    The 1/50 could be a 1uF 50V capacitor but the blury symbol looks more like a diac which is not likely. BP = BiPolar???
  19. duke37

    Transistors as switch

    And here is the rest of the circuit.
  20. duke37

    Transistors as switch

    Instead of changig the frequency of the oscillator, you could use two oscillators. I think a 4093 can do the job as shown. The frequency of an oscillator will be 2.7/(R*C). The line marked A will be needed to switched from hight to low to change the frequency. A resistor in the output will...
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