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  1. duke37

    What battery to use for RF receiver

    I looked at the link and it cocked up my computer.
  2. duke37

    a/c led indicator circuit

    Yes, the diode can go across the LED or the entire circuit. The 33 ohm resistor controls the current through the LED from the voltage drop primarily produced by the 100 ohm resistor. Don't forget the 33 ohm resistor. If the diode is placed across the entire circuit, the dissipation will be...
  3. duke37

    a/c led indicator circuit

    Perhaps it overheated because it was so small! 62.5mA through 680 ohms dissipates 2.6W. Why not try Resqueline's circuit with only 100 ohms. Your diodes are plenty big enough.
  4. duke37

    Voltage Signal Circuit Zener

    I attach a diagram of what I thought could work. The voltage is divided by 50 to make 250V=5V at the chip. Making the reference 5V supplying the resistor chain and placing a 40k resistor to ground, gives a range of 4V to 5V which would indicate from 200V to 250V. Since there are 10 LEDs these...
  5. duke37

    a/c led indicator circuit

    Normal LEDs take a maximum of 20mA but you could use multiple ones or a current sharing resistor. A diode would be needed to prevent a reverse voltage appearing on the LEDs on the 'other' half of the cycle.
  6. duke37

    a/c led indicator circuit

    The neon will take far less current than the bulb so the bulb will not light up. The current the bulb takes is about 62.5mA. If you put a low voltage bulb (6 0 or12V) in series with a rated current of 100mA it should work, otherwise make a window.
  7. duke37

    Unwind two wraps of toroidal transformer?

    Looking at the board, I see only one winding. I think this may be a smoothing choke a turn or two less may not make much difference but there is plenty of room to put a turn or two on.
  8. duke37

    Triangulating Location

    The TV shows repeats of sports events using Hawkeye to show the path of a ball. I have no idea of the technology involved
  9. duke37

    Voltage Signal Circuit Zener

    The weather is nice here at the moment so I should be out in the garden. The LM3914 should be supplied with about 12V with a resistor and zener. The internal reference voltage is low but they provide a means of raising it with an internal op-amp and resistors. I would set it for something less...
  10. duke37

    Voltage Signal Circuit Zener

    You will need a resistor and zener diode (12V) to provide a power supply for the chip and a voltage divider to provide a sample of the measured output voltage. When they say that the LED current is programmable, they mean it can be set. This is done with a single resistor. If you go for the...
  11. duke37

    Voltage Signal Circuit Zener

    Look at the LM3914. This is a LED bar or dot driver, it contains a voltage reference and ten comparators. An indication of battery voltage could be given and, when the last LED is lit, a small amount of current could be taken and amplified to switch your relay.
  12. duke37

    Best Infrared beam emitter and sensor?

    I doubt if the wavelength is important, just get a matching pair. However, there will be a problem with ambient light. This can be alleviated by switching the led at high frequency and then filtering the received signal at that frequency (sychronous detection?). Duke
  13. duke37

    LED Switching/activation

    To activate a switch through glass fibre, you should consider using a reed relay and a magnet. Some experimentation would be needed to make sure that there is sufficient magnetic material around to prevent the magnet falling off or a clip could be made to hold it on.
  14. duke37

    Bridge Rectifier help

    As shrtnd says, four diodes can be used to make a bridge. The KBPC110 is 1000V 3A and four !N5408 diodes (1000V 3A) would do the job. The diodes are meant to be cooled through the leads so should be soldered to a substantial terminal if to be used at full current. The bridge rectifier is cooled...
  15. duke37

    kitchen hood: Problem wiring my power-open damper.

    The wiring is a loop and a switch at any point in the loop will turn the current on and off so it will work with the mains connected either way round. It is safer to put the switch in the live line as shown in your first diagram. Did you wire up the power plug yourself? In the UK the wiring...
  16. duke37

    Triangulating Location

    You can use sound waves to generate longer time intervals. Sound ranging was used in the first word war to determine the position of the enemy's guns. Pity the poor sod who had to go out with the microphone on the end of a wire. I believe that the same thing is done these days with microphones...
  17. duke37

    A Security Gate For a HND Mechatronics Project

    Temporary traffic sensors in the UK use a rubber tube filled with liquid and attached to a pressure switch. A good rubber tube may that will withstand traffic may be hard to find. Pressure switches abound, you could get an oil pressure switch from a car scrap yard. Permanent trafic sensors...
  18. duke37

    kitchen hood: Problem wiring my power-open damper.

    I can not get at your second link. Do not go into the motor, you will find nothing of use there and may cause damage. The windings and capacitor should be treated as one unit and not be fiddled with. I do not know what your motor consists of but it seems to be similar to a central heating...
  19. duke37

    Need Help! About the LED light.

    I do not understand why it is so complicated, surely it would work with C1 only as the current setting component, disconnect R3 which shunts useful current and short R2. Remember that the circuit is live and will bite. Duke
  20. duke37

    Variac Current Meter

    If you are using a single meter, it would have a cleaner display wih one scale. If you chose 0 to 15, the resistors will need to be changed to suit.
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