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  1. BobK

    Need help in designing switching/chopping circuit

    3A at 100V to operate a reed switch? Bob
  2. BobK

    Amber and White LEDs

    Any electronic supplier would have them. Depends on where you live. Bob
  3. BobK

    Do I need a voltage regulator in my LED circuit?

    I was referring to the fact that the sun is a pretty good grow light all by itself. Bob
  4. BobK

    TIP122

    Agree. Having the lamp at the emitter is providing negative feedback to the base. The more current the lamp draws, the higher the emitter voltage and thus the higher the base voltage must be to turn on. Bob
  5. BobK

    Do I need a voltage regulator in my LED circuit?

    I can sell you a 100% efficient solar powered grow light at a good price :) Bob
  6. BobK

    LED grow light help

    There are 3 and 5 Watt LED out there that can produce hundreds of lumens each. You would want to search for the most efficient (lumens / watt) LEDS you can find in that range. And they require drive currents of about 1 Amp at about 2.5V for the red and 3.6V for the blue. You would want a...
  7. BobK

    LED grow light help

    That's the understatement of the year. I calculate a total output of about 5 lumens. For comparison, a 100W incandescant bulb is about 1700 lumens. You will need much more powerful LEDs for a grow light. bob
  8. BobK

    Tripwire "mine" for CCF

    That sounds like a fun project. For a "sensor", how about just using two springy metal contacts that would normally touch, and inserting a piece of plastic between them tied to the trip wire? I think you could make this quite sensitive. For an inexpensize way to get a loud sound look up...
  9. BobK

    final year project based on andriod

    This is too tempting, but I am not going to go there :D Bob
  10. BobK

    LED Proximity to MIDI Interfacing modulated ir to a control voltage (0 to +5)

    Google "IR remote control module". You can get receiver modules that are 3 pins and include all the filtering needed. You supply power and ground and the other pin is an ouput that is high when it is receiving a signal. The transmitter is just an IR LED fed by a square wave. The typical...
  11. BobK

    how to manually clock a 74163 IC?

    Wow, $4.15 for an IC to debounce a switch! For about 1/4 of that you could get a PIC microcontroller that would replace all of your chips, debouncing the swiches, implementing the counter and decoding and driving the display without any additional components except resistors on each segment. Bob
  12. BobK

    dc-dc step up circuits in series?

    Well, at 100% efficiency, your first battery would last 21 minutes and your second would last 36 minutes. Realistically, multiply these by about .8 to get 17 or 29 minutes. Is that what you are expecting? Bob
  13. BobK

    Basic question - Led power supply

    The best way to drive an LED is with a current controlled power supply. There are LED drivers available that do this. Try dealextreme.com for very cheap drivers. You do have to wait about 2-3 weeks to get anything from them though. Bob
  14. BobK

    Beginner - need help with simple led design

    If you turn on only 1 light in your house is it 10 times brighter than if you turn on 10 lights? Of course you can run 15 LEDs off a single power source. Each will need it's own current limiting resistor. And the power supply must be able to supply enough current when all of the LEDs are...
  15. BobK

    how to charge those capacitors please ?

    The first thing you should learn is that working with dangerous voltages is not the first thing you should learn. Bob
  16. BobK

    how to charge those capacitors please ?

    All I will say then is please err on the safe side, so that instead of killing someone, your attacker is only angered a bit more and it is you who suffer the consequences. Bob
  17. BobK

    how to charge those capacitors please ?

    And how do you propose to test this? To make sure that it has stopping power without being lethal? I am not a beginner and I would not even think about attempting such a project. If you succeed in creating the voltage / current needed, you are VERY likely to hurt yourself or someone else...
  18. BobK

    Need help finding a solution - switch / Help for a noob - relays

    You could use a 3PST switch to achieve this: o----/ o-----+ | o----/ o-----+ | o----/ o-----+ Connect your three wires to one side of the 3 switches, and connect the other side of the three swiched all together. Bob
  19. BobK

    using of regulator

    Conductor3's circuits are missing required capacitors on the input and output. A datasheet will give you the correct circuit with the reccomended capacitor values. Bob
  20. BobK

    Help on transistor design

    If you put the load between the collector and V+ and the emiiter to ground, you can operate an NPN switch as follows: Connect the base through a resistor to the input voltage, which must be greater than 0.7V. The resistor is chosen based on the desired current through the load and the beta of...
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