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  1. BobK

    Urgent Help needed to get output of ac 5v 400hz frequency and current 500ma

    Find a 5 Watt audio amplifier that runs at 12V with differential inputs, and wire it up as a Wien bridge oscillator. (haven't tried this, don't know if it would work or not) bob
  2. BobK

    Simple Voltage Controlled Fan Switch

    Unless you are equipped to make a PC board, you would probably do better to buy the kit. How much are they asking? Bob
  3. BobK

    sort of an odd situation

    Calculus, linear differential equations, linear algebra, vector calculus. Maxwell's equations, which are the foundations of electricty and magnetism, are expressed in vector calculus, if you want to really get to basics. Bob
  4. BobK

    Maxitronix Electronics Lab 300 in 1, BROKE ON THE FIRST DAY??

    Maybe a fuse? Bob
  5. BobK

    sort of an odd situation

    I would reccomend "The Art of Electonics" by Horowitz and Hill. It gives you the basic theory you need to understand how electronic circuits work without drowning you in math, but also without avoiding it where it is necessary. Bob
  6. BobK

    sort of an odd situation

    It is unlikely that you actaully need to do calculus, i.e. solve differential equations in order to be an electronic or radio hobbyist. Yes, if you where to try to invent the Chebyshev filter and calculate it's poles and zeros, you would need to solve differential equations in complex space...
  7. BobK

    Transistor Basic Basics

    Perhaps it would be best if you gave an example of a calaculation that you cannot manage, then we could walk you through it. Or an example of where you are seeing results that do not match your calculations, perhaps we could point out what you missed or where your expectations are wrong. Bob
  8. BobK

    IR Remote Control Help

    There is some kind of miscommunication going on here. There is no connection between the transmitter and receiver execpt via the IR light. If the receiver is seeing the transmitter, then it will output a zero (it is active low) and if it is not it will output a 1. To use the receiver...
  9. BobK

    CMOS gate not working?

    Yep, no connection is not the same as 0V. Bob
  10. BobK

    CMOS gate not working?

    You cannot just leave the inputs unconnected, they must be connected to either a low or high signal at all times. Try connecting the two inputs to ground and see if the LED goes off. Bob
  11. BobK

    Looking for an RC Transmitter & Receiver

    Sorry, I did not see the links. These modules are intended to transmit serial data, and they list the min baud rate at 50. So it is not possible to just send a steady state. The output will be high when there is no data coming in, so that is probably what you are seeing. Try putting an...
  12. BobK

    USB charger.

    What are you planning on charging with this? If it is a cell phone, you will exhaust the 9V without fully charging the phone. Perhaps it is OK for an MP3 player. Bob
  13. BobK

    IR Remote Control Help

    Define "this". Are you talking about the receiver I sent you a pointer to, or your photodiode and filters? Bob
  14. BobK

    IR Remote Control Help

    Well, for less than 1$ US you can get the entire receiver in a 3 pin package (Power, gnd, signal out). But these work at higher frequencies, usually around 38KHz, which is what you TV remote uses. http://www.mouser.com/catalog/catalogUSD/644/192.pdf
  15. BobK

    Powering a 12v computer fan

    What, you don't have a box of about 50 of them you have accumulated over time? :) Bob
  16. BobK

    multi direction dc motor

    I thought I said that :) Bob
  17. BobK

    Looking for an RC Transmitter & Receiver

    Can you give us a link to the transmitter and receiver you got? Bob
  18. BobK

    multi direction dc motor

    In addition to what duke37 said, you cannot use an NPN transistor for the high-side switches in your bridge. You need a PNP transitor for these. Assuming the uC is putting out 5V, the base of the NPN high-side driver is going to be at 5V when you turn it on, which means the emitter can rise...
  19. BobK

    New circuit for a beginner

    This would be easy with a microcontroller. Not so easy otherwise. Bob
  20. BobK

    PWM channel to control LED's

    The circuit is fine. But it is a very inefficient way to drive the LEDs from 12V. If you were to put 3 LEDs in series, it would draw the same current as one LED is drawing now. In fact, if the current arrangement is drawing 80ma that is 10 ma per LED. If you made 3 strings of 3, 3 and 2...
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