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  1. audioguru2

    Transmitter for students

    Nobody has the circuit for an FM transmitter that operates in kHz frequency. FM transmitters operate at between 88MHz and 108MHz unless you are in Japan where it is a little lower. Some radio amateurs operate narrowband FM at higher frequencies. Wireless microphones used by performers opaerate...
  2. audioguru2

    dancing leds with counter

    Just look at the schematics and the datasheet for the display driver IC. I stuck them together but I left the RESET pins for you to figure out what to do with them. You also need to figure out what the circuit will do when it counts one more than 99.
  3. audioguru2

    Turning a 7805 on/off with a Push to Make Switch

    You forgot to say how much is its load current. A 7805 voltage regulator IC has a max operating current of only 8mA. It regulates very well with a load current up to 1A but can supply up to 1.5A with a small drop in regulation. Most of them limit the current at 2.2A. The max current for a...
  4. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    There is no -VE supply in this project. The supply is +12V and 0V. Did you make the wrong circuit or my corrected one? I don't know why my corrected one was deleted. MODERATOR EDIT: THE VALUES FOR C AND R IN THE PROJECT ARE NOT INCORRECT VALUES. BOTH SETS OF C AND R WILL GIVE YOU 50HZ, AS WILL...
  5. audioguru2

    Connection problem

    I think this circuit will detect each zero crossing of the mains:
  6. audioguru2

    white led

    We purchase extruded aluminum heatsinks for power transistors. The heatsinks have many fins for a high surface area. They are rated in their amount of degrees C temperature rise per Watt of power dissipated in the transistor.
  7. audioguru2

    Turning a 7805 on/off with a Push to Make Switch

    OOPS. Yes, you are correct. It is a 2N4403 transistor. I have corrected the schematic.
  8. audioguru2

    Transformer question

    Kevin, A transformer has a max VA rating or a secondary max current rating. You forgot to tell us the rating of your transformer. It produces its rated output voltage if it has its rated input voltage and has its rated output current. It is made to produce a higher output voltage without a load...
  9. audioguru2

    Connection problem

    Why are there two extra diodes connected to the AC? You don't want to connect AC to ground or to the output of the regulator. Look on the datasheet for a 78xx regulator. It shows the two capacitors that are missing on your sketch. Whay aren't your lines straight??
  10. audioguru2

    LM317 Variable power supply

    R1 is supposed to be 120 ohms or less for an LM317. If its resistance is higher then its output voltage might rise when there is no load. If R1 is 100 ohms and the pot is 2.2k then at max setting the voltage will try to reach 28.75V but it can't, so the range of the pot will be reduced. There...
  11. audioguru2

    LM317 Variable power supply

    Look at the datasheet for the LM317: Its input voltage must be at least 2.5V or 3V higher than its output voltage or it fails to regulate and passes the input ripple to its output. The factory tests ripple rejection with its input 5V higher than its output voltage.
  12. audioguru2

    guitar fuzz effect

    Hi Jojo, Aren't you Josh from the other website forum? You didn't answer my reply there. Is this the fuzz effect circuit you are talking about?
  13. audioguru2

    Sony KV-LS21M80 21" CTV service Manual needed

    I entered the model number of my Sony TV in Google and got its sevice manual for free and forums about it where people are discussing exactly the same problem mine had.
  14. audioguru2

    SL100 & SK100 transistor

    They are very old transistors in a metal TO-39 case. The old datasheet I saw didn't even say which is NPN and which is PNP. For low power I would use 2N4401 and 2N4403 transistors instead. For higher power I would use TIP31 and TIP32 power transistors instead.
  15. audioguru2

    LM317 Variable power supply

    No. The datasheet for a 78xx fixed voltage regulator shows how to add a 2nd transistor for current limiting. The amount of ripple on the output depends on a few things: 1) Each LM317 is different. Some are excellent and some are not as good. Look at the range of ripple rejection spec's on the...
  16. audioguru2

    Turning a 7805 on/off with a Push to Make Switch

    Hi MPapps, 1) Your circuit doesn't need base-emitter resistors because the output from a Cmos inverter goes to the supply voltage. 2) Your circuit doesn't need the NPN transistor because Cmos inverters can operate fine from the 12V supply and can drive the PNP transistor. 3) The 2N3703...
  17. audioguru2

    TV Signal Amplifier ?

    The video detector in a TV is a diode like in an old AM radio. It doesn't respond to frequency changes produced by FM. It would be difficult to make a TV transmitter and TV receiver with the video FM modulated because the bandwidth is so wide.
  18. audioguru2

    LM317 Variable power supply

    You cannot connect two LM317 variable voltage regulators in parallel because each one will have a different output voltage and the one with the highest voltage will power the load and the other one will do nothing or it will be damaged. You can connect a low value resistor in series with the...
  19. audioguru2

    Transmitter for students

    You can adjust the values of the tuned circuit in an FM transmitter to operate at nearly any RF frequency you want. But you won't find an FM radio that will receive it. FM usually has a wide bandwidth so a high frequency is used. It would be difficult to frequency-modulate a low frequency carrier.
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    It is just a power supply that has voltage regulation and current regulation. Here is a simple block diagram. What is confusing you?
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