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  1. Externet

    12V DC motor with 12V battery getting hot

    Yes, it is safe. Several reasons for heating... - The motor is bad. - The motor is not 12V, perhaps it is for lower voltage. - The motor is turning a load greater than it is capable of driving. - The duty cycle for the motor is exceeded.
  2. Externet

    Wiring 100 speakers together, help!

    Hi Sara. 100+ speakers, wiring them, mounting them... and cheap... hmmm Unsure of your intentions with that many speakers, if it is for an artistic wall or similar. Just trying to make sure you know that these things exist : ----> http://www.feonic.com/flat-panel-speakers ---->...
  3. Externet

    B&K Precision better than Tektronix ? (Oscilloscopes)

    Personally, I would buy anything but not a Tektronix. The thing I have done the most with Tektronix is repairing them. Their power supplies stink, designed to fail. Am happy with a very humble Hitachi. Sold all my 3 Tektronix.
  4. Externet

    Wiring 100 speakers together, help!

    Yes, 100 speakers or more can be connected together. Just wire them in a series parallel configuration array (matrix) to bring the total impedance as near as possible to the amplifier output impedance. Like a series of ten paralleled to 9 series of ten. oooooooooo oooooooooo oooooooooo...
  5. Externet

    Inject sound to a phone landline

    ..."you forgot that phone line is 42 v to 100 V"... No. I did not forget. A telco line pair will have near 50 VDC when on-hook; about 8VDC when off-hook; and about 86V AC at 20 Hz when ringing; and around -9dBm (0.25VRMS) audio during talk; and the DC load presented by the telephone apparatus...
  6. Externet

    Inject sound to a phone landline

    To inject or extract audio to/from a telephone line, use any 8 ohms to 1Kohms audio output transformer, can be obtained from RadioShack or pulled from an old transistor radio.. The 8ohm winding connected in series to only one of the telco pair wires. The 1Kohm winding for audio source. ---->...
  7. Externet

    Driving a led from high-voltage source

    High voltage presence monitoring is not done with a LED, but with a neon bulb. And there are sub-miniature ones as used in photo cameras flash circuits. A proper resistor in the MΩs range should provide brilliance in the high voltage range. And a LED does not 'take 20mA' as stated. Can be...
  8. Externet

    How to make a circuit to test ringers in rotary telephones ?

    I have done it maaany times, by connecting the telephone to 110VAC 60Hz with a 10K resistor in series to test ringers.. The telephone must be on hook or you will fry it.
  9. Externet

    Solar Garden LED lights upgrade.

    My garden lights had these 200mAh crappy chinese cells: ----> http://image.made-in-china.com/2f0j00rCETWbhybszj/NiCd-Rechargeable-Battery-AA-200mAh-1-2V.jpg Replaced with: ---->...
  10. Externet

    wind turbine to battery

    Hello. I would use a diode to prevent the battery from 'backflowing' into the generator. When the voltage generated overcomes the battery voltage + diode drop, will charge it. Overvoltage generation at high speeds is another subject, right ? Would take some regulator circuit to limit or chop...
  11. Externet

    alert about distance between 2 objects

    :p ----> https://duckduckgo.com/?q=child+distance+alarm ----> http://www.specialtyalarms.com/site/1313932/product/30-210
  12. Externet

    Momentary Buzzer

    In parallel to the remote control transmitter power wires, a buzzer in series to a capacitor can be implemented. The buzzer can be as simple as a relay. (+)------------||---------------ΩΩΩΩΩ-------------C-----/ --------NC------------(-) ΩΩΩΩΩ = relay coil C = common contact NC = normally closed...
  13. Externet

    Building wiring circuit keeps tripping breaker.

    Disconnect/disable any item that was in use at the moment of breaker tripping; preferable the suspect new hand dryer to confirm if the behavior persists or not. If power disruption persists, That dryer circuit can be assumed healthy. Move the wiring in the breaker box to another equal-rating...
  14. Externet

    Can you identify this 14-pin IC in tone detector circuit from the schematic?

    Hi. Sorry, but changing the title may not bring much good in my opinion. Because may mislead. If the IC was a dual tone detector for sure, perhaps I would have found it. I wish it was. Hope for your clues. The exact description is, It is an adjustable dual tone detector AFSK circuit; but not...
  15. Externet

    Can you identify this 14-pin IC in tone detector circuit from the schematic?

    Thanks KrisBlue. Take a NervoCalm and ----> http://s588.photobucket.com/user/Innernet/media/DSCF0035.jpg.html?sort=6&o=44 The apparent 'chaining' of passive components (feedbacks, tuning, gain, ...) came to be like that just because coincided with a compact layout in the connections. Audio...
  16. Externet

    Sealed Lead Acid Batteries

    If we plug the main unit back in will the backup battery charge on its own? ---->It should. There has to be a trickle charger/maintainer circuit built-in. Allow several hours. A lead-acid that stays discharged over 24 hours will never recover its full capability, but may still work somewhat...
  17. Externet

    Looking for a consumer integrated circuit...

    Once upon a time, a plain old stereo receiver had a tuning 'aid' made of three LEDs in the shape of |> 0 <| The red triangular outer LEDs showed off tune. The green central LED showed when a radio station was properly tuned. The LEDs were driven by a simple consumer IC. What ICs that you...
  18. Externet

    Can you identify this 14-pin IC in tone detector circuit from the schematic?

    Hi am looking for a similar functionality of a CD4046 IC but in 14 pins. Any family as CAxxx, CDxxx, MCxxx or else. Do you have suggestions ? This is a very, very difficult question but gave up on other means to locate/search such probable chip. It is for a proven good working...
  19. Externet

    making a big magnetic field

    You will not satisfy size, weight nor wallet : ----> http://military.wikia.com/wiki/Directed-energy_weapon
  20. Externet

    How to switch off an audio signal

    A couple of things... -May be better to short-circuit to ground the microphone while the speaker is active instead of leaving it floating with the switch and get hum. -If you built the robot, there could be a software solution by inserting a program line to ground/ignore the microphone input...
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