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  1. Hero999

    my transistor gets hot, line follower/dark sensor

    Posting a schematic would make it easier for us to help you. You obviously need to use a more powerful transistor and/or add a heat sink to keep it cool. Another option could be replacing the Darlington pair with a MOSFET or connect the collector of one of the driver transistor to +V, via a...
  2. Hero999

    How to make a regulated power supply with different dc output?

    Why not use the LM317 and put the the voltage selector switch on the potential divider? A Google image search returns a similar circuit to what you need on the third hit. It's easy to modify it to give the voltages you need. You'll need a higher voltage transformer than 12V to reliably get 12V...
  3. Hero999

    How to make a regulated power supply with different dc output?

    Try the LM317, a transformer, ectifier and filter capacitor.
  4. Hero999

    LE33CZ linear regulator

    http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000545.pdf
  5. Hero999

    Trying to build simply 3bulb LED light powered by single AA battery, with switch

    LED stands for light emitting diode and is not a bulb but a semiconductor chip which produces light when an electric current is passed through it. The voltage across the diode is dependant what the chip is made of and the current flowing through it. You need to limit the current which can be...
  6. Hero999

    Trying to build simply 3bulb LED light powered by single AA battery, with switch

    A "Joule Thief" circuit can be used to power white LEDs from a single 1.5V battery. Mercury switches are banned in Europe. I don't know about the US. Fortunately, non-mercury tilt switchs are available.
  7. Hero999

    Charging circuit 4 AAA NiMh

    You're wrong, whether the resistor is in series with both the capacitor and battery or just the battery will make little difference to the charging time.
  8. Hero999

    Charging circuit 4 AAA NiMh

    The resistor is in series with the batteries. A capacitor is not necessary because the battery doesn't care about the ripple current. I agree, increase the resistor to 1k to 2k to limit the current to something more sensible.
  9. Hero999

    ignition device for a miners lamp

    Yes but the battery would need to be larger to get the same battery life because it would need to store more energy to make up for what s lost in the converter. 25Ah sounds much larger than necessary. Have you simply tried connecting three AA NiMH cells in series to give 3.6V to 4.5V? If that...
  10. Hero999

    Charging circuit 4 AAA NiMh

    The battery voltage is not the problem. The main issue is the charge current is too high.
  11. Hero999

    ignition device for a miners lamp

    Ah is a unit of charge, normally used with reference to batteries, not current. It sounds like you need a 25Ah 4V lead acid battery. It will be very heavy though, 3.4kg (7 1/2lb) according to the data sheets I could find for batteries of this size. 4V is not a common voltage though. You may...
  12. Hero999

    rectifier snubber with RC

    Please post the schematic. It' s difficult to help without seeing exactly what you're doing.
  13. Hero999

    cables for digital signals

    It depends on the signals i.e. whether they're single ended, differential and the line drivers/amplifiers used. If the cable's impedance is matched the distance is limited by the: standing wave ratio, acceptable delay, signal attenuation and noise.
  14. Hero999

    Help needed to make 555 timer circuit throw relay.

    A 555 timer can drive a relay as long as the coil current is below 200mA. A diode needs to be connected in reverse parallel with the relay coil to protect the 555 timer from the high voltage pulse generated when the relay is switched off.
  15. Hero999

    I NEED A 2 Khz sine generator !

    What PDF? You haven't posted it. A simple phase shift or wein bridge oscillator can be used as sine wave generator or a squarewave can be filtered to make a sign. Velleman do a kit (MK105) which gives a fixed 1kHz but can easily be modified to produce 2kHz.
  16. Hero999

    Relay - Pin Numbering ?

    Pins 5 & 6 are connected together inside the relay, as per the pin out you've posted. You don't need a voltage regulator. The relay has a coil resistance of 162R so simple 1k 1W connected in series with the relay will do. http://teachmetomake.files.wordpress.com/2011/02/relay-g5v1.pdf
  17. Hero999

    Capacitors

    Perhaps you've not received any replies because your question is so vague? How are we supposed to know what sort of capacitor is uitable for your project when we don't know what it is?
  18. Hero999

    Relay - Pin Numbering ?

    That should work but you've draw it with the red and green LED the wrong way round. The convention is to show the contacts in the de-energised state. Why not skip the voltage regulator and buy a relay which can work off 36V in the first place? Alternatively, you could use a 24V relay and put a...
  19. Hero999

    DC converter 12V to 24V with dual outputs (+24V and -24V) w.r.t. input GND

    To get a +24V supply with respect to 0V, you need a 12V to 24V DC-DC converter. To get -24V with respect to 0V, you need a 12V to 24V converter with an isolated output. Digikey sell plenty of PSUs which meet your requirements...
  20. Hero999

    I want to promote my electronic site in a correct way. Help me.

    If you keep posting the same thing over and over, in multiple threads, people will see you as a spammer. If you appear to be trying to sell something (even if you're not) people may think you're a spammer. Parhap you should make a few posts introducing yourself and about other people's projects...
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