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  1. duke37

    LED's to MUSIC in car stereo or amp Circuit PROBLEMS (BEGINER) please help......!!!!

    It looks to me that it should work. Have you got a voltmeter? There should be 12V across the E-C on the transistor with the leds unlit or about a volt with them lit. When the potentiometer is turned up the B-E voltage should rise to 0.6V and the leds should light up. Turn the pot down so...
  2. duke37

    How does a UPS inverter works?

    The 4047 contains an oscillator whose frequency is set by a resistor and capacitor ( F = 1/(4.4*R*C) There is an internal divide by two circiut and two outputs, the division makes an equal on/off times and the outputs are in antiphase, When one is high, the other is low so that either one or the...
  3. duke37

    Is this AC adapter close enough?

    A Nixie tube requires about 100V through a resistor to run so there is likely to be a transformer to suit, Perhaps this transforms from 9V to about 100V.
  4. duke37

    100MHz counter

    I have a 10Mhz frequency counter board based on a ICM7216A. I would like to count to a higher frequency than this and have looked at various decade counters, they do not go to 100Mhz. CD74LS90 42MHz SN7490A 42MHz 74HCT4060 67MHZ 74HC4017 ? 77MHz Are there any decade counters that go to...
  5. duke37

    Broken wire through rubber on solenoid controller (on mini digger)

    I posted here before but it seems to have dissapeared. I agree with poor mystic that if you cannot get a new cable, the old one can be repaired. It looks as if the cable goes through a rubber plug which could be taken out without damage. If the wires are plugged in to the unit, new connectors...
  6. duke37

    help in making fm transmitter??

    The coil looks to be about 4mm diameter, put a 4mm drill bit the wrong way round in a hand drill and wind 8 turns. You could get a more accurate estimate by scaling your photo, knowing the size of the transistor. There are equations giving inductance for a specific design (try Wikipedia) The...
  7. duke37

    how to manually clock a 74163 IC?

    You have the CLK input switched to 5V, is that correct? The inputs I have seen sit high and need to be pulled low. Look on the data sheets.
  8. duke37

    Alarm clock radio - Speaker POP!

    Some high power audio amplifiers use a relay to isolate the speaker until the amplifier output has settled down. You could perhaps fit a relay to do this job if there is room. A gently turned on MOSFET would do a similar job. The problem may be that an electrolytic capacitor in the radio supply...
  9. duke37

    TIP162 (Darlington NPN) Substitute.

    And the test circiut includes an external zener.
  10. duke37

    What are these?

    Why do you want another if the value is right?
  11. duke37

    Building a pH meter

    You are not measuring pH, you are measuring voltage. If the probe has a source resistance of 100M it is necessary to have an amplifier input resistance much above this to get a reasonable reading. Any standard voltage measuring device such as DMM or scope will have an input impedance of about 1M...
  12. duke37

    diode ?

    An alternative is to use three relays, each one connected to a solenoid feed. The contacts of the three relays should be connected in parallel. This uses the components as they are designed.
  13. duke37

    diode ?

    The answer is YES! 240V AC relays will operate on DC, in fact they will operate with a lower voltage. I do not know the actuation voltage of the relay you have. To actuate a 240V relay from one or more of your solenoid supplies, each feed should be fed through a diode (1N4007 etc) to a single...
  14. duke37

    Low battery shut off (and warning)

    I do not understand why your second zener is hotter than the first since they pass similar amount of current at a similar voltage. My calculation is that the dissipation is about 120mW which most zeners can manage comfortably. Do not put a resistor in series with the zener, this will upset the...
  15. duke37

    Building a pH meter

    I know nothing about pH probes but I looked up "glass electrode" on Wikipedia. The probes have a resistance between 50M and 500M so would be very difficult to measure. The probes are sensitive to storage and should never be allowed to dry out. I would think that the only way to check is to test...
  16. duke37

    Building a pH meter

    I used the english idiom since fet input op-amps can be sensitive to static electricity., I will try to use plain english in future. You say that it works as a follower or invertor, it should not invert but I presume that you mean that it works with positive or negative input and gives a...
  17. duke37

    Building a pH meter

    You need to locate the problem. 1. Short the input and check the output is within a few mV of ground. 2. Replace the short with a high value resistance (10M), has output changed? 3. Input a voltage from a single cell, does the output match? 4. Reverse input polarity, still OK? 5. Try probe...
  18. duke37

    amplifier and unwanted oscillations

    Are you sure that you are not picking up a radio signal, how about a medium wave radio station, fluorescent light, ultrasonic bath, induction heater etc.
  19. duke37

    amplifier and unwanted oscillations

    Oscillations occur when there is feedback in the amplifier system. This can happen by feedback in the chip or outside the chip. To reduce feedback in the chip, place a capacitor (10microF?) directly across the chip power supply. To stop external feedback, both capacitive and inductive, use...
  20. duke37

    Firing 3 LED's using two switches and 3 wires

    With luck, the diagram may help.
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