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    need help

    dintence01, We can try to help, but must start with some questions: Do you have a volt meter, or multi-meter of some sort? Do you have equipment for soldering? Do you think you will be able to work from a schematic diagram, or will you need more of a picture showing the wiring...
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    LM317 circuit

    Plague, I don't think Dave D.'s reply makes much sense. Perhaps he was driving at the time? The data sheet shows that this part may have three pins, but only two are used. Do take heed to the suggestions about laser diodes requiring a current source, not a voltage source. A series...
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    Logic gate input from comparator

    Matt, I think the way the 4060 works, is that as long as the reset pin is high, the oscillator is inhibited, and all the outputs are zero. When the reset pin goes low ( and stays low ) the oscillator starts, and the counter starts counting. Look at the logic diagram on the Motorola...
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    Logic gate input from comparator

    Matt, 30 minutes is really too long for an NE555 timer; the timing R and C must be too large, and you are at the mercy of capacitor leakage current. See Steve's article. I suggest you look at the CD4060 ( MC14060 ). It contains an oscillator, plus a 14 stage ripple counter. The...
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    Logic gate input from comparator

    Matt, The other forum members have offered good advice. If the delay time you need is on the order of a few seconds, the suggested NE555 would be a good bet. It should be able to provide your delay, while driving the relay directly. If you don't like using an NE555, you can...
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    USB current detection

    EventHorizon, You need to try your fan, and see what it does. Many "computer fans" use brushless motors, and have no mechanical commutator. The brushless motors have an electronic circuit to switch the DC power to the motor windings. Those fans are unlikely to work for you. You...
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    Pink Noise Generator

    Steve, Somewhere, there must be some published experimental data on how BE junction breakdown degrades transistors, but I have no idea where it might be found. My reference is the late Bob Pease, who mentioned this effect in his column more than once. As I recall, he said that the...
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    Pink Noise Generator

    Ioamobn, I think you had better wire up an actual transistor and resistor and see how much noise you get. It's pretty clear that your simulation is not accurately simulating the transistor used in your referenced design. This is sort-of an off the books application for the transistor...
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    lm317 set up

    conntaxman, I agree that your circuit still needs work, in order to function at all. But I'm curious about some of your key components, beyond the LM317 circuit. Can you tell us more about the solar panel, and about the batteries you plan to use? Are there data sheets for these online...
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    adjustable amplified BJT circuit..help

    ahndy05, Thanks for your reply. We still need some clairification. I will try to find your transistor later, but the "H1061C" P/N is not immediately familiar. Do you have a manufacturer for it, so I'll know where to look? A link to the transistor's data sheet is always a useful thing...
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    USB Device

    Drew, All of the data acquisition hardware vendors make digital output modules for USB. The one cited by Steve is an example. One of these modules would minimize the hardware work you would have to do. Take a look at the products offered by FTDI. They sell modules, adapter cables and...
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    adjustable amplified BJT circuit..help

    ahndy05, Can you provide some more information? What sort of transistor? What's the temperature? Where is the output voltage found? Are the 2.5V and 4.5V values not-to-exceed values, or are they values that must be reached within the adjustment range? Are you looking for some values to...
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    Unexpected signal in circuit.

    Matt I'm trying to understand your application and its requirements. I wonder if trying to troubleshoot the posted circuit isn't an attempt to solve the wrong problem… Would you be willing to share your actual purpose? We might be able to provide better help. Does your load tolerate...
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    8255A or Mc6821???

    burassu, I've use both of these devices in the distant past. Although both serve the same basic purpose, they are pretty different in detail. These are both rather ancient NMOS microcontroller peripheral ICs, providing digital I/O pins. Both run at Vdd = +5V, both have "TTL" level I/O...
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    Unexpected signal in circuit.

    Matt, A couple of suggestions: I'm not sure about why you are getting the 50 Hz signal in your circuit, but the circuit has other problems that would keep it from working correctly. You definitely need to corrrect the DC bias for the op-amp inputs, and then may need to address feedback...
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    What 220V AC plug is this?

    eldavid0000, I believe your "220 VAC" plug is called a "Universal Mate-N-Lok" connector. The original source was AMP, but there are other manufacturers, including MOLEX and MADE IN CHINA, I believe. There are several other series of "Mate-N-Lok" connectors, for instance the...
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