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  1. F

    Just learning and confused what this resistor does

    If you put the LDR in place of the resistor then it could turn the transistor on and off "on it's own". The problem is that it would turn it on when the light is on and turn it off when there is no light.
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    Advice needed for 6V to 12V conversion, Ride on kids car

    I know this is an old thread, but I want to add a warning for anyone doing this upgrade. I upgraded by grandson's riding car from 6v to 12v simply by changing the battery. It worked great, The car was faster but not dangerously so. But one time when leaning backward at startup the car did a...
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    How Is This RC Circuit Dropping Voltage

    It's been about 50 years since I learned about calculating total impedance(Z) so I might be wrong, but I'm pretty sure you cannot simply add resistance and capacitive reactance. Rather you must use vector summation that accounts for the lead factor in capacitors (or lag factors in inductors). By...
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    Current measurement circuit , Shunt resistor value Selection

    The 100k resistor is a compromise. A higher value resistor increase the voltage the microcontroller sees, but decreases the current flow. Vice-versa for lower value resistors. The 100k resistor introduces anywhere from 2% to 8% reduction in current flow depending on the actual value of R0. You...
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    Caller ID stumper

    Wild stab in the dark...disconnect all other phones, answering machines, etc. from the line and see if CID works on one phone. If possible, connect that phone as close as possible to where the phone line enters the house and disconnect the internal house wiring as well.
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    Is it possible to use two LED with a 3-pin non-latching Hall effect sensor?

    Haraid, Thanks for fleshing out my idea. The forward voltage requirement of more than 1 volt for most LEDs could also be a problem. The original post says that one LED could be driven, probably using the sink capability of the sensor. So maybe only one transistor is necessary to drive the...
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    Square wave to DC level

    Relative to my last post where I said the only components required were those to construct a simple voltage divider because the PIC was fast enough to detect the square wave directly with some fairly simple software. Overnight I realized that you probably should put a diode in series with my...
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    Is it possible to use two LED with a 3-pin non-latching Hall effect sensor?

    At a glance it looks the the sensor idles at 1v with no magnetic field and varys roughly _+ .9v according to magnet polarity. By connecting two LEDs, each one attached between a 1v reference voltage and Vout but with opposite led polarity the LEDs should light independently according to the...
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    Square wave to DC level

    I don't know much about the PIC, but I don't think you need an external "edge trigger" of any kind. Perhaps you are referring to the PIC's interrupt processing capability, which probably operates on it's own internal edge trigger. However interrupt processing should not be necessary unless the...
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    POE 48vdc to 24-26 vdc

    As others have implied the LM317 will not work because it is a linear device and cannot provide more current than available at it's input. Think of it as an automatically adjusting resistor. This might work for you..I would put it on the far, Nano Beam end, of the wire...
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    Square wave to DC level

    I am confused, if all you want to do is detect the presence or absence of a 4 khz square wave signal the PIC can do that without any additional circuitry. Except maybe for a simple needed resistor voltage divider to adjust voltage levels to that acceptable by the PIC. All you have to do is...
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    TDA7297 cascade channels?

    I should have mentioned that the radio is AM/FM so maybe the bass boost circuit should be left intact. Thank you
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    TDA7297 cascade channels?

    The module has a gain control that simultaneously adjusts both channels. So by adjusting the gain hopefully that will solve the "too much gain" problem. Anyway, I just checked the module again and it is dead. Somehow the unregulated 17v level of the 12V wall wart that I substituted must have...
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    TDA7297 cascade channels?

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    TDA7297 cascade channels?

    That sounds workable, I may give it a try if my module is still working (see my other post). Good tip about zero output at the center tap. Thank you.
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    TDA7297 cascade channels?

    Wow, what great feedback..Very helpful. Thanks everyone. Let me try answer all the questions. 1. I took the output from the car radio volume control center tap. It's about 50mv P-P. 2. The speaker was 8 ohms, although according to the radio schematic the required speaker is 10 ohms (1972 olds)...
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    TDA7297 cascade channels?

    I have an inexpensive Chinese TDA7297 module that I want to use to replace the audio output stage of an old car radio. The problem is that the module does not have enough gain. The radio is mono and the module is stereo so I was wondering if I could cascade the channels to get more gain...
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    Square wave to DC level

    I'm not sure that I follow your question. Why do you apparently want to to convert a square wave to some kind of analog signal? What does the square wave signal represent?
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    1970 Delco Radio Repair - audio distorted

    Right now the gain of the 1st stage seems to be about 1/2 what it was when I began troubleshooting. I must have done something stupid to cause this but nothing obvious is evident. It's a pretty simple circuit so I am disappointed that I haven't figured it out. Although if I do fix my apparent...
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    1970 Delco Radio Repair - audio distorted

    Here is the audio and PS section of the schematic that seems pretty close to my radio. I think it will answer many of your questions. BTW, it's not stereo and no tape player. The 5.6 ohm resistor in my radio is R59 (2.7ohm) on the schematic. Another difference is that my radio has the...
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