Is this a AC or DC Curcuit?

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Discussion in 'The Projects Forum' started by Seaker, Mar 30, 2013.

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  1. Mar 30, 2013 #1
    Seaker

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  2. Mar 30, 2013 #2
    Metalmann

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    DC.:confused:;):D
     
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  3. Mar 30, 2013 #3
    BillB3857

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    One big clue to it being DC is the + sign at the top of the capacitor.
     
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  4. Mar 31, 2013 #4
    WBahn

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    An even bigger cluse is that it says that the supply is +9V to +12V.
     
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  5. Mar 31, 2013 #5
    nerdegutta

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    What about the ULN2004 datasheet?
     
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  6. Mar 31, 2013 #6
    BillB3857

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    Looking that up would require excess effort. A lot easier to come here and ask.
     
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  7. Mar 31, 2013 #7
    nerdegutta

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    Oh yeah, I forgot that. Excuse my ignorance. :D
     
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  8. Mar 31, 2013 #8
    WBahn

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    Plus, the schematic is pretty explicit without looking it up.

    What I had to look it up for was to determine what would happen with the floating inputs since seeing a floating input to an input to an inverter sets off all kinds of red lights in my mind. For this part, of course, that's find because these aren't actually inverters and we aren't dealing with MOSFETs.

    I can't help how many people have spent countless hours wondering why their design isn't working because they expected the outputs to drive HI when the input was LO. I've certainly seen lots of people get completely stalled because they didn't put a pullup on a 339 output.
     
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  9. Apr 1, 2013 #9
    Seaker

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    Thank you for the replies.
    Regarding the 9V and 12V indicators many of these designs us AC voltage by using a transformer.
    My assumption was it was a DC circuit but I wanted to check this assumption out with the skilled people here. If I appear to be lazy that is not the case and I am sorry that some feel this way!
     
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  10. Apr 1, 2013 #10
    WBahn

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    But then they shouldn't say +9V or +12V. It's the '+' sign that is the giveaway.

    You're fine. The assumption is that you simply didn't know what the information on the paper means. We all start out that way. Some of the responses can seem a bit biting, but usually it is us feeding of each other and not something being directed at the OP. Usually. There are certainly exceptions. :D
     
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  11. Apr 2, 2013 #11
    stevemcd

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    Credits to all the posts in reply. Yes it is requiring a DC supply, I have done a lot of research on water level metering (for my own interest on measuring retention tank levels). One of my interests lies in understanding the effect of long term immersion in a semi-conductive fluid of polarised electrodes. Clearly, one pole will oxidise whilst the other reduces. Ipso facto, the use of an AC signal on the immersed transducers may be a more long term method.

    At present, I am looking into ways of measuriong water levels that will reduce or eliminate the possible effects of having immersed DC poles. There are intersting options that include non-intrusive means (think infra red reflectors, density relflective sensors and so on).

    However you proceed, please update when you have made progress.
     
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  12. Apr 2, 2013 #12
    WBahn

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    One way is to insert a long thin capacitor that uses water for the dielectric below the water line and air for the dielectric above the water line. Now you have a continuous level meter. Another way is to use resistance wire that changes resistivity when it gets warm/hot. You then run a current through it and the part that is in the water stays cool while the part in the air heats up.
     
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  13. Apr 2, 2013 #13
    Metalmann

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    How about using Stainless Steel?:confused:
     
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  14. Apr 2, 2013 #14
    BillB3857

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    What is the tank made of? If a plastic tank, conductive strips (foil) glued to the outside can form a capacitor with the liquid in the tank. The higher the level, the higher the capacitance. Measure the capacitance, measure the level. Commercial units are available for the recreational vehicle market that do exactly that.
     
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