Tank Level Monitor Circuit!!

Discussion in 'General Electronics Chat' started by Nara Shikamaru, Mar 10, 2008.

  1. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    Hey Everybody!!....i have a concern!!......i need to do a circuit that moniotors me the level of a fluid in a tank.....the thing is that i have the design....but i need to count 5 seconds everytime that the liquid gets to the next level......i mean......

    the tank is empty.....you start pouring water, when it gets to the first level it must activate a circuit that counts me 5 seconds....after that you continue pouring water, when you get to the next level it counts again 5 seconds!!!and so on to the 8th level.....how would you do that??.....what kind of circuit would you need there?......thanks a lot!!!....i´ll left you the schematic so you can see it!!.....
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    use a 555 timer ic connected as a monostable
     
  3. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    obviusly!!...i thought of a monostable!!...but how would you "reset" it automatically?....for the next levels?.....when it hits the first level it counts the 5 secs....then afeter that you pour more water to the second level....how do you count with the monostable the 5 secs again?....without reseting it yourself?
     
  4. saidin

    New Member

    Mar 10, 2008
    8
    0
    So when the water reaches the first sensor it triggers the monostable, the output of which goes high, turning off a valve. When the 5s monostable pulse ends and Vo goes low the valve allows water to flow again until the water level reaches the second sensor at which point the same thing happens again.... ? Is that the solution you are after?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Have you built the first part of your circuit as shown in your schematic?

    The 4066B has a fair amount of resistance depending upon Vdd (look at the datasheet).

    It looks like you're using 6v. At 5v Vdd, typical resistance for a switch is 270 Ohms; probably around 230 Ohms at 6v. This means you'll have 560 Ohms total limiting the current through your LED's; if they're a typical red LED with a Vf of 1.9, you'll only have about 7mA current through them - they won't be very bright.

    You might consider using a ULN2804 IC to sink the LED current. This IC contains eight Darlington pairs, can be purchased for under $1, and is very easy to use.

    As things stand right now, you don't have a good place to obtain a logic-level signal to drive a timer.
     
  6. Nara Shikamaru

    Thread Starter Active Member

    Nov 24, 2007
    92
    3
    Ok Sarge!!...ill look for it!!.....and saidin....thats is exactly what im looking for!!!.......its for eight levels!!.....exactly what you said!!
     
  7. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You dont need to reset it. It resets automatically. The only thing you have to to is to trigger it again and this will be done with your level sensors connected appropriatelly
     
  8. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    The UNL2804 has a 10.5K input series resistance, plus 2 diode drops to ground. So to pull an input high would require that the resistance between the input and +6V be less than 15K to turn-on the output. Since the OP said "fluid" I'm not sure the resistance between an input electrode and +6V electrode would be low enough to work. With the 4066, if you he dropped the 330 resistor, the output switch resistance (250Ω) would probably be enough to limit the current for the LED and not exceed the max package dissipation (700mW). Plus, the input current for turn-on is in the sub-µA level, so might turn-on even with a high resistance in the liquid.

    But I liked the 2804. :(

    Ken :)
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    8 levels.jpg
    Make sure your level sensors send out a negative pulse. Not a negative level, mind you - that would re-trigger the monostable falsely.

    Perhaps you could use a float with a Hall effect sensor passing by several magnets. Or a float with a stick that moves a flag through several optical sensors. Or micro-switches. Or you could induce a current in the fluid with an induction coil, rectify and filter a signal representing the reflected impedance, and run that into a window comparator. Or not.
     
  10. vel

    New Member

    Apr 4, 2008
    3
    0
    pls sent non contact type circuits(non contact of water)
     
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