simulating water conductance in multisim

[sunnyimran]

suggestions would be great help indeed.

for capacitive probes I have another idea shortly:

since I need to measure levels at cetain discrete measures only, I can create a capacitive probe in this manner

in a pvc pipe, I can connect many capactiors in series with each other. the connectting junction between any two capacitors will be exposing out of pipe.

when water is empty, all capactiros in series will form a circuit. when water rises, each exposed junction will come under water, sort of short capacitors with water presence and that will change the oscillating frequency. 

for my original idea on which I boiled down everything to a schmitt inverter buffer. 

now I have two choices from CMOS family

74hc14 or cd cd40106B 

I have to analyse specs for both.

Since my need to sense the levels is immediate. controlling motor and alarming may have time ( with microcontroller) so I decided to run one or two LED bars with this schmitt inverter and also to run 3 digits of 7-seg display to show levels at a resolution of 10%.

That's  all I need to implement at the moment and install as soon as possible. if you can kindly suggest me the logic series to use form CMOS for all devices in this scenario that can reduce a lot of time and effort for me.

If all can be done with a 5V supply constraints it would be good. otherwise I should use devices with higher supply rating.

what I am worrying is that at inputs of the inverter gate, approx 10m of cat5 with capacitive/resistive effects may false the logic. so I will try to get bi-polar oscillated signals as inputs. currently idealizing on this, will share later.

kindly suggest the series for me. 

74HC or cd4.... or what 

thanks again for all the support

[sunnyimran]

First I will design a plain circuit and test with 10m cat5, if everything is fine then no need osciallting signals

[johnsold]

The 74HC14 and CD40106 are essentially equivalent except for the power supply range.  At 5 V they are interchangeable.

For your capacitive probe are you using the water conductivity to connect the "junctions" between capacitors? Or are you using capacitors with the plates exposed to the water so that the conductivity "shorts" out any capacitor with its plates covered by the water?

Whether the 10 m of CAT5 cable will be significant depends on what your minimum and maximum capacitance and resistance will be at the sensor and what frequencies you will be using.  I cannot make any recommendations without some numbers.

Lynn

[sunnyimran]

---

johnsold wrote:

For your capacitive probe are you using the water conductivity to connect the "junctions" between capacitors? Or are you using capacitors with the plates exposed to the water so that the conductivity "shorts" out any capacitor with its plates covered by the water?

Lynn

the idea for capactive probe is to use fixed value capacitors in a series string such that each junction ( the wire connecting two capacitors in series) will be exposed to water, the string embed in pvc pipe. 

got a bit busy now a days, so working slowly. 

got the difference between 74hc... and cd... , noise margin is almost similar.

The idea to embedd sensing gates chips inside the sensing probe and bring gate output towards other circuitary via long cat5 wire requires the supply rail to reach into the sensing probe. in this case I have to bring VDD ( +5V) into the sensing probe from the main circuit via the cat5 cable which I will also use as gates output.

Now to feed supply to logic gates embedded in my sensing probe:

Q. so should I supply higher DC voltage at circtuit end and after the long cat 5 cable, I use a regulator to supply +5V dc to logic gates embedded in the probe? I mean regulator also embedd within sensing probe.

Q. if use +5v DC, will it degrade down to something lower after this long cat5 cable?

Q. or should I supply AC voltages then convert it to DC rails inside probe?

which idea is more safe and better.

thanks for all the support

[johnsold]

The anwer to your questions depends largely on how much current will be drawn by the circuits at the probe. An oscillator draws more current than ordinalry logic circuits.  According to Wikipedia the DC loop resistance for CAT 5 cable is < 0.2 ohm/meter. So you should have about 2 ohms at 10 m. Unless you are drawing more than 100 mA, the voltage drop should not be a problem.

Keep it simple. Just put the sensing circuitry at the probe and keep everything else back at the host site.

Lynn

[Kizznyc]

HELP!!!!

Design, simulate in multisim, and implement in breadboard, a motor controller for a water pump

to pump water from a well to fill an over-head tank. Use digital logic ICs from 74 series or 4000

series families. A suitable DC electromechanical relay can be used to drive the motor.

The following inputs and outputs should be incorporated:

 Start Push button

 Stop Push Button

 Low-level float switch

 High-level float switch

 Pump starving sensor/switch

 Over-load sensor/switch

 Pump Not running indicator (green)

 Pump Running indicator (Red)

 Low-level Indicator (Red)

 Medium level indicator (White)

 High-level indicator (Green)

 Over-load trip indicator (Yellow)

 Pump starving indicator (Blue)

[Kizznyc]

HELP!!!

Design, simulate in multisim, and implement in breadboard, a motor controller for a water pump

to pump water from a well to fill an over-head tank. Use digital logic ICs from 74 series or 4000

series families. A suitable DC electromechanical relay can be used to drive the motor.

The following inputs and outputs should be incorporated:

 Start Push button

 Stop Push Button

 Low-level float switch

 High-level float switch

 Pump starving sensor/switch

 Over-load sensor/switch

 Pump Not running indicator (green)

 Pump Running indicator (Red)

 Low-level Indicator (Red)

 Medium level indicator (White)

 High-level indicator (Green)

 Over-load trip indicator (Yellow)

 Pump starving indicator (Blue)

[sunnyimran]

I replied you in your private message