ELECTRONIC WATER LEVEL INDICATOR & CONTROLLER With LM3914

hhhunzai

Joined Nov 14, 2011
72
Ok I am going to change these resistors.
If I will change it to 470k is it ok?

KMoffett

Joined Dec 19, 2007
2,918
Should be OK, but I would change just one to start, to see if it gets the result we want.

Ken

Last edited:

hhhunzai

Joined Nov 14, 2011
72
The circuit is going to working I think, First LED is lighting, but the remaining are still off.
I have used 110K resistance with first sensor.
Previously I had used 470K (R5 in schematic), with last LED but it was not lighting.
Then I changed it to 100k.
please guide me what is the root cause of others even I have used 110 with all except with R5, I have connected it with the 100K resistance.

Now the DC voltage on I/P5&6 of U1 are 10.22=out0.50, I/P on U1 8&9 10.27= out 10.37, I/P on U1 12&13 10.27= out 10.37, I/P on U2 5&6 10.27= out 10.37, I/P on U2 8&9 10.19= out 10.37,

HHH

Last edited:

KMoffett

Joined Dec 19, 2007
2,918
What values do you have R1, R2, R3, R4 and R5?
When you test them do you connect the drive electrode to each of the sense electrodes, one at a time?
What voltage do you get at each of the gate inputs when you do this?

Ken

hhhunzai

Joined Nov 14, 2011
72
I had connected one sensor at a time and then sensor 1 and 2 both step by step at a time,
but only LED one was lighting
As I said before DC voltages on gate inputs are,
U1 5&6 10.22V =out0.50V
U1 8&9 10.27V = out 10.37V
U1 12&13 10.27V = out 10.37V
U2 5&6 10.27V = out 10.37V
U2 8&9 10.19V = out 10.37V

Resistances are,
R1 = 110K
R2 = 110K
R3 = 110K
R4 = 110K
R5 = 100K

KMoffett

Joined Dec 19, 2007
2,918
Do the four gates that show high (10.37V) output with a high (~10V) input, go low with a low input?

Ken

hhhunzai

Joined Nov 14, 2011
72
Should I decrease the resistance for the remaining? Or Should I change all with the same resistance?
HHH

KMoffett

Joined Dec 19, 2007
2,918
Leave all the resistors at ~100K. If the gate inputs are changing from ~0.0V to ~10V and the gate outputs are not changing then:
1. The chips are damaged or
2. You have wiring errors.

Ken

hhhunzai

Joined Nov 14, 2011
72
Have you tested it by yourself Mr. Ken, because I am a Little confused about it, why it is not working.
Please tell me if you have tested it by yourself.
And is there any method of testing these ICs?

KMoffett

Joined Dec 19, 2007
2,918
I have used versions of the inputs...4093 drive-oscillator, voltage doublers, and 4093 detector-gates..for water level detection in the past. As I said in my original post, I have not bench tested or simulated the whole circuit.

Since you have one level detector that is working, it means that the design is working, and part of your layout and part of one IC is good.

Do this directly to the IC pins, not to wires or component leads going to the pins:

1. Check all the IC's for +12V on pins #14 (negative meter probe to ground), and for -12V on pins #7 (negative meter probe to +12)

If OK:

2. Apply +12V through a 10K resistor the each of the detector-gate's input pins.

Do the LEDs light?

Ken

hhhunzai

Joined Nov 14, 2011
72
Your point no. 2 is I think -12V not + 12volts?
Your first point is right and all connections for all three ICs are right and they are connected. #14 to +12 and # 7 to -12 volt.
But u are right the only LED which connected to input No. 5 & 6 of U1 is working and the others are still not lighting.
Please tell me a method of testing only IC.?

Last edited:

KMoffett

Joined Dec 19, 2007
2,918
Your point no. 2 is I think -12V not + 12volts.
If wired correctly, there would be ~0.0v at the gates' inputs with no water detected. If water is detected (or there is a jumper to the drive electrode), there should be ~10V at the gates' inputs. What I was suggesting is a way (+12V through a 10K resistor) to bypass the input's voltage-doublers and try to directly activate the gates. But you did say, you were getting ~+10V on the non-functioning gate's inputs. Was that measured directly on the gates' IC pins, or on other component leads that would be connected to the pins?

Ken

hhhunzai

Joined Nov 14, 2011
72
I had measured those voltages directly from inputs.

KMoffett

Joined Dec 19, 2007
2,918
Then it sounds like the LEDs on the outputs are not connected correctly or parts of the chips are bad.
Visually assure that the connections between the +12V buss, LEDs, resistors, and gate outputs are correct. To verify the polarity of the LEDs, connect a 1K resistor between ground and the bottom lead of each LED (as shown in the photo of board bottom). This should light the LED even if the associated gate is defective.

Ken

hhhunzai

Joined Nov 14, 2011
72
Please tell me the Pin configuration of HTC semiconductors LM7812.

hhhunzai

Joined Nov 14, 2011
72
If this power supply is going to work or Not, please tell me about it.?
What more improvements can be done with this PSU?

Part Total Qty. Description
C1 1 2200uF, 35V, Electrolytic Capacitor
C2, C4 2 0.1uF Ceramic Disc Capacitor
C3 1 10uF 35V Electrolytic Capacitor
D1, D2 2 1N4007 Silicon Diode
BR1 1 2A 30V Bridge Rectifier
U1 1 Regulator LM7812C-12V
T1 1 Transformer 12V, 1.5A
S1 1 SPST 2 Amp Switch
F1 1 2A 250V Fuse and Holder
MISC 1 Heat sinks For U1, Line Cord, Case, and Wire

Attachments

• 49.6 KB Views: 16
Last edited:

KMoffett

Joined Dec 19, 2007
2,918
The power supply is a valid, general design. You would need to state input (VAC) and output (V and I) specifications to get component values.

Where are you on the getting rest of the circuit operational?

Ken

hhhunzai

Joined Nov 14, 2011
72
Thanks, well this circuit is actually being designed for that circuit, which we have discussed allot, I was thinking of the power supply problem therefore decided to make this circuit, so let's see what happens with the other circuit after this PSU.

KMoffett

Joined Dec 19, 2007
2,918
What were you using for a 12V power supply?

Ken