ELECTRONIC WATER LEVEL INDICATOR & CONTROLLER With LM3914

Thread Starter

hhhunzai

Joined Nov 14, 2011
72
Dear sir,
please tell me how may I post, insert or upload pictures on this site so that i will be able to Insert pictures.
 

bertus

Joined Apr 5, 2008
21,314
Hello,

There is this in the FAQ:

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Bertus
 

T.Jackson

Joined Nov 22, 2011
328
You probably should refrain from using the word "sir" so often. I tend to reserve it for times of respect. Like, when you get pulled over by the Police they may let you off with a warning for drink driving if you show a lot of respect. Call the Police "sir", and they might hand you a get out of jail card.

Is your name Bob Barnes by any chance? You sound like him a bit.
 

KMoffett

Joined Dec 19, 2007
2,918
Sorry hhhunzai, I don't think those are going to be a of immediate help. They are out of focus, many wires are masking component locations, and it would take a good day or more to try and reverse engineer the pref board back to a schematic to check for errors.

How about we start with basic troubleshooting. Do you have a voltmeter?

Ken
 

Thread Starter

hhhunzai

Joined Nov 14, 2011
72
Yes sir I have a digital voltmeter. and it is possible for me to troubleshoot the circuit.
Beside this I am thinking, why don,t I make a circuit on AutoCAD, of the fabricated circuit board. Will this be an easier way?
 

KMoffett

Joined Dec 19, 2007
2,918
I was just thinking of troubleshooting what you have. Recall, in my schematic posting I said "It's not bench tested (or simulated)"

Apply DC power (12V).
Connect something to the SSR output to monitor it's operation.
Connect the probes, but not in water.
Are any of the LEDs lighted?
Is the SSR switched on or off?
Does pushing the switches change the state of the SSR?
Can you measure an AC voltage between the "Drive" electrode and ground?

Ken
 

Thread Starter

hhhunzai

Joined Nov 14, 2011
72
1. I have applied 12V DC.
2. Connected voltmeter buzzer on the output of SSR but it is not ringing.
3. Connected probes with a wire jumper, Previously I had done this by dipping probe in water as well as with a wire jumper, but the LEDs are not tilting.
4. There is not any response from SSR, but when I checked it before three days it was responding like a diode. It was allowing flow on one side but when I connected multimeter leads it was net responding. this flow was occurring when I supply the power to circuit, after removing power it was allowing only for four to six second then its stopped.
5. Pushing the switches no any response is coming.
6.Voltage between drive electrode and ground is 6.35V AC and voltage between drive and all probes is 6.07.
 

KMoffett

Joined Dec 19, 2007
2,918
....
6.Voltage between drive electrode and ground is 6.35V AC and voltage between drive and all probes is 6.07.
Good! We now know that the power connects to U1 are correct and that the oscillator is working.
Now, connect a jumper between the Drive electrode and the High sense electrode. Does the LED light? Do this for each sense electrode.

Ken
 

Thread Starter

hhhunzai

Joined Nov 14, 2011
72
I already have mentioned this, I had checked by shorting the drive with each sensor. But the LEDs are not lighting.
 

KMoffett

Joined Dec 19, 2007
2,918
Bertus,

Are you referring to my schematic or the OP's photos? C15/C16/C17 in my schematic are for IC bypass. I count seventeen capacitors in the OP's photos.

Ken
 

bertus

Joined Apr 5, 2008
21,314
Hello,

Taking a closer look at the photos, they seem to be there, although the connections are quite long.
Also an larger capacitor (10 - 100 uF with a 0.1 uf parallel) at the power entrance would make the circuit more stable.

Bertus
 

KMoffett

Joined Dec 19, 2007
2,918
Agree with bypass layout issues. The addition of bulk supply capacitors will depend a lot on the power supply used. But at this point, I would prefer to deal with which sections are working and which aren't.

Ken
 

Thread Starter

hhhunzai

Joined Nov 14, 2011
72
The inputs of NAND gates are as follow:
U1B=5.75VDC
U1C=5.80VDC
U1D=5.81VDC
U1B=5.81VDC
U1C=5.81VDC
When these inputs are coming to the NAND, the output remains the same (11.97VDC).
It is obviously not output, but the voltage coming through LEDs and resistors connected to 12 v supply in series.
I measured these voltages on each sensor one by one.
 

Thread Starter

hhhunzai

Joined Nov 14, 2011
72
Yes you are right, I have read the data sheet. please tell me what may I do to increase T+ for inputs.
Is there any solution available for this?
 
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KMoffett

Joined Dec 19, 2007
2,918
Big OOPS!
Change R1-R5 to 100K or higher...maybe 470K.
When I created the schematic I copy/pasted the resistors, and forgot to change those values. That should bring the voltage up. I'll post the corrected schematic here later.

Have to go now.

Ken
 

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