Question on the Plants Watering Watcher circuit

[ante1]

From the original circuit remain one resistor, one potentiometer two caps and a LED. I would call that a change.
Where is the finished circuit then? I sure there are some readers that are a bit confused not getting to see the hole picture (drawing).

Ante :

 

[audioguru2]

Here is my slightly modified schematic of this project:

View attachment 35376

 

[MP1]

Do we have ANY projects that work properly? (2 inverters, 30V power supply, stethoscope, IR detector, 6-channel disco lights, batteries charger, roadrunner, etc. and now this one).

The authors of the above claimed that their circuit works.
I had fixes for them all.

That is quite a boast. You suggested changes but did you even heat a solder iron on one of them? It is easy to suggest changes to a circuit and still have it work.
I have seen no confirmation that you fixed anything on this site. However, I have seen you boast that you taught Phillips semiconductor everything they know about transistors. And I am sure some day we will hear you boast how you fixed everything on this site. :
But tell me, what degree of electronics education does one show when he argues that "current" can be stored in a capacitor?

By the way: You just made a high pass filter. The resistance between the probes combined with the capacitor you have added. A small change to you, but a big design change in how the circuit will react.

MP

 

[MP1]

The author recently told me that he may update his circuit with my improvements when he has time in a couple of months.

Please post the e-mail thread for us to see. I am curious how he worded this.

MP

 

[audioguru2]

By the way: You just made a high pass filter. The resistance between the probes combined with the capacitor you have added. small change to you, but a big design change in how the circuit will react.

MP,
Where is the high-pass filter?
Since when can a high-pass filter create a voltage pulse delay?
I have been telling you all along that the circuit needs a delay, so that it can perform PWM on the NAND gate, causing the LED to dim.

Maybe you don't understand the difference between a high-pass or low-pass filter, like your mis-understanding of NAND gate logic. Perhaps your translation software is giving you difficulties.

But the capacitor that I have added creates a LOW-PASS filter, since it integrates the signal from the probe, and causes a delay.
That small change will allow the project to work properly.

 

[audioguru2]

MP,
Sorry, no disrespect, but please make accurate statements.

You don't believe that I corresponded with the author of this project? How's this:

Hello,
thank you for your suggestion.

I will try the added capacitor and reconsider the whole circuit (which has been designed and prototyped more than 5 years ago and is no longer on my workbench).
Unfortunately, however, I will not be able to do so until July, as now I am very busy and electronics design is not my job but only a hobby.

In any case, thanks for choosing RED Free Circuit Designs

Flavio.

 

[MP1]

Here is what you said:

The author recently told me that he may update his circuit with my improvements when he has time in a couple of months.

But it would seem in your last post that he only agreed to try the circuit with your changes in a couple of months. This is a little different than stating that he will update the circuit with your improvements.

I had no doubt that you corresponded. Just the accuracy of the statement as retold by you. And as I see...

About the filter: Yes, I meant to type low pass and typed high. No big deal since I wanted to point out that you were creating a filter here. But the rest of my statement is not changed. You have added a lowpass filter which changes the function. ANY filtering here would cause me concern. Also, I understand digital very well, thank you, as I work and design in the digital world every day. I do not have a misunderstanding of how NAND gates work. You can keep your snyde remarks to yourself in areas that I moderate or see a quick lack of posts from yourself in them. I hope this is very clear to you since you have had a language barrier with me in the past. I have told you before that if you have an argument with me, you can do it in private message. This is your last warning about this. The forum is no place for your arguments or insult and this will not be tolerated.

MP

 

[audioguru2]

Here is what you said:



The author recently told me that he may update his circuit with my improvements when he has time in a couple of months.



But it would seem in your last post that he only agreed to try the circuit with your changes in a couple of months. This is a little different than stating that he will update the circuit with your improvements.

ANY filtering here would cause me concern.

MP,
I didn't say that the author WILL update the circuit with my improvements, I said that he MAY do so, which is what he says.

What is your concern about a filter in a Schmitt-trigger (with hysteresis) circuit? It makes a perfect time-delay, since the output responds exactly when the rising input voltage reaches its threshold.

 

[audioguru2]

To All,
I was going to build a bunch of these cheap circuits (with my improvements), but now I realise that LED brightening (dimming in reverse) is a lousy way to indicate soil dryness, as i explained earlier (and now I have an even better idea):

When looking at the LED today, can you determine whether its brightness is more than it was yesterday (I noticed that the LED was very dim yesterday), without having a standard LED to compare it to?
Therefore another improvement would be for it to have a numeric display! (or row of sequental LEDs)

I am certainly not going to use a complicated display circuit for a dumb plant!

My new idea is to have a flashing LED indicate soil dryness. When the soil is wet then the LED is off. As the soil dries, the LED begins flashing slowly. As the soil dries even more then the flashing-rate increases. When the soil is very dry then the flashing-rate will be so fast that the LED will appear to be on steadily.
The circuit will be simple and cheap (1 CMOS IC, a couple of resistors and capacitors). The flashing will keep the average current drain low, for long battery (2-3V) life. The probes will have AC across them, preventing plating-action and corrosion. It will not cause arguments about how it works. The circuit WILL work. I could use a bunch of these.
Any comments?

 

[MP1]

This is what I suggested you do in reply #8. We look forward to your circuit post.

MP

 

[ante1]

Audioguru,

As surveillance for a plant (dumb or not) it sounds like very good circuit. I have to agree on your thoughts about the form of message the first circuit gave. Your suggestion will of curse give a much clearer message. Even JLB:s application measuring salt concentration can perhaps benefit from the new circuit.
I say: fine by me!

Ante :

 

[audioguru2]

Thanks, Guys.
Another improvement:
A bi-colour LED that flashes Green when the soil is not too dry, and flashes quickly Red when the soil is very dry.

 

[ante1]

audioguru,

Why not! And it

 

[audioguru2]

Ante,
Ha, Ha, and S-O-S to you too.

 

[audioguru2]

To All,
Didn't anyone notice? The oscillator's frequency CANNOT increase when the soil's resistance also increases, as my idea requires:

My new idea is to have a flashing LED indicate soil dryness. When the soil is wet then the LED is off. As the soil dries, the LED begins flashing slowly. As the soil dries even more then the flashing-rate increases. When the soil is very dry then the flashing-rate will be so fast that the LED will appear to be on steadily.

So I'll try the original circuit with an added delay capacitor and a new 74HC132 to replace the old 4093. I'll report my findings.

 

[audioguru2]

To All,
I built my slightly modified project and it works very well. ;D ;D ;D
The LED is very dim when the plant's soil is wet, gets brighter as the soil dries and shines brightly when the soil is dry.
I built the original circuit and it didn't work unless the supply voltage was 3.5V or more, because I couldn't find a Motorola 4093 chip (I used a TI CD4093 instead). The LED didn't dim, but was simply switched on or off when the soil's resistance was below or above 55K Ohms. With a supply voltage of 3.5V, the LED was very dim, when on. :'( :'( :'(
The slightly modified circuit works with a supply voltage of down to 1.8V or less (the LED's forward voltage). The CD74HC132 chip has so much drive current with a supply voltage of 3V, that I had to add a current-limiting resistor in series with the LED. With the trim-pot set to maximum (100K), the LED is off when the soil's resistance is less than 430 Ohms, it is very dim at 470 Ohms and brightens gradually as the soil's resistance increases to 56K Ohms where it draws an average current of 8mA. Above 56K to open-circuit, the LED stays bright. With wet soil between the probes (or a short-circuit), the circuit draws a supply current of only 0.2mA. The alternating voltage across the probes is exactly symmetrical, to avoid a plating action or corrosion of them. See my pics:

View attachment 35409

 

[audioguru2]

Wet soil, but not soaked:

View attachment 35410

 

[audioguru2]

Dry soil, this plant needs a drink, NOW:

View attachment 35411

 

[audioguru2]

My latest schematic:

View attachment 35412

 

[audioguru2]

Now all I have to do is change R4 into a regulated current source, so that the LED's brightness doesn't reduce when the battery's voltage runs down.