audioguru Posted October 9, 2004 Report Share Posted October 9, 2004 Hi Oli,The "non-soil" is called Pearlite or Vermiculite. I doubt if it is conductive. I have seen potted plants growing in that light-weight white stuff.Don't you think that my circuit will fail if they were watered with "pure" water? Quote Link to comment Share on other sites More sharing options...
Olihou Posted October 10, 2004 Report Share Posted October 10, 2004 Hi AudioguruOf course not as, any pure water getting into contact with the dirty soil will become not pure. Minerals in the soil will certainly be dissolved in water.I wonder if there is any "soil" without minerals. If there is, then it is not suitable for plants -- plants need nutritions like N, P and K. They are normally in the form of soluable minerals in soils.I would very much like to hear any encounter of situation that the circuit fails. ::)Thanks.Oli Quote Link to comment Share on other sites More sharing options...
dicky Posted October 23, 2004 Report Share Posted October 23, 2004 If you place a 5K or 2K [depending on the current in the circuit]t-pot in the LED circuit you can alter the threshold of operation of the LED and dimming will occur. I haven't seen the circuit so I may be talking thru my hat......Dicky Quote Link to comment Share on other sites More sharing options...
Olihou Posted October 24, 2004 Report Share Posted October 24, 2004 Hello dickyDimming by a trim-pot? What do you mean? What do you want to do?Oli? Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 25, 2004 Report Share Posted October 25, 2004 How can I reply when the moderator keeps deleting my posts!The Plants Watering Watcher-2 circuit dims the LED with pulse-width-modulation. The LED doesn't have a threshold voltage, it dims smoothly from very bright to fully-off, depending on the AC impedance of the soil. Quote Link to comment Share on other sites More sharing options...
dicky Posted October 25, 2004 Report Share Posted October 25, 2004 I've just downloaded the circuits for the watering watcher..I read the text where it says A square wave is used to avoid oxidisation..my knowledge as an "improver" allows me to think that electrolysis would be the enemy of the probes..can some one explain why a sine wave is US and why oxidation not electrolysis is the nemesis of electrodes [probes]..browsing down the responses on soil conductivity...the main component of vermiculite is mica a fantastic heat and electrical insulator.. thanks guru.....dicky Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 25, 2004 Report Share Posted October 25, 2004 Hi Dicky,The waveform between the probes is a fairly symmetrical signal to avoid the plating/deplating action that would occur with DC or asymmetry. I don't think that sine-wave or square-wave would make any difference, as long as it is symmetrical so that the average voltage is zero. Quote Link to comment Share on other sites More sharing options...
dicky Posted October 25, 2004 Report Share Posted October 25, 2004 have seen ...thanks....dicky Quote Link to comment Share on other sites More sharing options...
Codyhtml Posted March 27, 2006 Report Share Posted March 27, 2006 Pure water is actually very acidic a simiconductor factory in my town uses water that has been striped of ALL minerals and the water is so thirsty for minerals that it will actually work like an acid so if someone watered a plant with "pure" water it would probably disolve the probes and the pot lol Quote Link to comment Share on other sites More sharing options...
audioguru Posted March 28, 2006 Report Share Posted March 28, 2006 Hi Cody,My tap-water has enough salts and minerals in it that it causes my Plants Watering Watcher-2 circuits to measure the same as a 47 ohm resistor between the probes. The water isn't acidic, it has dissolved conductive salts and minerals in it. "Pure" water doesn't conduct electricity and is made with distillation. Distilled water in dirt with plant fertilizer conducts fine for the circuit to indicate the amount of dryness.My probes are just tinned copper and corrode a little. I sand and re-tin them each time (6 months to 1 year) that I replace the battery. Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 8, 2006 Report Share Posted December 8, 2006 With your second circuit that has the blinking led, how would you modify it so you can have a lininer output with moisture vs voltage. would it be simmilar to the configuration of circuit one where the output does not blink. my objective is to try and connect this to the analog port on my microcontroller. Any help would be greatly appriciated Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 8, 2006 Report Share Posted December 8, 2006 Hi Satty,Welcome to our forum. ;DThe circuit of the Plants Watering Watcher-2 produces a logarithmic output so it shows a very wide range of moisture levels. It would be difficult to make it linear, so use your microcontroller to convert from logarithmic to linear.I have removed its blinking oscillator and LED driver transistors, and filtered the PWM at its output for you: Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 8, 2006 Report Share Posted December 8, 2006 thanks alot that will help me tons. Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 8, 2006 Report Share Posted December 8, 2006 one more question in the new circuit that you just posted ic1-c the output is not being used is that i miss print or is it just not being used. Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 9, 2006 Report Share Posted December 9, 2006 IC1c was the blinking oscillator. It isn't used so I disabled it by connecting both inputs high. Connect nothing to its output. Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 9, 2006 Report Share Posted December 9, 2006 cool thanks for the help i think i am going to start gathering some parts and testing. Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 18, 2006 Report Share Posted December 18, 2006 with this modification to the circuit what should i expect my output voltage range to be, i am not getting that good output. i have a range from 2.11V to 4.56V Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 18, 2006 Report Share Posted December 18, 2006 If you short the probes together the output voltage should be very low, close to 0.00V. My damp soil measures the same as a 47 ohm resistor and probably would make the voltage of your circuit very low.Try measuring the voltage with only a multimeter because maybe your microcontroller is pulling up the voltage. Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 18, 2006 Report Share Posted December 18, 2006 i was weasuring it with a multimeter and when i shorted the leads i got the max voltage of 4.65 Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 18, 2006 Report Share Posted December 18, 2006 OOps, thats right. When the soil is damp then the LED is off so the output of the gate is high. You can't increase the value of R8 from 47k or the output voltage folds and works like a mirror. The circuit will need an opamp to shift the output voltage from 0.0V to 5.0V. Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 19, 2006 Report Share Posted December 19, 2006 another question the circuit seems to latch in the high state and when i abruptsl contact the probes together it goes back to the low state. My high state shorted probes is 4.65v and my low state high-z on the probes is 2.12v does this seem reasonable. I also had another question in my case i am only looking for 3 threshhold DC voltages to trigger watering, so my microcontroller will be looking for only 3 set dc voltages. Would it be easier to use the soils resistance to adjust the gain on an op amp producing a range of values based on my op amps gain. Almost like a thermister would be used for temperature. Im not doing data logging so i only need minimal accuracy say dry, medium dry, and wet. But if the output from your design is supposed to be from 2.11 - 4.65V and i van get rid of that latching effect then i can make that work. Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 19, 2006 Report Share Posted December 19, 2006 Hi Satty,I have made many of these projects and they don't "latch". Did you substitute any parts?Maybe it does something funny with a 5V supply. I can have a 100k pot beween the probes and the LED is off when the pot is zero ohms to 47 ohms then it gradually gets brighter until the pot is 100k or is not there.Another member wanted 3 coloured LEDs to indicate the moisture level of the soil. We designed a circuit similar to yours but with opamps as comparators to drive the LEDs: Quote Link to comment Share on other sites More sharing options...
sattyshack Posted December 19, 2006 Report Share Posted December 19, 2006 i used all parts the same as specified accept on the electriltic input cap i used a 50V because i didnt have a 16v but that i dont think would matter. i also used ceramic disc caps for all other that still shouldnt matter right? Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 19, 2006 Report Share Posted December 19, 2006 Your capacitors are fine. Quote Link to comment Share on other sites More sharing options...
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