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Plants wattering watcher


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Ok Hi i guess you forgot that you helped me modify this and i don't have a led i have a led bargraph display

I guess you built the circuit that I recommended earlier. The ICs and voltages are good and the LM3915 should be lighting a few LEDs. The number of lighted LEDs should be adjustable by turning the 2.5k trimpot.
Did you change any parts values?


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I don't think so except i didn't have a 510 ohm resistor and i made like a 500ohm or something so it should be fine and i think one other resistor i had to make my own but i came pretty close (by make my own i mean put two resistors in series)
i found two mistakes that i thought i made and fixed them i thought i hooked up the leds backward but when i switched them it didn't fix anything (oopa i'm dumb i had forgot to connect one on the ics to ground so i did that and switched the leds but i realy had the leds on right  ::) in the first place  looks like its time two switch them again :( lol

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i didn't have a 510 ohm resistor and i made like a 500ohm

The project does not have a 510 ohm resistor in it. Which resistor on the schematic?
R1= 470k, R2= 100k, R8= 47k and two resistor values and a 2.5k trimpot are shown on the modified schematic.

i thought i hooked up the leds backward ...


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Doesn't the circuit light any LEDs?

Please measure the voltages of pins 1 to pin 9 of the LM3915.
Please sketch how you connected your 2k pot and 510 ohm resistor.
What color and voltage are your LEDs?

Disconnect the cathode of an LED from the pin of the LM3915 and connect it to a 1k resistor with the other end of the resistor connected to ground. Does it light?

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ok pins 1-9 of the 3915
1| 3.8
2|.4MV(basically zero)
4|.4MV (same as 2)
5|.64 V
The Led's will light when not connected the the circuit
i saw that i had connected the pot wrong i corrected that and the leds would light but my leds are just misc. ones from my drawer and one of my red leds meaning dry is on always i don't know if it is the leds or the circuit because the other leds just dim when i adjust the pot until they are barely visable
i put in a switch to change between dot and bar and when it is in dot i don't see anything please help
EDIT: when in dot i do see one green led (second from first meaning wet) when the probes are dry
does the 3915 work high number down?

whoops i realy messed this project up :(
i connected pin 1 of the 3915 in the wrong spot i connected it next to the led for pin 10 on accident so that probably explanes some of the wierd things

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Hi Cody,
You have had a lot of things mixed-up in your circuit.
What kind of battery do you have? Is it strong enough to supply 80mA when all 10 LEDs are lighted in the bar mode and still have 5V or more?

On the LM3915, pin 7 and pin 8 should not have the same voltage like you have. Pin 7 should be about 3.5V and pin 8 should be 1.25V less which is 2.25V.

I designed the LM3915 connection to the Plants Watering Watcher-2 circuit so that with dry soil or nothing between the probes, then all 10 LEDs will light. When the soil is very wet or the probes are shorted together then no LEDs will be lighted. It can easily be the opposite if you want.

Your voltages show that the LM3915 should be lighting 7 LEDs when it is in the bar mode, or the 7th LED in the dot mode. If the voltage measurements were made with nothing between the probes then the trimpot should be adjusted so that all 10 LEDs or the 10th LED lights.

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