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the main problem is that a moisture sensor needs the default state to be LED off then the LED should come on when no moisture is shorting the probes (plant needs watering). And this cor unit is doing the opposite.
Hi, Thank you GGOM20 and Iceng for helping me!Please see attached picture, in this circuit the LED is on (pretty dimly) by default and when the red probe leads are shorted, as they would be by moisture in the plant pot, the LED goes off.The problem is that a moisture sensor needs the default state to be LED off (otherwise battery will be flat) when the probes are shorted by sufficient moisture (plant doesn’t need water) and then the LED should come on when no moisture is shorting the probes (plant needs watering).Am I nearly there or shall I ‘bin it’?Thanks again
thank you, I have been busy for the last couple of days but hopefully tomorrow I will have another try - once again, thNk you all for tKing the time and trouble to help me. It is appreciated.
thanks again iceng, I will find copper tips.Just to clarify...in moist soil I want LED off and when dries out I need LED (and buzzer on). Do you think the coloured picture circuit which I posted is viable, because it iis not working. Thanks again
downunder35m, many thanks. I am afraid I have lost the ability to read circuits (even after being an apprentice TV engineer in the 60’s) so I need to cheat and follow a physical board layout or picture of one
Hi iceng, thanks for helping, the ‘circuit drawing’ which I am following has the LED turned OFF until the moisture at the bottom of the container gets too dry - then the LED and a buzzer will come ON. I intend to put two 18ins long plastic terminal posts inside the header box, then run the red terminal wires inside these plastic tubes and then solder the ends of the leads onto galvanised roofing felt nails at the end, push the nails back up the end of the terminal rods and seal. So that the flat galvanised head are the sensor tips.I have found an error in the drawing though - in the coloured drawing that transistor the NPN 2N2222 is shown as being, from left to right, looking at flat face, CEB....but in actual fact the tech info below says it is EBC(???)
we don’t have garage sales in UK, and wanted to make my own
sorry, out of practice posting
Here are the pictures - internet plan and air construction -
Could not gey pictures to publish, really tricky on indestructables!!!Can they be added now the subject has been published?Thanks
What are the values of the replacement LED you used?I have measured the voltage fed to the present LED and it is only 1.7volts.Thanks