Soil Moisture

http://www.ohmslawcalculator.com/555-astable-calculator

https://github.com/acolomitchi/cap-soil-moisture-v2/blob/master/square1-planecap/print/square1-planecap-inkscp.svg

http://www.instructables.com/id/Automatic-Watering-System-With-Capacitive-Probe-an/

https://electronics.stackexchange.com/questions/184845/how-do-you-measure-soil-moisture-using-a-capacitive-sensor

https://zerocharactersleft.blogspot.com.co/2011/11/pcb-as-capacitive-soil-moisture-sensor.html

https://github.com/Miceuz/PlantWateringAlarm

https://www.facebook.com/Plastidip-de-Colombia-802958523088359/?nr
https://articulo.mercadolibre.com.co/MCO-455777033-plasti-dip-tangerine-orange-plastidip-performix-brand-_JM