Thanks for your reply Brad,I suppose you plan to broadcast ultrasonic noise first? So you can detect echoes from plants which are at 20-60 cm height? Causing a solenoid to turn on the sprayer?
(Or you might choose a high-tech radar type of detector which works on ultrasound (or else radio waves), as might be used on automobiles to avert collisions.)
Or it may work better to detect plants optically. Say you mount a camera at knee height, and if it detects a plant directly in your path, the sprayer activates? A camera aimed at the sky would detect a plant as slight dimming of the light.
This sounds really cool. Sounds like it could work. However I can't stress how amateur I am when it come to things like this but a bit of practice will do no harm.A single photo-sensor at ankle height would get dimmed as it nears a clump of the dark green weeds. Aim it at an angle to produce maximum contrast whenever a weed clump blocks the sky.
The electronics could consist of an op amp, powering a transistor, which in turn powers a relay, which in turn powers a solenoid. (I guess your word 'replys' refers to relays in post #1?)
Various inexpensive photosensors are an option. Cadmium sulfide cell, solar cell, phototransistor, photodiode, Infra-Red receiver (this last component resembles an led).
The circuit (first stage of amplification, that is) is a simple project we'd find in a grade-school '100-in-1 projects' electronics trainer. Simply adjust the trigger point between bright/dark level.
The remainder: transistor, relay, solenoid are needed to step up the power to operate a nozzle. It requires familiarity working with such components.
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The second picture shows broad leaves which are bright and glossy. They look like they shine in sunlight.
For these, a photosensor at knee height, aimed downward. Adjust op amp threshold so it turns on when exposed to brighter light.
file:///private/var/folders/3t/y0_r7y0d46lcd9hm7h8ll0kh0000gp/T/AppTranslocation/B63A955F-147E-47FA-B4D2-1B4CFA064424/d/CircuitJS1.app/Contents/Resources/app/war/circuitjs.html?ctz=CQAgjCAMB0l3BWEDoBYEE4AcYFwMz5iqoBMqIA7JMsjQgKYC0YYAUPpRfqTeTTwGQKNGADYsPEABkAlgHMAFgBcAOgGcAQgCcFKgHYN16ttpCDwlMed4h+UO7zht5Nod1sXRbZSFRhre1QxCnsaCBYYK2JITjE4UjwxCHEcZOIxUlYAsHwscDgQABMGADMAQwBXABtlFz8QuwRrYI9RKDYAdz8sPkpSHr5yDtdMAdJ+5AwBrw6wSnzUDGtiCiXA4ZWoaAGYSAmsJdI8jHmMVEkSbcgkMHh4a-HRWFxrm-A2ACU3S2sLVl2DlQ4UBzwQXwaFFWkPAYFBfhBDjBEPW4CuqIBSIR4HhMHBZgsQQCdmBDju8C6gzskwQcOpuzYYBwyDpEwGY3pZLE8TQmGBlH6XFylBx4GsexSLzYAA9kPgkKRsMheuZIBBQhRqgB7cpFNhahyNGjAjAisA7JB7OALOGWuwOfAgAAOii1yi12iMsnU7u0+vAjqNCKVnh2DgGuXMIG1urYQA
This is good stuff. It's much appreciated. Iv got some work to do. I will start out small with some testing and see how it goes.Simulation, light-dependent resistor (typical CdS photocell) controls a transistor which controls a relay which lights a bulb.
Since your supply is 12V, it provides sufficient power so your circuit can use robust components and fewer components.
The slider at right mimics dark/bright exposure on the photocell. When a weed patch darkens the sensor, its resistance rises, allowing the transistor to turn on.
View attachment 181403
Relays have different volt ratings. The relay coil must be rated 12V. As for the relay contacts, they must be rated for the maximum Amperes drawn by the load (solenoid).
For the bright glossy weeds you want the photocell to perform the opposite function it. To do this it may be feasible to connect the solenoid to the relay's other terminal. One SPDT switch can select between them.
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Copy and past the code below to (ignore message 'can't load circuit file''):
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Code:file:///private/var/folders/3t/y0_r7y0d46lcd9hm7h8ll0kh0000gp/T/AppTranslocation/B63A955F-147E-47FA-B4D2-1B4CFA064424/d/CircuitJS1.app/Contents/Resources/app/war/circuitjs.html?ctz=CQAgjCAMB0l3BWEDoBYEE4AcYFwMz5iqoBMqIA7JMsjQgKYC0YYAUPpRfqTeTTwGQKNGADYsPEABkAlgHMAFgBcAOgGcAQgCcFKgHYN16ttpCDwlMed4h+UO7zht5Nod1sXRbZSFRhre1QxCnsaCBYYK2JITjE4UjwxCHEcZOIxUlYAsHwscDgQABMGADMAQwBXABtlFz8QuwRrYI9RKDYAdz8sPkpSHr5yDtdMAdJ+5AwBrw6wSnzUDGtiCiXA4ZWoaAGYSAmsJdI8jHmMVEkSbcgkMHh4a-HRWFxrm-A2ACU3S2sLVl2DlQ4UBzwQXwaFFWkPAYFBfhBDjBEPW4CuqIBSIR4HhMHBZgsQQCdmBDju8C6gzskwQcOpuzYYBwyDpEwGY3pZLE8TQmGBlH6XFylBx4GsexSLzYAA9kPgkKRsMheuZIBBQhRqgB7cpFNhahyNGjAjAisA7JB7OALOGWuwOfAgAAOii1yi12iMsnU7u0+vAjqNCKVnh2DgGuXMIG1urYQA
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