HW startup: A journey from (Arduino) idea to product
hwstartup.wordpress.com
hwstartup.wordpress.com
1) don't different plants need different amount of moisture in the soil? How do you account for that?
2) why does moistly check the moisture levels so frequently? Wouldn't hourly or even daily be more than enough? I assume partly you are checking regularly because the alarm shouldn't go off after you've done the watering, but what about checking regularly if the last check was 'dry', but not as regularly if the last check was 'wet'?
To answer your question: 1) Yes, they do. But by measuring the moisture in the soil, you will get an alarm when a certain amount of water is extracted from the soil, being caused by heat, sun or a thirsty plant. After quite a bit of experimentation, we found a threshold value that works for most plants. Not cactuses ;) 2) Indeed we check more often than needed. But if the plant is getting dry, we want to briefly signal every five minutes and before we do that, we do a quick soil check.
As an arduino noob, it wasn't clear to me why you need a resonator component, especially since it isn't present in your first schematic?
Also, have you given thought to what happens after the battery runs out? Can the battery be replaced by the customer or does the device need to be disposed of?
The resonator is shown in the 'Eagle schematic', right in the middle of the picture. The first schematic is just for the moisture sensor. I used it as a crystal to run the ATMEGA.
When the battery is gone, you just pop open the enclosure and put in a new CR2032 coin cell battery. You can get those at every gas station or supermarket.
So an ATMEGA uC needs an external oscillator to run? Is it to provide the clock signal or for something else? If so, why doesn't it have its own clock signal generator? Wouldn't it always need one to run at all?
Edit: Also can't check out in Chrome… just sits in 'Completeing Order'