lowest cost node

[jayjaytocool]

yes im a noob. I have a couple questions. do all the nodes have to have there own board like a nano or uno? if so can one be made cheeper using a chip? I would like to build a network with a couple hundred nodes that have 2 inputs and one output. input1=temp input2=switch output=relay. what would be the cheeps way to build a wireless node? as u can see cost of a couple hundered would add up quick. is 10-20$ doable? thank u all. love the site so far. l'm pretty new to all of this but finding the iot is quickly becoming my new number one hobby.
oh also do I need a gateway using a uno r3?

[jayjaytocool]

@jayjaytocool forgot to mention I have 10 nf24l01 2 uno r3 and one raspberry pi 3 as well as a uno r3 most complete starter kit to work with. hope u guys don't mind giving me a little kick start

[Nca78]

Hello,

yes it's possible to work with an atmega328 chip only without the arduino board. But then you need to put external components to make it work so you assembly time will rise.
Lowest price is 1.2$ atmega328 + 1$ nrf24 + 1$ PCB + 0.5$ extra components and I would add 1$ for atsha signing component (to sign messages and avoid hacking of your network).
That's less than 5$ for a "base" node.
The rest depend on the type of node you want to implement: from main power or on battery and then what battery life do you expect, what precision you expect from temperature sensor, what load you want to control with the relay etc etc

[gohan]

Are you trying to automate an hotel? With a network that large you will need to use a lot of transmission error checking in the code unless you are going to segment it in smaller network.

[mfalkvidd]

Cost can be affected a lot by how you value your time. If your time is endless and free, you could learn how to design and build custom nodes quite cheaply.

If your time is not free, going with something like the sensebender would get you a long way for $14. There are also a lot of other nice boards on openhardware.io.

In any case I would advice to start small. Set up one node and one gateway using the components you already have at home. For the gateway you can wire a nrf24 directly to the gpio pins on the raspberry pi, instructions at https://www.mysensors.org/build/raspberry
For a node you can use a nrf24 and an Uno. See the build pages for ideas and instructions. When that's up and running you'll probably have a good idea on what the next step can be.

[jayjaytocool]

Thank you for the help. I'll start with the pi and no for the gateway and the uno with a nf for the nodes. I ordered some nanos last night pretty cheep 5for 12$ I think. I'll try them after and then maybe move on to the chip. I agree time is worth a lot. I planning on trying to automate the watering for a commercial green house. With independent control over each site. I saw the gardino and other builds but nothing quite like what I have in mind.
Any recommendations for the controller?

[jayjaytocool]

@jayjaytocool I would like it to sense a defined moisture content in the soil then open a solenoid valve till water is sensed at the drain. I would also like it to only water from morning to noon. So if it's needs water at 4pm it waits till morning to water. Also I would like there to be an off delay. So water is alowed to continue flowing for x time after water is sensed at the drain. One greenhouse can have 500-100 plants. So u can see my concern with cost. Either way I think it will be fun to try. Great forum thanks for all the information and help

[gohan]

As long as you have sensors and you can read data, you can use that data to be used in rules in the controller. Domoticz for example has a rule creator that also uses blockly that is very useful when you are not much into programming.
If you need to check moisture levels (analog sensor) and water present (as a digital input), you could check 6-8 plants with a simple arduino or 16 using a Mega 2560.