@yoshi824 Most of us have been where you are now!
I suggest that you try to see the patterns in the code that you have working and try to make the SHT30 work from what you learn.
If it does not work as you want then post here the full code you have and what it is/isn't doing and you should get some help.
@Sunseeker According to the Connecting the Radio page, D2 is the default pin for the CE signal for the NRF24. If you'd like to use this pin for I2C, you can free it up by assigning a different pin for the CE signal by adding this line to your sketch:
#define MY_RF24_CE_PIN pin
IIRC, all available pins should work for this purpose (D0, D3, D4). Just pick one and if it doesn't work, use one of the other pins. Please make sure to add that line before #include <MySensors.h>.
@TheoL Not only did I put in delays, too, but I put in delays that were based upon the ID (which was stored in NVRAM)! This helped.
caveat: This is probably not accurate be helps to explain the challenges with a large network.
My initial experience with Arduino/nRF24 was using the libraries from TMRh20. Those libraries allowed a node to be a repeater, but only for 6 nodes. The primary node 0, master, only allowed 6 nodes to connect to it. The nodes connected to it also allowed 6 nodes. Subsequent nodes had to go through one of these repeating nodes. But the depth was only 4 deep. The master assigned node IDs if the node didn't already have one; similar to a MAC address.
The master also kept track of the addresses (ARP table?). Addresses were 4 octets (base in the form of D/C/B/A. A node connected directly to the master had an address of 0/0/0/a (where 0/0/0/0 was reserved for the master). A node connected through another node had an address of 0/0/b/a, and so forth.
But what happens is that a parent node has to mange the data from all its child nodes and their child nodes and their child nodes. Thus a node would get so bogged down dealing with this traffic that it din't do its sensor task very well.
It is my belief that MySensors either uses TMRh20's libraries or has developed some aspects based on his initial work. I see that that TMRh20 has a version 2 and I have not experimented with it. I did find that MySensors worked better than version 1.
Thus, my curiosity.
I am also duly impressed at the magnitude of hardware. Currently a nano like device from Aliexperss is US$2-3, nRF24 ~ US$1, power supply ~ US$1.50, power cord ?, case?, sensors!? While the hardware cost is daunting, even with a PCB it's a lot of work building those up. So, yeah, I'm impressed!
-OSD
The choice of MOSFET can be tricky. Seems that irlz44n was discontinued so you may need to find one adapted to the voltage and current you want to handle.
In all the cases you need to get a logic MOSFET too, meaning that they are fully open usually around 1 to 3V.
Also I'm sort of confused as it seems to me that L7812CV is a Voltage regulator, not a MOSFET. So if you are actually using that in the MOSFET spot it will definitively not work.
Especially if you are handling high current or voltage I would recommend using one from a reputable source for your MOSFET, I recently switched from mouser / digikey / aliexpress to mostly use http://www.arrow.com as you get free regular shipping, event if you order a couple of components (no affiliation to them whatsoever).
