Help me for my NRF24L01 Problem !!

I want to create a star network communication like image below ! 

one Arduino Mega 2560 + Ethernet shield + SD Card and NRF24L01 !! 

and some nodes up to 20 node. that contain Arduino Uno + NRF24L01 for create my project that server decide to each node have to start power on some device like LED ! and the nodes send some information for example temperature or humidity . 

what I have to do ??
 

 

First of all, I am having a difficulty in understanding your question. You are aiming to create a star network communication with those tools right? There is a slight problem based on previous projects about this, The shield + nrf24l01 have some problems in its compatibility. Well, if you have those components already I think the arduino and the shield can be mounted on top of each other. Same goes with the sd card shield. http://shanes.net/how-to-use-an-nrf24l01-rf24-with-an-arduino-ethernet-shield/

The communication process would be the challenge here. Can you show us your code for this?

I appreciate you. now I don't have specific code .

Are you recommend me to use SPI to Serial Converter module in below link ?

http://www.iran-module.ir/product_info.php/products_id/1887/language/en

to solve that SPI Communication problem with Serial .

There is quite a bit of information on the web,
try"using the nrf24l01 in star network" and you will get a number of hits.
If you are only needing to transmit things like temperature on an hourly basis, where you have plenty of time, you could set up each node on receive, and interrogate them sequentially, using the the transceivers address feature, each node would have a unique address, but would send to the master with a common address. This avoids the issue of collision avoidance or detection, and allows for re transmission on data failure. The range of the modules is not great, you would have to rely on directional antenna for better range. It is also possible to use the nodes to pass on data to the master, if, they were, for example, stretched out in a more linear fashion, but that may add an unnecessary layer of complication.
Another alternative is LoRa WAN, designed for low power, low speed data transmission for much greater distances, in large networks,
cheers,
Richard