is to possible to read only from secondary node in mongodb atlas?

I just started using mongodb atlas M0 free tier and it has 3 nodes (primary and two secondary) with 500 concurrent connection limit per node.I am building a web application in php and want to use primary node to write data using admin panel and secondary nodes to only read data from client applications.My goal is to increase number of concurrent reads using (500 * 500 = 1000) secondary nodes combined.Is it possible?.I use this string to connect using mongodb php driver "mongodb+srv://username:password@cluster0.***.mongodb.net/?retryWrites=true&w=majority".I believe this string does not explicitly connect to desired secondary node.Please let me know how i can connect to secondary nodes only for read operation.