Thanks for your comments.
I found a solution. It was not obvious, and somewhat contradicted any instructions that came with the device.
For the BL-MP01, you need to put the selector switch to “AP Mode”. Once you do this, then different setup screens become available in the web configuration screens. There is a new screen called WDS (Wireless Distribution System) which allows you to select “Bridge Mode”. I think this WDS is intended mainly for setting up multiple APs to act as a single wireless network with one SSID – so in my mind bridge mode doesn’t really fit on this screen, but maybe something was lost in translation or I’m missing something. Anyway, once Bridge mode is selected, enter in the MAC ID of your main wireless AP, the WPA2 key, set up the BL-MP01 to use the same channel as the main AP. Reboot, connect the mini-router to the opensprinkler, leaving it set to ‘AP mode’ on the selector switch.
Once I did this, then DHCP worked and the opensprinkler received a 192.168.15.nnn ip from my main router DHCP server. The ‘routing’ function seemed to be disabled, and I can connect through my normal PCs now without issues caused by multiple networks.
Thanks again for the help.
Regards,
Glen