Be careful with an external timer! I know. I have an Aquabot turbo plus remote that I bought two years ago. Because, the plus remote model does not have the built in timer, Aquaprodocts supplied an external timer. The problem is the timer provided and every digital external timer I could find on the internet, goes on automatically every 24hrs. So if you leave the bot in the water and then someone takes it out of the water (which aquaproducts says to do if someone goes in to the pool) with out unplugging it, the bot will turn on and start running out of the water. If you are lucky, it will fall back into the water. Unfortunately in my case I was not lucky and the bot ran into my pool house and tried to climb its wall for 5 hrs. The first time this happened both drive motors and the pump motor burned out. Since the unit was only 2 weeks old, they reluctantly fixed it under warranty. This summer, the same thing happened. Only the pump motor burned out, but it cost me about $200 to fix. Also, again form experience you can not leave the PS outside uncovered. Again a design defect. I have mine on a stack of bricks and I cover it with a bucket.