Project – Hybrid Wireless Router / Power Splitter Box
A while back, I posted about using Skysafari to control your EQMOD interfaced mount via a wonderful little utility known as ‘WiFi Scope’. In order to do this, you need some sort of wireless connection between an iPad/iphone and your laptop running EQMOD. At the time, I was using a technique called ‘Ad-Hoc’ networking, which enabled the iPad and laptop to communicate with no intermediate device involved. This, in theory, was a great way to do things. Unfortunately, in practice, it turned out to be just a bit frustrating. You see, theres a major problem with the implementation of Ad-Hoc networking in Windows – it’s rubbish!
Suffice to say Windows ad-hoc networking is about a stable as a raspberry jelly. The problem is, when it worked, it worked well, but when it stopped, then it would just REFUSE to allow reconnection to happen. This would mean restarting the laptop to bring it back, which lost me my 3-point alignment, and all my other tweaked settings. Remember I’m running on a mobile setup, rather than in a nice observatory, so have to redo my ago-to alignment every time.
Anyway – to cut a long story short, I came across a lovely little device for just £16 – the TP-link WR702N wireless router. There are several things that caught my eye with this little beauty…
- It’s CHEAP!
- It’s SMALL!
- It’s USB-powered.
They’re all important, but I’d say that the last one is almost the most important in this case. Yes – it can be powered via a standard micro-USB connection. This means you can actually power it from the laptop you use to connect to it if you really want to! The power consumption is tiny – 0.07A (see the multimeter pic below).
I hooked it up to the output end of an LM2596 Step-Down power converter board (available from eBay for a quid or two each – do a search), with the input end linked directly into the input of my power box. After dialling back the output of the board to 5v using a multimeter (via the little brass screw), I connected up the router (via it’s cannibalised down power cable), and voila! I had a router that could be powered of my leisure battery that was small enough to be housed completely inside the home-made power box I used to power my whole setup with the help of a bit of hot melt glue and velcro.
Take look below for a gallery of the process. Once complete, I simply connected my laptop and iPad to the WiFi network, followed the instructions to set it to ‘Router’ mode (which even though not strictly needed, means that it will dish out IP addresses to everything as necessary). It doesn’t do any routing as such, just allows devices to connect to it and talk to each other over the resultant network. I gave the WiFi network a sensible name and defined a WPA2 key. Last step was to reserve the IP address for my laptop so that it got the same one every time, so the IP I punched into SkySafari to connect it to WiFiScope (the IP address of the laptop) never changes.
This is also compatible with Android phones and tables running SkySafari – these aren’t able to do Ad-Hoc networking at all, so the previous way I did it was iOS-only.
The upshot of this is that whenever there is power to my power splitter box, I have a WiFi network available to connect my devices to – perfect out in the field. The difference to battery life is absolutely negligible, and it works 100% perfectly – not had a single issue with it.