Thursday, 27 November 2014

Mirobot madness

Following the success of the DIY gamer I've been thinking about what projects might be possible at future CodeClubs.

Earlier this year I funded Mirobot - a wifi robot based around Arduino - and last week it arrived. A wet Sunday afternoon seemed the perfect time for may son and I to have a crack at it.

The main PCB is beautifully manufactured and perfect for young solderers. The instructions are very clear and easy to follow. The issue we encountered is that they never tell you to install the stepper controller IC (although it is shown in some of the pictures).  Working together it took about 45 minutes to get the main PCB and battery pack assembled. I liked that you could perform a useful confidence test by checking the Arduino leds prior to soldering the pack.

With the electronics bit complete, it is time to put together the chassis. All the parts come on 6 laser-cut boards. The componets should easily pop out but I found that some of the smaller parts were quite difficult to extract. Some of them are quite narrow and I needed to go over some of the cuts with a stanley knife to allow them to come away cleanly. My son was struggling and was worried that he would damage some of the delicate pieces. Although the material looks like wood it is really MDF and handles and behaves like thick cardboard: it can easily be torn and split.

I think if I was going to have a larger group of children assemble Mirobot kits I'd be tempted to extract all the pieces from the boards in advance.

The instructions note that the wifi antenna mount is fragile and I found it quite tricky to insert the rigid plastic aerial through the small piece of MDF. The sides are only a couple of mm thick in places and could be easily ruptured. Even with my (relatively) steady hands, some of the pieces came free leaving a layer of MDF behind. I fear that young impatient hands might struggle to complete this step without incident.

As you'd expect, until you get three sides on the chassis it is all a bit wobbly and I wondered whether the finished would need some wood glue to help its structural integrity. However the Mirobot uses an ingenious system of wedges to lock everything into place and the completed unit feels surprisingly sturdy (although I do wonder how long before the transparent wedges come loose and disappear up the hoover). My son is master Lego builder but even he needed an extra pair of hands to hold everything together for some steps.

Once everything is assembled, getting started is super fast. The built-in wifi makes its easy to use a tablet or phone to quickly confirm that everything is working in a few seconds.

However I did find that the connection to the Mirobot sometimes dropped out and the red 'reconnecting message' became a constant presence. I tried configuring the Mirobot to join my home wifi network but although that was successful, it didn't stop the dropped connection problem.

Eventually I seemed to find a workaround which was to keep a ping running from my laptop to the Mirobot. This is a trick I used to overcome issues with wifi dongles on Raspberry Pis suffering from power management issues.

This is a minor niggle and the Mirobot is a great little robot project. As part of the Kickstarter stretch goals I received the add-on kit too which includes a collision sensor which, if our initial tests are anything to go by, will be a useful upgrade. Hopefully we'll be able to get that up and running this weekend.


  1. Hi Richard,
    It's great to see you enjoyed building Mirobot. The Kickstarter has been really helpful in building my understanding of what needs to be improved with Mirobot and details like these are great.

    You're not the first to say about a few of these issues and some of them have already been addressed:

    - I've updated the docs to give better instructions about the stepper driver chip

    - The issue with the parts coming out was caused by me learning how to laser cut properly! I've implemented a more cautious cleaning strategy now so this should no longer happen

    - The antenna mount instructions have been updated (not sure when you built yours) to a better method which is less risky, but the antenna is my least favourite part of the design. I'm working on eliminating it completely for the next major version.

    - Regarding the dropped connection problem, it would be great if you could send more details to - I had considered adding a "ping" to the UI so that it would send data periodically to make sure the connection stays open. Not sure if this will fix it but I might ask you to test it and see if it does.

    - The pegs are a tricky one to fix. One of the design goals is that it should be easy to disassemble. This is for a couple of reasons; if a child assembles it incorrectly, it should be possible to take it apart and fix the mistake and if a school gets some, they can take them apart and other pupils can build them. I'm experimenting with other approaches, but so far all of them have caused excessive wear at the peg point (pegs with a notch that lock into place for example). I'll keep experimenting but this is why you get 4 spare pegs with the kit :-) Let me know if you need any more.

    Ben (Mirobot creator)