Wednesday, July 27, 2011

It Seemed Like a Good Idea at the Time...

So, today was supposed to be the day I tackled mobile power on the robot... You know, getting this thing to drive around without a tail.

I decided the best way to do this would be to build my own power supply, running off the 24V batteries from the wheelchair... Great Idea! Right? ... No.

Two fires later, I've learned I am absolutely not an authority when it comes to building power supplies... In fact, I could easily give lessons, quite well, on how NOT to build a power supply.

The real problem was I bought this great little case enclosure for all of my electronics, and thought to my self, "You MUST build a power supply that will fit within this box, alongside the Arduino and Interface controller to drive the chair." Afterall, a robot isn't a robot unless its purty as well.

I bought myself the wrong size capacitors, which caused one to blow up... LITERALLY. I didn't even know that was possible.

After I beefed those up, I plugged in the joystick, using a stick to turn on the power supply... (That should have been the first red flag, no? I mean... if you don't even want to touch what you just built...) To my surprise, the power supply came to life! Hooray!... Or, wait, no. Why does it smell like smoke? Apparently I shorted out the ground to the joystick and the actual wheel chair joystick was now on fire.

After quickly turning off power and assessing damage, it appeared to have just been a wire that burnt up... cleaned that up, replaced the wire and the chair now starts again... with out my power supply.

I'm in the process of finding the short now, and then will start looking for a bigger stick to turn it on.

1 comment:

  1. For all those you are reading this post and thinking of doing the same thing to their power chair. Instead of purchasing or making a power supply from scratch, I have made a home built bench power supply taken from a couple of old computers. They are beefy (18 amps on the 12 volt line in my case) - have built in regulation and free! In my case I bridged the two 12 volt supplies for 24 volts -WARNING.. and this only applies if you bridge voltages- make sure that you open at lease one of the power supplies and remove or cut the green ground wire. If you don't you will have a common ground between the two supplies when you plug them into the house plug - this will result in a short to ground if you bridge your two 12volts in series to make 24 volts. This made it a lot easier to work on interfacing the arduino with the chair's joystick -- getting it to work with your specific chair without purchasing batteries right away. Hope this helps!