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Thread: Sparky!

  1. Sparky!

    The helpful people here at Trossen have always been great at replying to my threads and helping me out, now it's time to give back with some project documentation!

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    This is my first robot, Sparky. I eventually want it to be a fully autonomous pet robot. Ever since I saw Djsures' K-9 I knew I had to build something similar (djsures you're robots are awesome! I love how lifelike you make them, they have such great personality). I have high hopes for this little guy. Ultimately he will be self charging, fully autonomous, and interactive. Right now though, it doesn't do too much. I've spent the last couple months focusing on the basic frame, and some custom electronics. First was the frame, because testing is way easier when I don't have to worry about balancing all his electronics on top of one another . His frame is just some thing plywood I cut out with an exacto knife and drilled a bunch of holes in, it's held together with 4-40 bolts. Next came the electronics, and this part was a bit more complicated so I'll give it its own section.

    On-board Battery Charger:
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    I designed this board to help sparky manage his battery. The whole process took me about three months, but it was my first electronics project so I feel like I did pretty well. The circuit is based on the Max712 Nimh charger IC, and is specifically designed for an 8 cell Nimh pack. It combines a voltage sensor and a battery charger for a very effective power management solution. When the board gets power from an external source (DC power supply from wall) the board switches the robot to wall power and starts charging the battery. It also keeps the robot's microcontroller informed of whether or not the board has power, and lets it know when the battery is done charging. The onboard voltage sensor uses an op-amp to convert the battery's 8-18V to a 0-5v signal for the microcontroller. The batteries are charged at 1amp until full, and then subjected to a very light trickle until power is disconnected. The charger also controls a fan to keep the battery and board cool while fast charging. I have also included a switch in series with Vout so that the robot can be charged while turned off. For efficiency and run time, I have a 6v switching regulator between the Vout connection on the board and the microcontroller.

    IR Emitters/Detectors:
    This is the next step. Sparky needs some way to identify his charging station so he can dock with it. I'm going to build a simple 38khz IR beam emitter for the charging station, and a vaned IR detector for Sparky. I have all the parts, and the circuits are planned out, I just need to get to work.
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    Last edited by draikani; 09-29-2011 at 06:11 PM.

  2. Re: Sparky!

    I'm having some problems with my microcontroller. When I hook some of the pins to my charger it seems to be pulling those parts of the charger low. Do I need resistors between the circuit and the microcontroller? How much current do I need to allow into the microcontroller pin for proper sensing?

    This is unrelated, how do I determine the frequency of a signal on one of my microcontroller's digital pins? I've looked around a little but haven't quite found what I want. Maybe someone can point me the right way? Edit: only interested in frequencies under 1500hz.
    Last edited by draikani; 10-16-2011 at 11:33 PM.

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