my kitty is getting better, hes eating and playing outside. we will finish up the antibiotics but i think the worst is over now.
i was just driving around a robot i cobbled together out of legos, and arduino, and some other crap i had lying around. for the transmitter im using an atmega 328 (programmed with arduino), mini joystick, and re transmitter along with a voltage regulator (power comes from a rechargeable 9v) and a crystal for the clock, some caps and an led. control is provided through a ps2 style thumbstick. it transmits a 5 byte packet with a 10101010 sync byte, a control byte with the first nibble containing button bits (only one so far), and the second the contains the most significant bits for the y and x axes. byte 3 and 4 contain the 8 least significant bits for the x and y axis, fifth byte is an xor checksum.
this packet is picked up on a reciever module, i had to use a logic level converter for the signal wire to boost it to 5v, i didnt have one so i used an opamp instead. this amplified signal goes into the arduino board's rx pin. im using the arduino's voltage regulators. power comes from a small 11.1v lithium polymer pack (the same one i use in the helicopter). i use the vin pin (battery voltage) to power an hbridge chip's motor power bus. the chip itself runs off of the arduino's 5v bus. to control the hbridge takes 2 digital out pins and a pwm pin controls the speed. i also have a servo connected to the 5v bus and one of the digital pins.
the chassis was built mostly from studless parts from my nxt set, with some small parts from elsewhere. im using one of the old skool 9v technic motors, it has almost no torque (~0.45 ncm) at all but can do 3300 rpm @ 12 volts. the vehicle is very light so it doesnt need much power. the chassis is a reverse trike with automotive style steering and a single drive wheel in back. the only drive reduction is about a 2/5 drop by pully and belt (really a rubber band). all the electronics and battery is held on a platform on top of the car and held down by rubber bands, kind of a hackish add on because the electronics turned out to be bigger than i had expected.
i spent the last two days trying different performance configurations originally it was powered by a single 9v rechargeable battery. this got upgraded to 2 in parallel but was still not giving me more than 5 minutes of drive time. i tried a newer lego gear motor (one from my old mindstorms 1.0 set) geared up 1.5 times via a chain drive. it had more torque but ran out of power faster. the speed was about the same, still too slow to be fun. so i put the old motor back in and tried gearing it down another 3/5ths in addition to the 2/5 pulley drop. it was added torque but that only made it slower. this is where i put the heli battery into it. i didnt change the gearing and it started to haul ass. but i figured with the motor pushing 11.1 volts, i decided to do away with the extra 3/5ths gear down, and its back to the original 2/5ths pully reduction. it gives the best balance of speed and torque. the end result, it ****ing hauls ass. i never thought id see something powered by that motor haul ass. i put a camera on it and ran a few laps around the kitchen island, using only the camera to see where i was going. the end result is pretty cool.
