Let's Make Robots!

Robot Baneblade

Navigate by ultrasonic sensors, track targets with moving turret via non-contact temp sensor, "shoot" with LEDs in the guns

A remote-controlled Baneblade for a HSC Software Design and development project, already done by BobPanda, thanks for the inspiration, but now with a little more functionality. This is for a school project, by the way. The idea is to get the tank to navigate by itself through ultrasonics, track body heat with the sensor mounted on a rotating turret (which will be a bitch to program, from what I've heard), and basically look awesome with LED cannons. Also, it can receive commands via an IR sensor, and because my classmate is making a universal remote for his project we can have an RC baneblade. It's very ambitious, but I'm hoping that I can do it and maybe even make it a Golden Daemon entry :-). P.S. sorry for image quality, taken with my iPhone.

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An "open collector" output is a digital output that pulls the line to ground when active - essentially it acts like (and often is) an NPN transistor with the output connected directly to the collector.

To use an open collector output as an input to a microcontroller or other digital input, you need a pull-up resistor to allow the output to go from low (when it's on) to high (when it's off again).
The open collector output acts a lot like a switch, in that when it's inactive the output line is left disconnected, also referred to as an "open" connection. The open connection is left "floating", with no power source driving it to be at a high or low voltage. Floating inputs are highly susceptible to noise and interference, and may result in erratic signals and/or false positive readings.
This is where the pull-up resistor comes in. When the open collector is active, the output is pulled low to ground, with the contribution made by the pull-up resistor (which connects the output to V+ via a high resistance, often 10-20kΩ) being swamped by the strength of the open collector. However when the open collector becomes inactive the pull-up resistor is able to pull the output line up to V+, providing a clean and reliable transition from high to low, which is seen on the microcontroller's digital input.

In short, you connect the output of the PIR to a digital input on your microcontroller, and then you connect a suitable resistor (10-20kΩ if in doubt, the PIR's datasheet may have a recommendation too) from the digital input to V+. Depending on which input you use, you may have pull-up resistors already connected, or you might be able to enable them internally (inside the PICAXE itself).

hi again, long time since my last post, but most of the body is done (picture on the way), and I have even mounted some of the lights. However, I have a problem. The Tamiya Twin Motor Gearbox I have been using (with the motors it came with) is just not powerful to move the tank, so I have been rather frustrated trying to get things going. Any suggestions as to track tension, correct gear ratios or what kind of gearmotors to use?

Before you go shopping for new parts, have you changed the gear order for the maximum reduction to increase the torque?

yeah, I was using 203:1 and that didnt do much, but then I realised that the tracks were getting caught on some internal cross-bars that are part of the model. I cut them out, and the tracks should run fine now. I say "should" because in my frustration I pretty much ruined the gearbox by running it despite the sticking tracks, and I need a new one :-(

That sucks =/

At least the photos are looking awesome =)

thanks! I'm trying to make it look reasonably ok, but if I can enter it into the Golden Daemon painting contest then so much the better

The tank body, with servo for the ultrasonic sensor, PIR on the upper body (left) and turret with some lights (top)

What the track system should look like (except it wont be as out-of-line as it is here)

Jesus christ that is bright! (green targeting light, red main cannon light and cool white searchlight). I even put the lens from an old optical mouse inside the turret so it looks extra bright from the front (the front view was way to bright for my camera to handle)

ok, so finally got the drive system mentally sorted, but now for the next bugbear; the Melexis temperature sensor. I know how to mount it, I have the wires, but thats it. The sample code is only for polulo controllers, so is there any chance that someone knows how to program this in basic, and wire it to a picaxe 28 project board? I would find this myself, but I have to go out now, and I have exam prep to handle for the next couple of weeks. :-(

so i was looking up some other baneblades that had been lit by their builders, and I noted some lights such as targeters that flashed every second or so, as if scanning for  targets. I know i can say something like, high 4, pause 500, low 4, pause 500, and loop it but there must be a better way to do this. Assuming the voltage drop across the LEDs is 4 volts,  a power supply of 4.5V and all the proper resistors are in place, is there some way to put a capacitor in place to produce the flashing effect?

Nope, the capacitor will just smooth out the supply to the LED, so it fades on and off instead of switching immediately.
If you really don't want to control the LED with your micro then you'll need some active components to make it flash - search google for "led flasher", "led blinker", etc, to find some of the easy ones that just use 2 transistors or an inverter chip.

Even easier would be to find some LEDs with built-in flasher circuitry. They're pretty common and cheap now, and you connect them just like a normal LED (power, resistor, ground), but they flash at a pre-determined rate all by themselves.