Let's Make Robots!

"Halo" Xmas bauble edition.....

Projects a laser generated "Halo" on the floor .... as an object detect system

I present "Halo"  ..... my latest Laser Robot

It been almost a year now that i have had the idea to cast some form of "Halo" around a robot and detect the reflected signal.

               Then after playing with some motor driven angled mirrors and lasers .... the idea came, narrow down the resulting Laser circle and beam it around the Robot........

               I placed a Wii-Camera above the whole contraption and was able to capture the laser circle.....YAY.

The Wii-Camera is able to track the Laser at a good speed.

The system is still in experimental stage .... i just need some Plexy glass do-dadds (any ideas from the Laser cutting Gurus out there?) to make it "Round and Sound" ie to mount the Laser/motor/Wii to the robot.

When the laser beam is broken by an object or a "cliff" then it possible to detect a break in the circle picked up by the Wii-Camera.

This is just the start of a whole new concept for me..... still much processing to deal with.

Many robots rely on a sharp or ultrasonic sonar based systems or northsoutheastwest IR leds which are err i stick my head out here Low resolution.......the laser "Halo" system by my current ballpark calculation provides a 360° sweep circa 1024 points.

5mw Red laser works best.......(100mw Green - works .... Ultra-Violet laser - nada).

BTW ..... the tracked robot base does in fact work ...... just a question of squeezing the Wii-camera into the on board RBBB propeller system.

Update 4/11/11 :-

Just found out that pulsing the laser on and off gives a better environment for the wii-camera........

...... the wii camera works best when it can see single spots of light........pulsing the laser on and off provides this.....

Gives an interesting optical effect and shows how you can adjust the resolution by software.

It also speeds up the sampling  time

Low resolution .......

Medium resolution ........

UPDATE 5/11/11 :-

Now it turns out that a Red Xmas bauble can reduce the height of the laser pole YAY.

laser Circle still projected onto floor from above .... then Wii-Camera mounted on robot looking up at a Xmas Bauble.

The speed of the laser circle should be kept low......the wii camera can only track well at low speeds......

The Xmas bauble acts like a mirror / wide angle lens (its red colour helps to filter out none red colours :-) and picks up the relected laser ring off the floor.

Resulting image processed by the Propeller is :-

Yes we have 360° detect possibilities.

I am pleased with the result .... i have reduced the resolution by a factor of 5 for display purposes ....so plenty of spare (in my pocket).

URGENT :- Any ideas how i can adjust the size/angle of the laser ring (ie adjustable angle of laser mirror do-dadd) ?

UPDATE 8/11/11 :- adjustable mirror ..... made and ready for experimentation...See video....

        Tin Head pointed out that i could use a screw on the end of a servo, to push the mirror ....neat idea..... giving finer control.

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Use a GM9 or some kinda geared motor with an output shaft that is say, 3mm. Drill a hole through the center of the output shaft. Place a thin wire (coat hanger) through that hole. On the end of this wire, place some polymorph or something that will let the wire rub against the back of the mirror without "drilling" its way through. The wire stays stationary, the mirror and shaft spin. Obviously, you will need the mirror hinged and with a spring to return it upward. Attach a servo to the wire and you are good to go. Simpy push the wire down to increase the mirror angle. This is how airplanes with adjustable-pitch props do it.

4mm sketching....... during breakfast this morning.....

Second look ..... a second gear could be added off the drive gear......then this would be easier to use as the mirror driver...

Made first version, as seen in video above.....roughly follows my sketch only using secondary gear as active mirror angle pivot.

Ι was wondering how are you going to turn the whole thing with the motor....

If you're looking for a mechanical way to adjust the mirror while spinning, think of how the helicopter adjusts the angle of the rotating blades while spinning. Say you extend the motor axle a bit, then you mount an arm where the mirror is hinged at one end. Then have a washer on the axle and a spring between the washer and the arm. A servo can push on the washer compressing the spring. the end of the mirror can be attached to the washer by a rod so when the spring is uncompressed, the mirror has a small angle to the arm and when the servo presses on the washer and the spring is compressed, the mirror will be at a greater angle. I think it is quite doable.

Oh my, I've been away at the farm for the weekend and I see lots of comments and new ideas here...

Ok, here is how I thought of the system while I was driving 2 hours towards the farm on Saturday morning...

Take a bulk CD case (the ones that hold 25 CDs) and build the robot inside it. Then take another case, just the cover and install it on a pole mounted at the edge of the CD case so it is above the first case but with a gap of about 2 cm between them. Mount a stepper motor with an arm on the secodn CD case, motor upside down, the arm connected to it's axle and spinning. Mount 2 mirrors on that arm, one at 45 degrees, one at whatever angle is needed to have the laser beam follow the contour of the CD case right between the cases. Mount the laser below the motor, pointing upwards to the 45 degree angled mirror. Above the second CD case, mount the Wii cam pointing upwards, and above it, a chritmas globe (or bauble as you call it) that hangs from that pole in the back of the robot. Above the bauble you can mount a servo with a panning head just for looks. You can adjust the speed of the stepper as you need to have the camera find the spots faster. Pulsating the laser, as per your idea, will help things for sure.

Let me know what you think!

I can indeed picture the set up.... and i do like the idea of using two mirrors and stepper motor...... it leads me to think if i can add a micro servo to tilt the end mirror. hmmmmm as the sweep speed is realatively low....(it could be that only the end mirror is needed then)

This is leading me to think of making 2 separate parts linked with RF units ..... ie top half spins with servo-mirror + laser attachment with its own powersupply , bottom half contains wii-camera + bauble and sends serial RF signals to tilt mirror ,control motor speed  and extract data. (for this idea i would fix the motors spindel end to the robot and attach the electronics to the motor chassis which would rotate Hmmmmm)

Why Adjustable mirror ! :- If i can adjust the laser circle dynamically then it becomes more of a radar system....

Tnx for detailed explanation

I think I have an idea on this one .

The idea is to heat up the nitinol sprung in order to shrink and pull the mirror down .

When the heat is gone or reduced  the mirror will go in its original position or somewhere between depending the heat reduction.

With some tests I think that you will be able to control the angle of the mirror .

Rough sketch follows:


On the sketch when I say spring I mean sprung (wrong typing)

not moving the mirror? You can just change the angle of the laser with a servo and keep the mirror fixed :)