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  Robotic Madness
  Robotic base RSV2 prt 2

Generic robotic base with RSV2 Prt 2





These two photo's show the Parallax Professional development board and the Bluebell subsumption board along with the main wiring.

I had some spare time so have fabricated the main switch bank for the platform.

This is the underside of the switch bank from left which consists of a switch and green led for the electronics, far right switch and green led to the left for the motor controller and the black jack socket and red led for the charger.

Red led on and charging jack indicating the charging of the batteries

Top view showing the main wiring switch panel and fuses.

Another top view showing main wiring. The two main switches are rated at 5amps DPDT, 3 Chrome bezel leds 1 charging jack, 3 560ohm resisters for the leds 12v and 1 IN4001 diode inline on the negative side for the charging jack, this is to stop the 12v feed back from the batteries to the red led.

I have not decided yet as to the type of bump or IR sensors I will use, so today I reinstalled some of the electronics and wiring as shown in the above pics. The Parallax Professional development board here with the white board) has been mounted on a sheet of Perspex which has been mounted on the brass standoff's. The front board is the subsumption board from Bluebell design  here I will decide during the week as to the bump sensors, that is eight micro switches or five IR detectors around the base.

Proposed bump sensor: Sharp IR Modulator IS 471F These have a range of 2-3 inches depending on a resistor value
Type in [ IS 471F ] in the find box.


Description: GP2D12 Analog distance sensor
This sensor takes a continuous distance reading and reports the distance as an analog voltage with a distance range of 10 cm (~4") to 80 cm (~30"). The interface is 3-wire with power, ground and the output voltage and requires a JST 3-pin connector.


PART 10:



Just installed the front IR detector, This IR detector will be different from the other five as this came with the subsumption board. Two IR leds and Phillips IR receiver.

These are the parts used to house the detector, Three black Lego connectors and six short pegs. The IR leds fit perfectly into the centre hole and the connector fits perfectly between the two Perspex sheets, two holes are drilled in each sheet so that the Lego peg is a snug fit (We do not want a loose fit here) Slide the connector between the sheets of Perspex then fit the Lego pegs from top and bottom, once fitted this will give you a swivel point so that you can adjust the led angle.

Using another connector I have super glued the Phillips receiver to the central hole and bent the pins 90 degrees, Attached to this is a servo lead.

Finished assembly of IR leds and IR receiver. The other five GP2D12 Analog distance sensors will also fit in between the Perspex sheets at evenly spaced distances. I am waiting for these from the states as these are half the price than in New Zealand.

More to come on installing the GP2D12 Analog distance sensors When they arrive.


PART 11:


Micro switches and bolts.

Components for the micro bump sensors, micro switches, This is for the front, left and right sensors. Only 1 set shown. Lego plates, axles, collets photo's should describe what you need. You will need this times four for front, back and sides.

Insert short axles into part shown.

Place piece onto the triangler plate with collet.

Place triangler plate on top.

Insert longer axle into the tip of the triangler piece.

Now at the bottom where the small axle is holding the IR reciever remove the small axle and replace it with the longer one.

Place the whole assembly on top of the long axle, Making sure it can freely move from left to right. [This is important that it does]

Next step is to fabricate the alloy bumper, This is constructed out of 25mm x 1.5mm alloy strip, By hand bend the alloy so that it conforms to the perspex base shape and round off the ends with a file. Next remove the lego piece [ now this is an important next step]
very carefully add one drop of super glue to each short axle that joins the two triangular plates this will lock the whole assembly together. next place the Lego unit onto the alloy and make sure it is center, Drill a 4mm hole and countersink it from the front, We do this because we do not want anything to catch the screw head when the bot in moving. Once this has been bolted up slip it back on to the base and check that it is level, When satisfied remove again and super glue the Lego part that is touching the alloy, Once done replace back on the axle.

You should end up with something like this, The inside of the alloy should just be touching the micro switch levers which will push out the bumper and you should have no slop in the bumper.

This is the finished item, You now have to make another three for the back and sides making sure that you only have a small gap between the four alloy bumpers. The reason I have chosen to have micro switch bump sensors as well as the IR distance sensors is for security, If the IR detectors fail the bump will take over also the bump sensors are lower and will sense lower objects.

Micro switches now in place.

Bumpers in place.

PLEASE NOTE: I have made a modification the the underside of the bumpers, This includes eight small lego shock absorbers [Two on each alloy bumper] This was done to take the load of the micro switch levers, It also stiffens up the bumpers.

These are the lego Technic parts needed for the bumper cusion.

Assemble the parts as shown.

Next drill a hole in the perspex and place a lego axle peg in hole, This will be the anchor for the shock absorber cushion. Before you drill the hole that anchors the shock absorber make sure that you have compressed the shock absorber 1/3 of the way in before you drill the hole [ This is important] as when the bumper moves in and out both ends the absorber must be able to compress and expand.

Shock absorber in position, Drill a 3mm hole in the alloy bumper and fix the Technic part to the bumper.

Both shock absorbers now in place, Repeat this for all four sides. This produces a nice rigid but flexible bumper.

Underside showing the Lego shock absorbers.


PART 12:



My GP2D12 analogue distance sensors arrived today, So will be fitting these at the weekend.

These will be mounted on alloy brackets between the two perspex discs 45 degrees to the alloy bumpers.

Cut 4 alloy brackets to the shape above and mount them on the GD2P12 sensors.

The 4 sensors mounted around the top of the perspex base.

Close up of mounted sensor.


Wiring now connected to the sensors and held in place by plastic wire retainers self tapped to the perspex.


This is a close up of the sensor with a 47uf Tantilum capacitor connected across the + and - terminals to give a better stable reading from the sensor. This MOD was from Harry at Blue Bell Design, Thanks Harry.



copyright © 2007

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