Recently we had a bit of fun building a simple artbot out of a dc motor, bulldog clip, tea canister and textas - There are plenty of Instructables on this topic to take inspiration from.
We made several metres of rainbow coloured wrapping paper and started thinking about improvements we could make.
We came up with the idea of a rainbow painting unicorn robot. The concept evolved into this project.
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Step 1: Design Process
We thought we’d modify one of the girls plastic toy horse figurines, add batteries, a simple dc vibratory motor, a horn, some wings, a pearlescent white and rainbow paint job and plenty of glitter.
It soon became apparent that the centre of gravity of the horse would be too high and it would just topple over and not be very graceful.
We decided we needed a figurine with a broader base and a lower centre of gravity for our unicorn robot. So we audited our toys and made a shortlist. Eventually we chose the rhinoceros because we wouldn’t need to add a horn.
Step 2: Tools and Materials
- Drill with assorted bits
- Soldering iron
- Wire cutters
- Rhinoceros figurine
- DC motor
- Copper tape
- Paper clips
- Alligator clip
- Male to female jumper lead
- 5mm LED
- 51 Ohm resistor
- 2 x AAA batteries
- Blu tack and super glue for running and permanent repairs
Step 3: Preparing the Rhinoceros
We wanted to centre the motor in the rhinoceros figurine. So we decided to drill a vertical hole through the thoracolumbar area.
The problem was the diameter of the motor was 22-23mm and we didn’t have a dill bit that size.
We drilled a few holes and then used files to get the final shape. This took a while.
We then drilled 2 horizontal holes 11mm in diameter to hold the AAA batteries.
We also drilled a hole in the hindquarter of the rhinoceros so we could mount an LED too.
We checked the batteries and motor fitted into the holes.
We then used the copper tape to make positive and ground rails along the sides of the rhinoceros. Some tape was added to its neck to assist with connecting the batteries in series. Another small section of tape was added to the shoulder on the positive side so we could make a switch to turn it on and off.
Step 4: Making the Connections
To connect the batteries in series and to connect them to the positive and ground rails we used paper clips we had bent into shape.
We found that bending the end of the paper clips into little coils provided a better connection with the batteries than just straight bits of paper clip wire.
Battery 1 negative was connected to the ground rail by a paper clip. The clip was soldered onto the ground rail. We later found that heating and then cooling the copper tape during the soldering seemed to have an adverse effect on the adhesive.
Paper clips were used to connect battery 1 positive to battery 2 negative via the copper tape on the under side of the neck and to connect battery 2 positive to the copper tape on the shoulder.
We wanted to put an “on / off” switch on the rhinoceros but didn’t have much space left. We decided to cut a male-female jumper wire. The exposed wire on the male wire was solder to the copper tape on the shoulder and the exposed wire on the female wire was soldered to the positive rail.
The positive wire from the motor was connected to the positive rail and the negative wire was connected to ground.
The LED was also connected to the rails with the resistor between cathode and ground. By my calculations I think we needed a 51 Ohm resistor- We couldn’t find one in our box of parts so we used the next closest a 63 Ohm resistor.
We connected the circuit, the LED lit up and the shaft on the motor spun. The alligator clip was then put on the shaft to create the vibratory motor.
Step 5: Rhinobot Rampage
We tested the rhinobot out on a hard flat suface. It went on a clockwise spinning rampage for a minute or so before the vibrations rattled and moved the poorly adhering copper tape subsequently making the battery connections come loose from the circuit.
With a little bit of blu-tack to re-establish the connections we got the rhinobot up and running again. These connections were pretty dodgy and the motor speed was quite variable. We exploited the dodgy connections and changed the placement and pitch of the alligator clip to get the rhinobot to move differently. We were even able to get it to reverse in a straight line.
Extra glue was added to the copper tape and the connections were fixed.
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