The Medical Scanner (11122005 2155)

After spending the last few hours completing the Playmates Star Trek: The Next Generation Tricorder, my mid was still going on high gear. So, I needed something to wind it down. That was when I came across the toy fan I originally bought for Kristine but have yet to give it to her as I was afraid that it might injure her even thought he fan’s blades were made of soft plastic. It is strange why would anyone want to light up the area to be fanned. Not only that, both the motor and the bulb are a huge drain on the batteries.

This is the toy fan I got for RM5.90. Slide the red switch and the soft transparent blade turns and the bulb also

lights up. And nest of all, it does not makemuch noise. Unfortunately, its not going to be a fan anymore

The Concept

In most Sci-Fi films, a prop is “working” if it has flashing lights or moving parts the actors can interact with. And most of the time, there are no sound coming form the props. It was added in post-production. Anyway, when I looked at the toy fan, many ideas were coming through my mind. The shape was quite interesting because it was “ready” for any project without much modifications. It already has a slot for the original slide switch if you wish to use it back. As the fan uses 2x AA batteries, the cavity inside has been conveniently moulded for them.

So, it was decided that the toy fan was to become a scanner of some kind. In Star Trek, a scanner would have lights flashing in sequence, very much like a Next Generation Tricorder.

The Circuit

Under normal circumstances, it is not unusual to use two main ICs; the 4017 Decade counter for light up the LEDs in sequence and the 555 time to generate the speed of the circuit. However, I decided not to use them but rather, rely on one of MicroChip’s PIC. This is because the cylinder housing the electric motor is very small. The 555 and the 4017 ICs alone would have taken up most of the space and moreover, these two ICs require more than 3Volts to run effectively. By using the PIC chip to replace them, I have effectively reduced the component count. The replacement of the PIC chip has its advantages, mainly:

So, now the LED sequence is, instead of lighting up from one by one (one LED only from bottom to top), it will fully light up to form a bank of 10 LEDs before moving two from bottom to top, two LEDs together.

I used the breadboard to prototype the circuit. It has a piezo buzzer to make some simple beeping sounds as well. The

circuit draws power from the 2x AA batteries at the back

The Process

Once I have the LED sequence that I am satisfied, I begin to gut the toy. And start to replace it with my own circuit. Because I still need to wire the LEDs in a tight space, I used very thin wires, the same ones used for wire-wrapping prototyping boards, which you do not need to do any soldering.

The fan has been opened and I get to keep both the motor and the bulb

Testing the circuit before sealing in the cyclinder. The thin green wires are called wire-wrapping wires. I added in the flashing red LED in the very last minute

This is how the scanner looked like when finished.

The fan originally consists of a few parts: The battery connector, the switch, the motor, the bulb, and its transparent blue casing.

By the time I finished, I was too tired spray paint the scanner and redecorate it. In my tired state or mind, I’ve forgotten to cut a rectangular hole for the LED module at the top.