Clock With Heat Reactive Paints

Hi,

I'm trying to design a clock with hands that change colour at a certain angle. To do that I want to use a heat reactive paint which changes colour when heated around 40 deg (C). I've attached a diagram of the possibilities that apply to the colour change.

My question is what's the best way to design the clock so that it automatically changes the colour of the hands? I've started thinking about the components, but not sure if I'm in the right direction.

- Nichrome strip to heat up the hands of the clock
- Motion sensors embedded in the body of the clock to detect the location of the hands.

I'm fairly new to electronics, so simple instructions will be very appreciated.


Thanks for your help in advance.


Maryam

**broken link removed**

You will need some type of slip ring contacts to get power for the heaters on the hands.

You could perhaps determine position by a sensor (hall effect perhaps) to detect a small magnet attached to the clock mechanism gears.

Another way would be to embed IR emitters and sensors in the clock face to detect the reflection when a hand goes by.

Motion sensors on the hands would require several more connections that would have to go through slip ring contacts.

crutschow said:

You will need some type of slip ring contacts to get power for the heaters on the hands.

You could perhaps determine position by a sensor (hall effect perhaps) to detect a small magnet attached to the clock mechanism gears.

Another way would be to embed IR emitters and sensors in the clock face to detect the reflection when a hand goes by.

Motion sensors on the hands would require several more connections that would have to go through slip ring contacts.

Click to expand...

Using the slip ring idea, perhaps another wafer with an encoded track pattern for the colours

Thanks for your guidance Carl and Eric.

I think the slip ring would work best if I was to make the clock gear system. I'm however using a simple one with screw bezel (runs with a single AA battery) and I was going to attach the heaters to the hands.

Now if I'm to use the hall sensors or the IR emittor/sensor, could you guide me on the schematics? (i.e. I think I need two sensors to detect both hands and somehow program it to heat the hands when they're both turned "ON"?!

Thanks again. I highly appreciate your direction.

~maryam

maryam7 said:

Thanks for your guidance Carl and Eric.

I think the slip ring would work best if I was to make the clock gear system. I'm however using a simple one with screw bezel (runs with a single AA battery) and I was going to attach the heaters to the hands.

Now if I'm to use the hall sensors or the IR emittor/sensor, could you guide me on the schematics? (i.e. I think I need two sensors to detect both hands and somehow program it to heat the hands when they're both turned "ON"?!

Thanks again. I highly appreciate your direction.

~maryam

Click to expand...

hi,
If the drive mechanism can stand the extra load, you could switch the colour periods using a dedicated set of slip rings, no electronic sensors.