I'm building a POV clock but one of the requirements is to be able to send a message to the clock to display while its spinning (around 10 characters).

We are planning to use a PIC microprocessor with c programming etc. The PCB hasnt been built yet but wondering what kind of device I could use to connect to the POV clock so I can achieve this? We'll be using about 10 LED's.

Thanks

 

Maybe a phototransistor on the spinning board and an IR led on the stationary side.

 

Maybe a phototransistor on the spinning board and an IR led on the stationary side.

When I did a display like this I used a hollow axle for the spinning portion. I aimed the LED into one end of the axle and put the phototransistor looking into the other end.

Other hints:
You may want an index pulse to let you measure the speed and position of the spinning LED's.
You want to keep the spinning part as light as possible to make it easier to balance it.
You can use slip rings to get DC power to the spinning portion. That way you will not have to spin batteries.

 

You can make a rotating transformer from two ferrite pot cores.
Use a nice high frequency around 20-40 khz, then you can frequency modulate the transformer drive to convey information- then you have 'wireless' power and data to the rotating mechanism.

 

If you go the route of 2 slip rings to provide power you can also put an AC signal in the same two lines for communication.

If I was doing this that is the way I'd go.

 

If you are doing the slip-ring thing- this company has very nice cartridge type solutions:

http://www.mercotac.com/

Lasted about a year in my 60 RPM clock.

 

If you go the route of 2 slip rings to provide power you can also put an AC signal in the same two lines for communication.

If I was doing this that is the way I'd go.

This is worth a try but I would worry about contact noise corrupting the signal. Having multiple parallel contacts would help. I don't know if commercial slip rings have this problem or not.

 

Mercury wetted slip rings are nice and quiet.

 

I've decided to go with the IR and a few resistors etc and plug that into my PIC micro controller. I was thinking of using an app to send the message from my phone (using the built in IR) to the IR on the POV clock. It this feasible? Any suggestions on how to make the app? Ie code types. I'm a novice and have never written an app before!

I'm using a TSOP 38238 IR receiver. Will this do?

 

I haven't developed an app, but have worked with my friend to develop one for me. Depends on the phone. Most phone manufacturers have a development kit which is used in writing an app. The kit will include documentation and a library of routines to use for the phone. iPhone users need an Intel Mac to develop and publish apps. Some people have used a virtual box on Windows to run OS X, but Apple frowns on the practice. If you'd like to develop apps for the App Store, you could be banned.
Developing for Android appears to be less restrictive. This link is a review of several app development kits.

 

Not sure what your clock looks like but - why not spin everything?

Make your PIC circuit very small. Then you only need to feed the power in. This could be slip-rings or two halves of a ferrite pot-core.

Presumably you need to have some kind of sensor so that it knows where "12 o-clock" is. Fixed magnet, hall-effect sensor on your spinning PCB.

In fact (I'm making this up as I write), larger fixed magnet, open coil + diode on the PCB -induce enough current in the coil to power it as it goes round.

Think I saw someone who had made something like this to fix to one of the spokes on a bicycle wheel - displayed messages as they rode.

 

If I go with Bluetooth, can someone recommend an actual device I can use? It has to be through hole as the PCB is through hole. And not arduino!!!