Is my design (Propeller LED) correct?

[Hesam Kamalan]

Hi,

I've designed propeller LED, for showing Clock, but I don't know is it correct or not.

In this project we have 32 LED for showing clock.
4 Latch for keeping data.
ULN2803 as a buffer
PIC 16F877A and DS1307 RTC


guid me please.

 

[3v0]

I see no reason to use the ULN2803A. The pic can easily drive the inputs to the 4 latches.

 

[duffy]

I don't see the reason for using the term "propeller". There's no Propeller chip in there, and the led's are apparently used for a clock - ?

Like 3V0 said, the ULN2803A is unnecessary. You could also save yourself some wiring pains and free up port pins by cascading shift registers instead of using those parallel latches.

 

[3v0]

I think "propeller clock" is another name for a POV clock.

The latches will be faster then shift registers but either way would be good enough. The shift registers might be less expensive.

 

[duffy]

Oh, yeah - for persistence of vision you probably wouldn't want the shift registers.

 

[Ubergeek63]

Oh, yeah - for persistence of vision you probably wouldn't want the shift registers.

shift registers are fine in you run them fast enough. If there is still a flicker you just add a transistor to turn off the LEDs while you are shifting.

Dan

 

[duffy]

...or easier still, just use the parallel output latch.

I was thinking the time delay to load the shift registers was going to be an issue with POV, but on second thought maybe not.

 

[Hesam Kamalan]

Thank you,

Ok. I'll reject ULN2803A. But, what motor is suitable for my project?
I've searched and I've found that HDD motor is used for rotating the board
(YouTube - the most amazing RGB propeller clock ever seen)

Since the board will rotate, I think, VCC and GND must connect to my board through motor. Witch type of motors you suggest?
I think the weight of board is less than 600g.
I think turqe of 3000RPM is good.
Also I think motor should work with 12v.

 

[3v0]

They are using a fan to turn it.
600 g sounds heavy.

 

[Hesam Kamalan]

I think it is heavy for fan but motor (hard drive) can handle it.
Also I think weight is not more than 300g (I told 600g with heat sink and other components witch may be becom necessary).

 

[kchriste]

You could use a LDO regulator and pre-regulate it's input voltage down to 7 Volts or so. Then you may not even need a heatsink.
You almost have enough IO pins to do away with the latches all together. If you used a PIC with more IO, you could save some weight that way.
One question however. How are you going to set the date and time on your clock?

 

[Hesam Kamalan]

You could use a LDO regulator and pre-regulate it's input voltage down to 7 Volts or so. Then you may not even need a heatsink.
You almost have enough IO pins to do away with the latches all together. If you used a PIC with more IO, you could save some weight that way.
One question however. How are you going to set the date and time on your clock?

It's not difficult, I have to show three things. Hour-hand, Minute-hand and Second-hand.
In each instant I'll show one of them and I think if I show these three things 30 times in a second, and rotate of 20 turn permin Second (1800rpm), it will work properly. like these:
YouTube - The Propeller Clock - Final Version
YouTube - Virtual Clock Demo 1
YouTube - The Propeller Clock

 

[Hesam Kamalan]

OK,

I bought all components but I don't know what type of DC motor you suggest for rotating the board?
I think, VCC and GND must come from motor. Is it true or not?