pov poi

Hello. I am designing a pov poi to swing around and make patterns. easy huh.

my plan is to use an array of 50 rgb common anode led on each side of pcb.

To drive led I'm using tlc5940 in series. (10 of) I'll use 0.1uf capacitor across 5v to gnd for decoupling at each chip.

The processor Ive choose to use is atmega256. mainly for memory for storing images.

The images will be stored on ram as a long array.

I will have this embedded with isp headers for programing.

I will program through ftdi breakout board.

I will communicate to the tlc chip through arduino library and send all the first 150 bytes. for the first 50 led. ( I will have to multiply the rgb code by 4 as its a 12 bit pwm which will slow down but not by much I would believe. ) Then tlcUpdate() to send data to chips. I will then delay x then repeat with the next 150 bytes.

How long will this take and will this be fast enough for a good pov picture? Speed is my main concern. I've noticed everyone uses teensy for this as it has more ram and faster spi. Will this atmega256 spi be fast enough for a reliable picture? or should I bite the bullet and get a teensy? I'd just prefer to do an embedded system. nice and tidy .

My other option is apa102 but I'd again prefer to fabricate the whole thing.

My other concern is power usage.

If I have 100 rgb led at .6ma that 60A, at 50% brightness it's 30A if the lights on a third of the time it's still 10A

I was going to use a ubec for powering the led but I might have to shrink the array.

any comments suggestions or warnings?

I guess I can install a 10a ubec, but I will have to boost the batteey pack. I was going to use maybe 6 nimh batteries with a charge circuit for in circuit charging although I still haven't honed in on my exact approach here.

anyway back to the first point. will my spi be fast enough?

my other concern is power usage. if I have 100 rgb led at .6ma that 60A

I'm not sure what a "ma" is, but if you mean 0.6 mA (600 uA), your arithmetic is way out.

Please fix your shift key. It appears to be faulty.

POV, SPI, mA etc have meaning, lower case means nothing.

If you want help, make an attempt to make your post readable by using capitals in the places they are normally required. This includes starting sentences. This makes it easier for us to read and make sense of what you are saying.


Sorry writting on my phone and is quite a annoying as it autocorrects everything.

I'm glad my arithmetic is way off with power usage as that's a serious battery required. Yes I did mean mA.

I can see my calculation error now, I converted 60mA to .6A.

Any ideas if the SPI on my atmega chip will be fast enough?

Sorry about the sloppy post have had the flue for a couple of days.

Tangles84: Sorry about the sloppy post have had the flue for a couple of days.

Really? :grinning:

Dam auto correct.

Tangles84: Sorry writting on my phone and is quite a annoying as it autocorrects everything.

Everybody loves to use this excuse; I'm not sure why - perhaps because it is an easy out for blame.

How about this: Turn it off. Every phone that has auto-correct, has the ability to shut it off.

It's better to have poor spelling (and improve it over time - not to mention capitalization), than it is to have perfect spelling (albeit at the cost of potentially the wrong words appearing). If someone else (ie, a grammar/spelling nazi) points out a misspelled word, take it in stride, learn the proper spelling, and move on with the new knowledge.

Over time your posts will become clearer to others, potentially more concise, and you won't be as reliant on a poorly performing crutch.

It didn't correct "writting"

Someone would've though I was on a grammar forum?

whether or not you believe it was autocrrect isn't my concern. I am very comfortable with my level of vocabulary and my writing skills.

I was hoping for some help or constructive criticism on my project.

Has anyone got any useful comments rather than critiquing my spelling and grammar?

Six amps is still quite a lot of wire weight to be swinging around.

Someone would've though I was on a grammar forum?

Grammar and spelling (and arithmetic) are all very important aspects of programming, so in that respect, you're absolutely correct.

I did not mean to come across as being picky on your use of English. It is simply that everything in lower case makes it hard to read.

We have many that have English as a second language. Everyone reads past the spelling and grammar as it is obvious that they are not native English speakers.

My apologies for being off topic.


AWOL: It didn't correct "writting"

Maybe it makes allowances for lawyers.