Graphic LCD or 16 segment led displays, which will be easier to handle via BS ?

CuriousOne

Hello.

I have a task - need to display 2 line X 20 characters in certain language. This language is not supported by any of 1602 or similar devices, nor can be added to it, since 5x7 pixels won't be enough, at least 8x6 is needed. So, I have to use either graphic LCD, or 16 segment leds. Personally, I'd prefer 16 segment leds, due to their higher contrast and better viewing angles. But, LCD also is OK.

So, the question is, given the amount of chars to be displayed, which approach will be easier to implement in terms of basic stamp resources and additional components needed? (besides the price of LCD panel or LED segments itself?)

Mike Green

You're going to need some kind of display controller and LCD panels are more readily available than 16 segment LED panels with built-in controllers. You'll need something like 160 x 16 pixels at least. Here's one from Matrix Orbital that could work.

CuriousOne

Thanks.

Considering the prices of devices on the provided link, I'd better build controller by myself. I've checked, I'll need only 14 segments out from 16 segment display (but 14 segment display won't fit). I think, max 7219 or similars can be used, just I need to figure out, how to display arbitrary characters on it and also, whenever BS will be able to handle fast enough transfer of 14 bit per char, 50 types of chars, 20 chars per line ?

Mike Green

You've got a lot of complexity there. You'll need some serial shift registers, 2 x 8-bit for the segment drivers (74HC595), plus two decimal decoders for the digit drivers (74HC4514). You'll need a bunch of PNP and NPN transistors to do the actual segment / digit driving. Alternatively, you could use something like 3 x MAX6954 (at $9 each) to drive 8 digits of 14 segments each. The MAX6954 will automatically multiplex the displays and all you have to do is send the segment bits to a built-in RAM. In the first case, you'll have to do the multiplexing yourself and I suspect you won't be able to do it fast enough to avoid flickering with a BS2. It'll probably take 3-5ms for each digit at least and, for 20 digits, that's 60-100ms per scan.

CuriousOne

Yes, I also went by MAX6954 way, but it seems quite complicated to operate all that clock rise/fall syncro and so on. But I keep going with documentation, see how it turns out.