Jup. That's why I decide to do a constant light version. The light level is very nice, and the circuit can be run on voltages between 2.1 and 6 volts with no danger to the leds. Speed is the same, leds appear brighter. KreAture ----- Original Message ----- From: "Jinx" To: Sent: Monday, August 20, 2001 5:19 AM Subject: Re: [PICLIST] [EE]: LED Matrix : there's got to be a cheaper way? > > This will be so fast that the leds won't even visibly light up > > before data has passed them. I have tested this with a > > 32x8 array and 4 pinwheels rotating on the display. Updates > > then took 1.28 us and the led's were lidt for almost 125 ms > > giving 8 fps. (For this I used the image stored in ram, and > > just fed the display a new block every 125'th ms. (To test > > 25 MHz shift frequency) > > Looked kinda cool :) > > Sounds kinda cool too !! > > Your point about the refresh rate is what I was a alluding to > about timing headroom. Give the micro everything to do > and the LED off/on ration will suffer, causing flicker. One > point about drivng LEDs with pulses though - most have > best output efficiency at a particular current. Too little and > they won't be their brightest, too much and you're wasting > power or unnecessarily stressing components. Some fore- > thought is needed to get the best out of the whole display. > Even the choice of switching transistors will affect the light > level, for example high-current Zetex ZTX types will switch > pulses far better than the ubiquitous BC548 and yet they > are smaller and not much more expensive (ZTX are my > choice for IR transmission too, vastly superior) > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads