hello, maybe you know this guide from gideon-tech: http://www.gideontech.com/content/articles/205/3 i want to build it but with 20 instead of 10 leds. though not stretched to use 20 leds but have 10 leds and mirror them so that the middle is lit up when hdd utilization is low going to the edges with higher utilization. something like this Code: [.........OO.........] <- low utilization [........OOOO........] <- higher utilization [....OOOOOOOOOOOO....] <- even higher utilization my thought was building 2 circuits which get the signal from the same source (e.g. only one opto-coupler) as the lm3914's max sink current appears to be 13 mAs. are there any simpler/better solutions? any help appreciated
If the LEDs are in series, and the supply voltage a few volts more than the sum of the forward voltages, no problem. It's the method used on macroman's 20-LED Knight Rider. The 5V supply used in the Gideontech circuit probably won't be enough for 2 x 2V leds, but that's just my guess. But no problem going to 12V, maybe double-up the two pd resistors (330R and 470R) to 680R and 1k. And I think Marsupial has the 220uF cap wrong way round on the circuit diagram, 'white box' is positive side.
as long as they LM3914 can provide enough amps on its output it will be possible to connect up 2 led's in parralel to one of the outputs. I am assuming that the outputs are 5V. if it can't provide you with enough power then your suggestion of using 2 LM3914's connected to the opto-couple will also work if i'm not mistaken. I could be wrong though, its been 6 years since i completed my electronics degree and i haven't used any of that knowledge since.
thanks for your answers. DR_D, as far as i can tell, the lm3914 acts as a sink, not as a source. i'll look through the datasheet again and see if 2 leds instead of one would work.
just FYI i've built the circuit with 20 LEDs, i simply put each second LED in series with the original and it works (at least with red LEDs)
Have a look at Cylon Eyes bargraph and look at the .003 MOV file. Excuse the loud noise from the systems ... I'll have a small kit available shortly for this. I can provide either just the programmed microcontroller, or a complete built board - you provide the LEDs. Dean.