I plan to use a simple 2 flip flop design to make chasing LED:
**broken link removed**
Which should result in:
**broken link removed**
And there will be around 60 at the time. The V supply is 5v and I'm trying to figure out the way to drive about 15 LED per output. Since the flip flop circuit isn't designed to handle that many LED, and I don't want to build 8 sets of flipflops too much space wasted.
LEDs are max 2.5v 30mA and I plan to limit to 2v 20mA to keep them from blinding people and being distracting.
There are 3 possible ways. One is using H bridge like this:
**broken link removed**
(forgot to add resistors to transistor base)
4 transistors control half of all the LEDs, one set of 15 lights up and other is off and since both are connected to just 1 flip flop it will always be alternating. A second set of H bridge controls the remaining LEDs. On paper it looks good.
But I'd need transistors that are capable of around 3A each minimum. Advantage: since transistor has typical 1.4v drop each or 2.8 total so I'd only need to drop .2v or so but finding resistor that is high watt enough is going to be tricky. Would zenier diode in reverse bias at Vcc work to lose that 0.2v? Or is there something else? Or I could just leave LED at 2.2v and pray it won't be too bright anyway.
There's also using MOSFET instead of transistor but I have no experience with them. So I don't know what are the typical V drop from source to drain or what are required to use them. If you think MOSFET is better, please advise.
3rd option is to use 4 transistor or MOSFETs, each one controls set of LEDs. Fewer transistors total:
**broken link removed**
I'd have to drop quite a bit, about 1.6v so 2 regular diodes in series from Vcc? Or I could use 16 LEDs in 2 parallel x 8 series configuration? About 1.7v each LED this way so defiantly won't be bright but still usable.
Any advices would be appreciated.
**broken link removed**
Which should result in:
**broken link removed**
And there will be around 60 at the time. The V supply is 5v and I'm trying to figure out the way to drive about 15 LED per output. Since the flip flop circuit isn't designed to handle that many LED, and I don't want to build 8 sets of flipflops too much space wasted.
LEDs are max 2.5v 30mA and I plan to limit to 2v 20mA to keep them from blinding people and being distracting.
There are 3 possible ways. One is using H bridge like this:
**broken link removed**
(forgot to add resistors to transistor base)
4 transistors control half of all the LEDs, one set of 15 lights up and other is off and since both are connected to just 1 flip flop it will always be alternating. A second set of H bridge controls the remaining LEDs. On paper it looks good.
But I'd need transistors that are capable of around 3A each minimum. Advantage: since transistor has typical 1.4v drop each or 2.8 total so I'd only need to drop .2v or so but finding resistor that is high watt enough is going to be tricky. Would zenier diode in reverse bias at Vcc work to lose that 0.2v? Or is there something else? Or I could just leave LED at 2.2v and pray it won't be too bright anyway.
There's also using MOSFET instead of transistor but I have no experience with them. So I don't know what are the typical V drop from source to drain or what are required to use them. If you think MOSFET is better, please advise.
3rd option is to use 4 transistor or MOSFETs, each one controls set of LEDs. Fewer transistors total:
**broken link removed**
I'd have to drop quite a bit, about 1.6v so 2 regular diodes in series from Vcc? Or I could use 16 LEDs in 2 parallel x 8 series configuration? About 1.7v each LED this way so defiantly won't be bright but still usable.
Any advices would be appreciated.
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