Nice plan.DerKraken said:You're probably referring to the "chin" LED banks which make up the EQ bars. I've been thinking of changing that area in the name of simplicity anyways. Chances are those banks of 24 will be replaced by another 4 LED bank similar to the light bars above. I can scribe a grid pattern into the surface of some acrylic to make them look like individual lamps, which should cut down on current draw significantly.
You are correct again, I'm referring to the "worst" case, all LEDs on. Just remember, you can't pull unlimited current from batteries, but my knowledge only goes so far. Maybe you want to install one or two caps in front of the batteries, so there are no current spikes.
The ICs I was talking about can only support 62.5 mA per channel max, and your HEF4794B can only sink 40mA per channel (a channel would be connected to a LED bank), so they are out of question, I'll still post my prepared answer, might come in for future projects.
Instead of using single transistors, you can get transistor array chips, which combine 7 or 8 transistors in one chip, it's not only easier but often cheaper than single transistors. They go by the names ULN2803 and ULN2003, which are 8 and 7 pin NPN-transistorarrays, respectively. They can sink 0,5A / 500mA or 62.5 mA per channel max.
Now, the HEF 4794 ICs are basically shift registers and transistors in one component, but since it drains current instead of sinking it, you'll need to flip the LEDs (I think). You'll still need the resistors in front of the LEDs. If I read the data sheet right, each HEF4794B can sink 8 * 40mA = 320mA.
Anyway, loving the helmet, great work, and also good electronic knowledge there, brilliant project.
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