I assume you would also have to do some slightly tricky bit-twiddling in the sketch, because the pattern for each single digit would have to be spread over the max's 8 data registers?
4543 can be used with both common anode AND common catode (just change Ph)
Looks great!Also attach a resistor between base and emitter on all 2N3906, 10 kOhm will be OK.But using 74LS....?What century are you from.Good luckPelleEdit.IF you power everything from 5volts, you do not need the NPN transistors, just connect R12-R15 directly to the arduino.You also have to invert the code for this outputs.
Hi red913,...1. Easiest first: use a 5V (or less) supply so you don't need a regulator. If using batteries, use 3 or 4 rechargeable AA or AAA cells instead of a 9V battery. Nothing in your circuit needs 9V, and that regulator will just waste four ninths of the 9V battery's charge. a single battery just seemed easier to manage vs a large AA holder... but 3 AA isn't so bad. Perhaps I will go that route. Less parts is always better.2. Connect the switches to ground and use the Arduino's internal pull-up resistors, saving 4 resistors.This will still work even if I'm only using Arduino code right. I know the chip in the Arduino has them onchip but I couldn't find it being on chip for the Tiny.3. Your tiny84 and 74hc595 are two 14/16 pin chips. There is a single 28 pin chip that could replace them: a mega328. The '595 has a maximum current source/sink of only 70mA, whereas the '328 can handle 200mA for a much brighter display. You won't need a crystal for the 328 because it will run at 8MHz just fine without. You can buy a blank 328 without a bootloader and program it using your Arduino exactly as you planned to do with the tiny84.Ya, that's a good idea. It would definitely make the code a lot easier as multiplexing has proven more difficult than my rudimentary coding skills can handle. Although I've found some stuff online and with help from my brother I have almost finished the code. Maybe I'll just save the register for another project. AlsoI'll still need to source current from VCC, via a transistor, as a single digit pulls over 60mA and in total the display should exceed 240mA.4. Pelleput is right about using only the pnp and not needing the npn. Alternatively use only the npn and then you don't even need any base resistor. See earlier discussion about emitter-followers between me and the other Paul.Oh, I thought I needed a PNP to do high-side switching. Also I'm not sure I'm clear on the emitter-follower thing. This is what I put together from what I gathered on wikipedia.So if this schematic is right I could ditch the pnp's in favor of just a single NPN. That would be nice. 5. As the 74hc595 is limited to 70mA, you could replace it with a tpic6c595 which has the same pinout but can sink up to 100mA per output (but not source at all - not a problem with your common anode display).When checking with my DMM my current is just under 10mA each pin, which is pretty much the Shift Register's limit;as you pointed out; once I add in the remaining 6 pins that is. So using a Mega instead is sounding more appealing. Thanks for the suggestions...
Also I'm not sure I'm clear on the emitter-follower thing. This is what I put together from what I gathered on wikipedia.[/color]
a single digit pulls over 60mA and in total the display should exceed 240mA.
Ah! So I'm the MAX7219 expert now, eh?
I clearly cannot speak for your display.
while you are at it - no penalty, just another "segment".I will criticise your pushbuttons. They should all return to ground, with the "value" resistors going from them to the analog pin and a pull-up from it to 5V. A 1k resistor in series with S1 will allow you to determine multiple simultaneous button presses rather than S1 always taking priority.
Schematic for mega328 solution.