Pressure Gauge of LED's

I'm building a pressure gauge that will be made of a circle of 50 led's. I will have a transducer on one of the analog pins and will use that data to tell which led's to turn on. Pretty simple. The question is this... Would it be easier to...

  • Use the Duemilanove I already have and charlieplex/multiplex, and/or use an led driver. I have only read on the forum here and wikipedia about charlieplexing and multiplexing; have no experience with.

  • Buy an Arduino Mega in which I would have plenty of digital pins to control the led's w/out a "middle man".

  • Some other option that I haven't even thought of.

Thanks.

Couple of questions...

  • Could it keep multiple lights on at once? As pressure climbs, I want the led's that have already been turned on to stay on.

  • "sends out some quantity of ONEs" - would that be done digitally or with an analog pin? Sorry, I have no experience with shift registers.

Here's a CAD drawing of what I'm doing... C:\Users\JD\Desktop\gauge panel.jpg

The pic was a jpeg but the link points to

http://c/Users/JD/Desktop/gauge%20panel.jpg

Probably not going to work :)

Ha, yeah. Not at my work computer anymore. Noticed it didn't work, but was in a hurry. How would I post it properly? Thanks for the help. I'm sure I can find a tutorial somewhere on shift registers to figure out the code. Sounds like the route I want to go. Thanks again.

Thanks. I'll post the finished product.

One more question...

I will actually have (3) gauges total on my panel. Could my Duemilanove handle all (3) of the gauges, that consist of 50 led's each? I was reading and thought I saw some other types of shift registers that run off a seperate power supply. Thanks.

I will actually have (3) gauges total on my panel. Could my Duemilanove handle all (3) of the gauges, that consist of 50 led's each? I was reading and thought I saw some other types of shift registers that run off a seperate power supply. Thanks.

The arduino is made to power itself and a maybe a few low power gizmos. Depending on the power requirements of your LEDs, you may need an external power supply for them.

but it will switch externally powered devices no problem

Kind of what I figured. Thanks for the help.

Ran into another problem. I've decided I'm actually going to have 4 of these gauges on a panel; 1 duemilanove per 2 gauges. However, that means I have to externally power 28 shift registers and 200 led's. The led's alone will amount to a 4 amp pull if they were all on. I'm having trouble finding a power supply that's capable. Any suggestions?

I noticed on the Deumilanove description that the recommended input voltage is 7 - 12 volts. Just to make sure I'm understanding correctly, this is referring to using the onboard regulator via the power jack or Vin, right? If I got power from an external 5v regulated power supply and plugged into the 5v pin, that would work, right? In short, how would I power the Arduino with the 5 volt power supply Mr. Crowley suggested? Sorry to be such a newb, just don't want to fry my board.

It is o.k to power an Arduino by providing the 5 volts directly into the 5volts hole…

However it is some kind of waste to power 100 LEDs @ 2A…
The brightness will increase the more LEDs shine. This could be intended. Normally one tries to dim the LEDs so that the illumination stays somewhat constant, be it 10 or 100 are shining (there has to be some compromise with <3 LEDs…)

This can easily be done by software PWM to the shift registers; this can be extremely simplified by an additional transistor at the common anode side of the LEDs.

This would reduce the needed amperes down to 200mA !!

When using an external power supply you should also think of a 3.3Volts supply. This is enough for green and red LEDs and reduces the needed power (not the amperes!) by another 3.3/5.

It is no problem to supply all the shift registers from the Arduino as long as they are open collector types (or “low side drivers” as they are sometimes called).

Also don’t be afraid to drive 3.3 volt logic by Arduino pins; a serial resistor of 10k will suffice for protection.