How can I write an analog voltage on arduino?

Question

My question reference's a problem I'm having with my eletronic solution. I'm using a CI LM3915N-1 to build a bargraph circuit, where I need to turn on a few LED's depending the voltage that my CI receives. The problem is the arduino just write PWM and not analog voltage. So how can I solve this? how can I convert the PWM to a analog voltage?

Here is a image of the Bargraph circuit: enter image description here

To understand better what I want, is to imagine that at Signal Source will be an arduino sending AC signal.

See related: http://electronics.stackexchange.com/questions/12345/converting-pwm-into-an-analog-signal — embedded.kyle, Nov 12 '13 at 14:02
Why are you converting a digital signal to an analogue signal and then back to a digital signal (lit LEDs)? Wouldn't it be simpler, and more accurate, to use a digital solution? Shift register? — RedGrittyBrick, Nov 12 '13 at 14:11
Thanks embedded.kyle and RedGrittyBrick, btw RedGrittyBrick, Im trying this solution because Arduino UNO only have 12 digital pins, and all my digital pins are used so far, so I need to use an analog pin ;x — Guilherme Garcia da Rosa, Nov 12 '13 at 14:56

score 3 · Answer 1 · answered Nov 12 '13 at 14:06

There are 3 options:

Put a low-pass filter on the PWM pin so that only the very low frequencies in the signal generated by the PWM, which will be at approximately the equivalent analog voltage, are allowed through.
Connect a separate DAC to the Arduino, either serial or parallel, in either integrated or discrete resistor ladder form.
Use an Arduino that has a DAC built-in, such as the Arduino Due.

score 0 · Answer 2 · answered Nov 12 '13 at 18:40

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If you are ok with limiting LED number to 8, you may have much simpler solution utilizing serial in parallel out register. 74HC595 will do the trick without any need for digital-analog-led conversion. You may chain shift registers to make longer led strips, that will certainly require additional ICs for each 8 bit group. As a bonus you will have individual control of every LED.

There are 12-bit registers also, although they may be harder to source. I'm not sure, maybe there are even longer one's somewhere.

answered Nov 12 '13 at 18:40

x4mer

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HEF4894B is a nice 12-bit LED driver, chainable and with PWN brightness control if you'd wish to use it. – x4mer Nov 12 '13 at 18:45
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The TLC5940/5941 are 16-channel, high-voltage PWM drivers. – Ignacio Vazquez-Abrams Nov 12 '13 at 19:35

How can I write an analog voltage on arduino?

2 Answers2