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I'm looking for a DAC board to use with an Arduino. I need something with an 8-bit digital input through SPI that outputs a 0 Volt to 5 Volt analog signal. I'm hoping for something in the $10 to $15 range.
A DAC is just a resistor and a capacitor, with a variable PWM signal from the mcu as the input.
Having some DDS in mind?
But the PWM the microcontroller puts out is a 500 Hertz signal that may generate an audible buzz.
QuoteBut the PWM the microcontroller puts out is a 500 Hertz signal that may generate an audible buzz.AVRs can do a much higher PWM frequency. Just keep upping it until it gets quiet.
No, nothing like that. I'm using an Arduino microcontroller to generate the throttle signal for a motor controller for a golf-cart type motor. You helped me on this project a few months ago, Soeren. As Admin says, I could just use a filter on a PWM signal. But the PWM the microcontroller puts out is a 500 Hertz signal that may generate an audible buzz. I could filter the signal, and I could increase the PWM frequency, [...]
That's different from a pulse-width modulation approach (with a low-pass filter) that, as I understood it, Admin said most DACs use.
I guess he just meant "when you make a simple one yourself", as there are several approaches to a D/A-C, but most are based on R-2R ladders.
Remember that a D/A-C needs a buffer (and that would probably be the case for your Digital Resistor as well).The buffer needs to have a low output impedance of max. 1/10th of the controllers input pin impedance and it needs to have a high impedance input to not load the D/A-C (or "Digistor").
The MCP4901/4911/4921 devices are rail-to-rail voltage output DAC devices designed to operate with aVDD range of 2.7V to 5.5V. Its output amplifier is robust enough to drive small signal loads directly. Therefore, itdoes not require an external output buffer for most applications.
Apparently, the MCP4901 chip has a resistor string architecture that includes an output buffer. The datasheet says:QuoteThe MCP4901/4911/4921 devices are rail-to-rail voltage output DAC devices designed to operate with aVDD range of 2.7V to 5.5V. Its output amplifier is robust enough to drive small signal loads directly. Therefore, itdoes not require an external output buffer for most applications.Do you think I'm safe without a buffer? The problem is that I know very little about the controller input. It's a black box that the controller maker will not provide any details on.
BTW. what in the datasheet makes you think that it's made like a digital potentiometer?