I need an accurate 50Hz AC voltage source.
That can vary from 0 - 5V.
So i was just wondering weather i could do this.
In the diagram attached, i wil be using a micro-controller which will give input to my DAC.
And i will give an AC signal to my Vref of the DAC.
So i will be getting an AC signal at my analog output controlled by the output of the micro-controller.
Will this setup work??
if yes, what are the design constraints?
current is not at all a problem for me , because I am going to give this voltage to a high impedance circuit . is there any problem in having a voltage follower circuit in the output if there is any loading effects. My doubt is that will this circuit be able to produce the ac waveform exactly 50hz ac that I am giving to it.
Yes, you can produce an accurate 50Hz sinewave in this way, you should follow the D2A with a buffer and a low pass filter. I would also suggest altering the size of the signal using a digital potentiometer (or something similar) - if you do it before the D2A quality will suffer as you reduce the output level.
hi akg
current is not at all a problem for me , because I am going to give this voltage to a high impedance circuit . is there any problem in having a voltage follower circuit in the output if there is any loading effects. My doubt is that will this circuit be able to produce the ac waveform exactly 50hz ac that I am giving to it.
Thanks for your interest
He could probably apply a biased sine wave to a unipolar DAC and AC couple the final output, but clipping could be a problem unless he leaves some headroom, which would seem to complicate the design.
He could probably apply a biased sine wave to a unipolar DAC and AC couple the final output, but clipping could be a problem unless he leaves some headroom, which would seem to complicate the design.
My understanding is that he wants a digitally controlled attenuator for a 50Hz signal. If this is true, then "give an AC signal to my Vref of the DAC" makes sense to me.
Dont cascade your D/A that way. Just choose a converter that has the appropriate resolution that has already been suggested.
Consider the possibility of not using a D/A at all thus avoiding code & controllers. If you need constant adjustment the D/A may be the right way to go but if you are going to set your 50Hz and make one adjustment to it (DC or otherwise) there could be simpler ways that do not require a D/A with all that "overhead"
Can you tell us what you need it for? You'll get better responses.
Also there seems to be some confusion about the nature of your signal.
signals are loosly talked about as being AC if it is a function of time irregardless of DC offset that may be present.
[Vsin (wt) + C] = AC signal
[Vsin (wt) ] = AC signal
[C] = DC signal. Not a function of time.
We are planning to make an auto calibrator for our power quality card, which we are designing. It’s an ASIC based design. Going for a test bench will take a lot of time and money and if we design this it can be used as a software controlled test kit that can simulate a lot of test conditions.
The energy card is based on ade7758. Its input is .5 peak to peak in both current and voltage channels.(see the fig attached - in real condition we have to use CTs and voltage divider ). So we decided to make a 5-volt accurate source and to scale down it using a voltage divider network to produce .5v peak to peak.
. The minimum step we want is.0025 in 5 volts to meet the calibration requirement of the meter and so we decided to go for some DAC with ac signal in its Vref so that we can change it accurately. Since we don’t need any change in frequency we are giving ac 50 Hz through a step down transformer.
We are looking for a 12 to 14 bit , bipolar, low cost DAC and that are easily available in the markets do u know any? .we got some data sheets like MAX 5544 MAX5141-44,. but none of them are available in local markets(Bangalore, India). so i thought about cascading two 8 bit DACs .it will be helpful if you could suggest one fits for the requirements
We are looking for a 12 to 14 bit , bipolar, low cost DAC and that are easily available in the markets do u know any? .we got some data sheets like MAX 5544 MAX5141-44,. but none of them are available in local markets(Bangalore, India).
I don't think improving the resolution is the right term.
BUT you can increase the resolution. The advantage is that the voltage steps are much smaller. If the steps are small enough, you could probably be able to produce a true sinewave output from the binary bits.
Just increase the number of bits in the DAC to increase resolution.