dac explained

[R.thayer]

Can anyone explain to me how a digital to analog convert works? I would like to get a 1 to 10 volt signal from a computers parallel port or serial port or any other port. I need this signal to be variable as it is going to control spindle speeds.

[ViperTX]

Well....firstly you look at the number of bits.....the digital side....8 bit....you have 256 bits +-1 lsb.....which is generally the accuracy.....so you can have about 255 increments....a 10 bit would give you 1024 discrete increments.

You then need to take the output of the DAC and feed it into an Operational Amp (OpAmp) to give you the voltage swing that you want....basically a big buffer for the output of the DAC.

You send bits.....say the decimal number 128 (which you convert to binary as 1000 0000) and that should give you 1/2 the voltage you need....

There are some tutorials on the web somewhere.....

[R.thayer]

I think I understand how they work. So let me explain how I see it. Ok I will hook a dac up to the output of a parallel port. If I use a 8 bit dac then I send a decimal number to the dac using software. If the input voltage of the dac is lets say is 10 volts and I send the 100 to the parallel port then I would get 3.92 volts out of the dac. Is this how things work with these dac?

[HillBilly]

Some of the printer port CNC control software let you PWM one output pin for spindle control. This gives you 0-5v dependeing on duty cycle ( On time. ). This can be sent to a op amp to adjust the swing to 10 volts. Some of the new VFD will accept this 5 volt PWM input.

Darek

[R.thayer]

So I am using emc2 to control my lathe. My lathe is spectra light turning center that has been retrofit with new controllers and motors. It now uses a parallel port. I would like to know how I can control the spindle using emc2 and the pc. The spindle has a variable speed motor control on it now that uses a positive 10 volt signal to vary the speed. The spindle does not reverse so it only needs 10 volts positive. How can I do this it also has a encoder on the spindle that I would like to interface with the software as well. I would like to be able to thread with this machine. Hope to hear from you very soon and thank you