Outputting Voltages?

[Jaseca]

What is a good place to begin looking for developing functions that would either output voltages over serial, or some other hardware platform?

Base idea is to be able to control the speed of a small motor.

 

[lomn75]

look up Pulse-Wave Modulation, which is the voltage scheme you'll want to use. Analog voltages over serial is thorougly impractical, if not outright impossible.

Also, I would suggest you avoid any WinNT system for this application, as the hardware abstraction layer hates giving you good access. Ideally (if you're developing this for a business, say) I would suggest you have an intermediate microcontroller to handle the PWM plus an RS232 link back to a computer for monitoring and control; that will give you dedicated processor time on the output side.

 

[Jaseca]

Have any good sites or books I should look at. I originally was going to ask about a second device to control it like you were talking about, but had no idea how to even describe what I wanted to say.

edit: Also for an OS I planned on using either slackware or debian. Other people involved like freeBSD so that would be the other option.

 

[[MS]]

Another option is to ouput via parallel port to few registers tied to a DAC. I remember doing something like this back in a college lab.

Found the following link that may be of use. It has shows a simple R-2R DAC for conversion to analog and some simple code to output some values.
http://www.learn-c.com/experiment8.htm

 

[Jaseca]

update: sounds like the chem project we're doing this for will be using K'nex

 

[shieldforyoureyes]

I use an interface box from Prairie Digital. The only problem
is speed - it talks ASCII commands over a 9600 bps serial
line to the host - which makes it slow, but *incredibly*
easy to control. I bought mine to control some lights &
other gadgetry in an art installation at the Whitney Museum,
and I wrote the software, from scratch, in a couple of days.
Ran flawlessly 24/7 for three months.