Post by thread:[OT] Re: DAC Conversions..

Hi Scott, I've got an old national data book so I'm not sure the PDF is the same. Just a guess from what you've said, and not knowing how you have it hooked up, is it possible you don't have a negative voltage at pin 3. I doubt this chip will work with a single power supply. Are you using an OPAmp or resistor to convert the current output into a voltage? Or is it possible the chip is "pins up", do you have another to try? Regards, Heinz At 3:31 AM 2/3/99, Scott Shidel... wrote: >yeah, I have the PDF, and have it hooked up like they do...still cant get >it to work,,,Rheir diagrams arent really complete though,..they dont hjave >a complete in cicuit diagram.. <snip> >> >> At 10:27 AM 2/2/99, Scott Shidel... wrote: >> >Can someone point me to a site with some projects for the national >> >dac0800? I am using one in a project and get get it to give me anything >> >but 1-1.4v out..its running with a 5v vref... >> > <snip> ------------------------------------------------------------------------

On Wed, 3 Feb 1999, Heinz Czychun wrote: > Hi Scott, > > I've got an old national data book so I'm not sure the PDF is the same . > > Just a guess from what you've said, and not knowing how you have it > hooked up, is it possible you don't have a negative voltage at pin 3. I > doubt this chip will work with a single power supply. > Hmmmmm:) Yah. For power I have +5v and 0v..For a 5v vref, what would you recommend my voltages be? > Are you using an OPAmp or resistor to convert the current output > into a voltage? > Resistor for now. Only load on the DAC other than the resistor is my DMM..When I put it into service I am going to use an op amp. > Or is it possible the chip is "pins up", do you have another to try? > Yeah, I suspected that...chip number 2 is the same way..didnt go for 3:) I think you have a good point with the power suply voltage..what would you recommend? {Quote hidden}> Regards, > Heinz > > At 3:31 AM 2/3/99, Scott Shidel... wrote: > >yeah, I have the PDF, and have it hooked up like they do...still cant get > >it to work,,,Rheir diagrams arent really complete though,..they dont hjave > >a complete in cicuit diagram.. > <snip> > >> > >> At 10:27 AM 2/2/99, Scott Shidel... wrote: > >> >Can someone point me to a site with some projects for the national > >> >dac0800? I am using one in a project and get get it to give me anything > >> >but 1-1.4v out..its running with a 5v vref... > >> > > <snip> > ------------------------------------------------------------------------ > ----------------------------------------------------------------------- The Pinto Page: http://www.eng.usf.edu/~shidel Join the Ford Turbo Mailing List! http://www.FindMail.com/list/turbo/ Scott -71 Pinto, stock 2.3 turbo, 13.67@98, radials 8.1@85 1/8th mile on slicks -85 Merkur 13.764@98 on radials&3300lbs! Under $300 in mods! ------------------------------------------------------------------------

At 5:54 PM 2/3/99, Scott Shidel... wrote: >On Wed, 3 Feb 1999, Heinz Czychun wrote: > >> Hi Scott, >> >> I've got an old national data book so I'm not sure the PDF is >>the same. >> >> Just a guess from what you've said, and not knowing how you have it >> hooked up, is it possible you don't have a negative voltage at pin 3. I >> doubt this chip will work with a single power supply. >> >Hmmmmm:) >Yah. For power I have +5v and 0v..For a 5v vref, what would you recommend >my voltages be? That depends on what voltages are available in the final design. As a staring point I would suggest a balanced supply starting at some voltage higher than logic voltage. For TTL logic the specs. suggest a 10V reference, with a 5k resistor to provide an IFS of 2ma. If you then gnd -Io (pin 2) and connect the inverting input of an opamp to Io (pin 4), the voltage at the output of the opamp will go from 0 to IFS (2ma) * Rl (Rl being the feedback resistor between the opamp output to the inverting input). That relationship will hold true, of course, only while the opamp is in the linear region. If you just use a resistor at Io you will get a desending voltage starting at the supply voltage. {Quote hidden}> >> Are you using an OPAmp or resistor to convert the current output >> into a voltage? >> > >Resistor for now. Only load on the DAC other than the resistor is my >DMM..When I put it into service I am going to use an op amp. > >> Or is it possible the chip is "pins up", do you have another to try? >> >Yeah, I suspected that...chip number 2 is the same way..didnt go for 3:) >I think you have a good point with the power suply voltage..what would you >recommend? > >> Regards, >> Heinz >> >> At 3:31 AM 2/3/99, Scott Shidel... wrote: >> >yeah, I have the PDF, and have it hooked up like they do...still cant get >> >it to work,,,Rheir diagrams arent really complete though,..they dont hjave >> >a complete in cicuit diagram.. >> <snip> >> >> >> >> At 10:27 AM 2/2/99, Scott Shidel... wrote: >> >> >Can someone point me to a site with some projects for the national >> >> >dac0800? I am using one in a project and get get it to give me anything >> >> >but 1-1.4v out..its running with a 5v vref... >> >> > >> <snip> >> ------------------------------------------------------------------------ >> > >----------------------------------------------------------------------- > The Pinto Page: http://www.eng.usf.edu/~shidel > Join the Ford Turbo Mailing List! > http://www.FindMail.com/list/turbo/ >Scott >-71 Pinto, stock 2.3 turbo, 13.67@98, radials > 8.1@85 1/8th mile on slicks >-85 Merkur 13.764@98 on radials&3300lbs! Under $300 in mods! >------------------------------------------------------------------------