tag:blogger.com,1999:blog-27601886.post2063716572792126782..comments2023-11-24T03:58:57.577-05:00Comments on Iestyn Lewis: Computer Dashboard, part 4 - D/A Conversion 2Iestyn Lewishttp://www.blogger.com/profile/14601475856729755453noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-27601886.post-76401164458321686112008-04-15T10:53:00.000-04:002008-04-15T10:53:00.000-04:00You sort of make sense. David Byrne urges you to ...You sort of make sense. David Byrne urges you to stop. The description is somewhat simplified, due to space considerations, and to the fact that my understanding has grown fuzzy since doing this project. The resistors are all indeed either R or 2R, I think in my case they are 100K and 200K resistors. <BR/><BR/>Each of the junctions functions as a voltage divider. Current always wants to find the easiest path from source to ground. In the diagram, there are 2 ways for the current from each input to get to ground - either by going through the Load at upper left or directly to Ground at upper right.<BR/><BR/>So in the case of the MSB, on the left, there's a whole world of pain in the form of resistors in between that junction and the ground on the right. Much easier just to go through the load (the meter), and thereby change the reading on the meter by a lot. <BR/><BR/>In the case of the LSB on the right, the current sees a whole lot of pain to the left, and would much rather just go to ground. But a little tiny bit makes it through to the meter, and changes it by a little. <BR/><BR/>In between, you get varying percentages of current divided between ground and the meter. <BR/><BR/>All can be determined by Ohm's law, V = I*R. But the tricky part is always deciding which one of those remains constant, so you can figure out the other 2.Iestyn Lewishttps://www.blogger.com/profile/14601475856729755453noreply@blogger.comtag:blogger.com,1999:blog-27601886.post-6239812890988724652008-04-14T23:06:00.000-04:002008-04-14T23:06:00.000-04:00Are all your resistors the same, uh, resistance, o...Are all your resistors the same, uh, resistance, or do they vary? I'd assume that they need to vary so as to ensure that each input is reduced the correct amount, but they're all labeled R and 2R, so does the number of resistors the signal passes through automagically arrive at the correctly proportioned voltage? Does R/2R indicate that the initial voltage is reduced by twice as much as the resistance between steps and that how much it is reduced depends only on the amount of signal the meter is expecting? Do I make any sense?Keathhttps://www.blogger.com/profile/11841071812126390601noreply@blogger.com