#robotics Logs

Jan 10 2012

08:58 rue_house .
09:02 theBear hey buddy... ok... so you like pid's and stuff... say i got a circuit similar to http://electronicdesign.com/files/29/1929/figure_01.gif ... maybe in opamps... say i'm making a little thing to keep a resistive heated something at X temp... i put a 10k-ish temp sensor in the pwm width/vcc divider there.. is that any less usefull than having a 3rd comparator for set-point (pot) vs thermal-sensor -> feeding u1b in that first schematic ? i figure by
09:02 theBear the time i have a little less than infinite gain (p-i-d adjust style) on the set-point vs thermal sensor, that it'll be just as easy, if not easier to 'tune' with just 2 stages (wave gen and comparator/pwm) vs a 3rd stage for a "set temperature" "comparator" (has to be an opamp with less than infinite gain, otherwise the whole concept of pwm is useless)
09:04 theBear side-question, if i'm doing a temp-sensor/maintain heating-element temp to heat liquid in a vessel, it makes most sense to put the temp sensor on the element vs the liquid, in order to avoid stupid-time-delay-oscillation and generally will get a more steady resulting temp ?
09:06 rue_house http://eds.dyndns.org/~ircjunk/circuits/measind/pwm_stikr.gif
09:07 rue_house J1 is input, J3 is pwm outputs
09:07 rue_house R5/6/7 are scaling
09:10 rue_house hmm
09:10 rue_house I cant think now, is the only conclusion
09:22 theBear err, yeah, that's just, well i coulda drawn that <grin> i'm talking pure analog, basically temp sensor in the control section... but don't worry if yer tired... i'm pretty sure i'm right, and if it doesn't work, i'll just add a stage