On Mon, Jan 17, 2011 at 10:08 AM, Oli Glaser wrote= : > That page is showing waveforms at a particular input voltage (of around > 12V I think) so you can't really go from that unless you are doing > exactly the same. At different input voltages/loads things will change. > > > * The plastic bag that the inductor came with says that it's a "power" > > inductor rated at 1/2 W with a resistance of 0.3 ohms. I then measured > the > > resistance with my multimeter and found it to be 0.7 ohms, but that cou= ld > be > > wrong? > > * At 0.3 ohms, (I^2)*R< 0.5 W, I would get around 1.29 A max. What are > the > > effects of pushing more than 1.29 A through this thing? > > * I don't plan on drawing more than 1 A, so the peak current through th= e > > inductor should be less than the waveform shown on page 26, and I shoul= d > be > > good to go? > > Not necessarily (I think quite likely not) > I can remember whether you are using this for buck/boost but I agree > with Alan that looking at some app notes would be a good idea. Also I > really recommend getting LTSpice if you have not already (great free > simulator in general) and using their example setups to simulate. > I just looked and they don't have the 3112 but they do have an example > of the 3533 which is quite similar (in /examples/jigs) - > I think a lot would be gained from running this example and changing > various parameters (input voltage, inductor series resistance etc) and > watching the pulse width, inductor current, output current etc. For > example what happens to the current when you have the in voltage lower > than the out voltage and vice versa? What happens to the pulse width > when in voltage is higher? What happens when you raise the inductor > series resistance? What happens when you change the load? > This plus going over the theory thoroughly should help I think (i.e. > don't just take the simulation results completely for granted - not > always correct/comparable to real world conditions - e.g. sometimes > totally wrong/misleading if set up the wrong way, although with the LT > examples they *should* be set up okay at least to start with) > > Also, doing similar in the "real world" will be good learning too (i.e. > just shove the inductor in and see what happens.. :-) ) Ok, I just ran the simulation. How do I get it to simulate more than 2 ms? This is what it looks like: http://img835.imageshack.us/img835/879/capturebx.png Seems that the current through the inductor is a lot higher than 2.7 A. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .