Hmm... There might be better ways to go about this. Since you mentioned All Electronics I poked through thier offerings quickly. Look at this one http://www.allelectronics.com/cgi-bin/item/PS-511/480/222_WATT_SWITCHING_POWER_SUPPLY_.html It's a PC supply, but it's only $10 and it puts out 32A of 5.1V power. Seems like a solution to me. -Denny On 2/14/06, Peter Todd wrote: > > Alright, no laughing, this is a serious linear power supply, not some > wimpy half-amp unit. Not that I'm claiming my design is any good... > > I've got a device I built that has 64 stepper motors with associated pic > chip drivers in it. These are extremely cheap steppers, > > http://www.allelectronics.com/cgi-bin/item/SMT-57/400600/STEPPER_MOTOR_.html > to be exact. Total current draw averages about 22A-25A but can peak as > high as about 40A. Not that I am totally sure about those numbers, > that's just assuming that the amp meter on my testing power supply > works. The motors are not synchronized to each other. To be exact, they > play Conways Game of Life... > > The the problem is as follows. I built a linear power supply using a 28A > 6.3V transformer from digikey. 237-1255-ND. 4x LM396K 10A regulators in > parallel through load-sharing resistors regulate the voltage. For my > first attempt I used a standard 50A 600V diode bridge, MP506W-BPMS-ND > That didn't work, the final voltage at the "5V" line ended up being > about 3.5V, causing the master PIC controller to crash. > > My second bright idea (ha!) was to try to reduce the voltage drop by > using those fancy schottky diodes I noticed in the catelogs... So I > ordered three 115CNQ015ASL-ND 15V 110A and made them into a diode > bridge. (they are two diode packages) That worked beautifully, giving me > a usable 4.2V line, until after about 30 minutes of running I heard a > loud bang. The main AC fuse had blown, though not the 40A DC fuse, and > the after some testing the diodes were found to have developed internal > shorts. All three seem to have done this at once! > > So, any ideas where I was going wrong? One possible culprit I think is > how I soldered them, I made up a circuit board and used a heatgun to > heat the whole packages up and "reflow" the heat-spreader tabs to the > PCB. All this done without much regard to temperature other than go > slowly and use as little heat as need be. > > In any case, I just want to get some ideas before I go off and > potentially spent another $40 on diodes, or try to find a bigger > transformer. > > -- > pete@petertodd.ca http://www.petertodd.ca > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist