jrhodes

alright it happened again i fried my driver chip right away now this is after i ran the supply with just a led as a load. i hooked up my ampmeter and and showed from voltages 0 to 30v, 0 to 93 millamps my current limiter was funtioning correctlly cause i was able to set my current at 20 millamps and my voltage would come up i cant remember but i think it was about 6 some volts and then it would go no higher unless i adjusted current limiter. the light was working properly. everything was great until i hooked up my motor. it was only on ten sec or so i preset my voltage to 18v cause its a 18v motor. then i turned my current down to almost nothing. then hooked in the motor. nothing. so i turned up the current regulator and after so far the motor kicked in and almost immediattly bd139 started to smoke. the ampmeter read only 83 milliamps. but it almost seemed to me like it fried right away and was just running on 30v which is where my mains are at. im not sure it all happened so fast. i built this supply to operate this motor. i actually built 2 side by side one to run the pic chip and circutry. and one to power the motor that the pic controlls with pwm. i kept frying the motor controller chip L6203 when ever i stop the pic cycling which some times you cant stop the moter during testing so it may be running one direction then you stop the pic its outputs go 0v which 0v is a full speed reverse signal to the l6203 throwing the motor in full reverse next thing i know the l6203 is fried. so i wanted some current limiting thus this circuit. i believe this power supply should work for my prototype its just why does it fry bd139 thers no current flowing here except for maybe through r16. in all fairness i should say i didnt put heat transfer compound under my chip to heatsink i planned to but i was only running it for a few seconds.

right again it was the bd139 now i get my variable back and i checked my amps with just a led and i can control my amps thanks guys for all your help will try to get pics when done

i turned the driver transisters around and the powersupply worked great right up until i hooked up my 18v dewalt drill test motor i may have over amped the circuit i dont know i didnt have ampmeter tied in but now i get 34 volts through the output nothing less on picmasters verion theres a seperate board for the driver transister and output transisters. ive disconected them and still get 34v0lts at pin 6. in audiogurus version c9,c6,r12,r11are all that are connected to pin 6 i dont see how any of these could have failed and output 34volts to pin 6 i have switched chips same thing also i do get 0 t0 11 volts at inveting pin 3 just noninverting pin 2 stays at 0 volts also i do get 0 t0 11 volts at[glow=red,2,300] noninveting [/glow]pin 3 just [glow=red,2,300]inverting pin [/glow]2 stays at 0 volts sorry had these backwards Posts merged by moderator. Please use the modify button (it looks like this ) in future rather than making multiple posts.

audioguru you are unbelievable you know i had the bd139 on the board and changed them out with a tip3055 cause i could only get the bd139 into126 package thinking the plastic case would needa larger heatsink i have tip3055s as output transisters but these are much larger than the tip3055 i got at radioshack and replaced the bd139s with well iguess i switch them back cause you are correct the pins are backwards hope i dont fry them with all this soldering and desoldering. cant believe i missed this. audioguru your incredible thanks for getting me straight ill let you know how it works

yes of course my picmaster version U1 is your march 11 rev2 U2. the one emmiting to the driver base emitter which im using tip3055 to-220 also i using the mc34071 chips which none of them are really even getting warm. im using 2 56k resisters at the output terminal to add a 112k load. question: the negative feedback coming through r12 and c6 (your version) this signal is stable is it not or does it drop and raise as i adjust p1(your version) on my board the output of u2 goes as high as 34v but only drops as low as 16volts and these voltages seem high driving tip3055 isnt the base emitter voltage of tip3055 only 7 volts. my output never drops below 16v my inverting and noniverting pins 2-3 follow each other up from 0v to 7v then only the inverting pin 2 continues to rise to 11.15 volts. why isnt the noninverting pin 3 continuing to rise due to its connection to p1 instead my negitive feedback cirtcuit through r12 and 6c voltage rises to 11.15volts is this due to the 3x gain. which brings me back to why doesnt my voltage drop below 16volts with the pot all the way down. i check my pinouts thought they looked good cant see them being a problem do you still think i have one switched around ill send pickmaster pdf its pretty thurow i used his eagle design printed it with laser and irond it and eched it the traces wernt perfect they all look good now EL_power_supply.pdf

hey guys ive posted here a couple times this time i think i got it right. need help on my progect ive built the newest version of the supply and for the most part it works. my problem is the output of u1 ( this is the picmaster version so follow his print) ive got 34v at the rails but my output at u1 doesnt drop below 17 volts and it goes up to 34 volts i thought this was a lower voltage output not maxed at 34v to drive the transisters. also i noticed when looking at the scope as im increasing or decreasing p2 that pin 2 and pin 3 will follow each other from ov up to about 5 to 6 volts then pin 3 will rise on its own (as i increase pot) and output will then start to rise from 16v to 34v switched chips so i know its good. hey guys i know you love this stuff please help ive got a couple months on this progect and would like to see it work. also this is all with 2 series 56k resister conn at output.

can anyone help me i ve built a dual power supply. i did picmasters version and im having trouble ive got my 11.2 volts out of u1 so i know my reference voltage is right. my current limiter was working before but i found a bad trace to ground and my voltage out of u2 was always 17 volts now when i fixed the bad trace i can adjust up to 17 volts only and current limiter light dont come on. i get a max voltage of 34 volts between ground and positive rails i get a max at pin6 of u2 of 34 volts but only get 17 at output havent tryed second power supply cause im waiting ing .33ohm resisters does a heatsink on transisters have to be grounded

hey guys i built a duel supply the lastest vesion of the picmaster anyhow i had some bad traces and got that straight . i have 34 volts at main power rail to ground but i only get 17 volts max at my output ive got 11 volt out of u1 so thats working also before fixing the bad traces my led was coming on and off with current limiter pot now it doesnt come on at all. i havent tryed the second board yet waiting on .33 ohm resister also using 5watt .47 resister at tb2 or (r7)