mikevein Posted July 27, 2006 Report Posted July 27, 2006 Hi allI've got problem witch building 0-30V 0.002-3A PSU (http://www.electronics-lab.com/projects/power/003/index.html). Voltage regulation works fine, but there is no current limiter, U2 (TL081)is heating and LED (D12) flashes all the time when power is on.Semiconductors are not damaged, I checked all diodes & transistors after soldering.I replaced two transistors: 2N3055 for KD503 [Tesla], and 2N2219 for BD139Please helpThanksmikevein, Poland Quote
audioguru Posted July 27, 2006 Report Posted July 27, 2006 Hi Mikevein,Welcome to our forum. ;DIf the negative 5.6V supply doesn't work then Q1 will turn on and cause U2 to get hot. Also the current regulator U3 won't work. Check that you have -5.6V across D7.Make sure that you have the substitute transistors wired correctly. If they have the collector and emitter mixed up then their current gain will be low and cause U2 to get hot.The current regulator works by reducing the output voltage by pulling the voltage down with D9. Make sure that D9 is not open. Quote
indulis Posted July 28, 2006 Report Posted July 28, 2006 Voltage regulation works fine, but there is no current limiter, U2 (TL081)is heating and LED (D12) flashes all the time when power is on.If he in fact has "voltage regulation", then Q1 can not be on, as it would pull U2's output low, and with U2's output low, there is no output voltage. Quote
mikevein Posted July 28, 2006 Author Report Posted July 28, 2006 yeah, now I checked it and now there isn't voltage regulation ;D Actually, it WAS before the LED start flashing - probably I short-circuited the Q3. I dont have the -5,6V, so I try to replace the elements in negative supply rail. Quote
SidRobo Posted May 30, 2017 Report Posted May 30, 2017 Hi i think this is the good place to ask my question. i made this one http://www.electronics-lab.com/project/0-30-vdc-stabilized-power-supply-with-current-control-0-002-3-a/#comment-173705 when i was testing my power supply, i found out that i couldn’t limit current. I test another motor and at that moment i saw that current is about 7 amps !!!!!When i disconnected the motor, voltage became 35V and i can’t change it with P1 Now neither P1 nor P2 work. but short circuit protection was working, but after doing few short circuit, LED didn't turned on pls help! Quote
audioguru Posted May 30, 2017 Report Posted May 30, 2017 The original project has many parts that are overloaded and they fail soon. We modified it to make it work better and to be more reliable. Quote
SidRobo Posted May 31, 2017 Report Posted May 31, 2017 14 hours ago, audioguru said: The original project has many parts that are overloaded and they fail soon. We modified it to make it work better and to be more reliable. Yes i saw that and i plan to design my pcb, but now i don't want my time and money that i put on orginal project, to be wasted. i don't expect to take 30V 3A from that, I would be happy even with 12V 2A at top. Can you help me with that sir? Quote
audioguru Posted May 31, 2017 Report Posted May 31, 2017 A 24V transformer has a voltage too high for the TL081 opamps. Use a transformer with a lower voltage like 15V. Replace the opamps that were strained. Replace the old fashioned 2N2219 with a modern BD139 transistor on a real heatsink. Replace the single 2N3055 output transistor that might be shorted. Re-calculate the values for the resistors that set the voltage and current. Quote
repairman2be Posted June 1, 2017 Report Posted June 1, 2017 (edited) Hello fellow Hobbyist, Take a look at this post: 0-30V Stabilized Power Supply Page 88 posted October 6, 2014 "http://electronics-lab.com/community/index.php?/topic/29563-0-30v-stabilized-power-supply/&page=88" I left out the TIP141, D10 and R15 as per his description. In fact I have had made those PCB Liquibyte designed and built my Power Supply with success. See here: "electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/&page=2" I have plenty of those PCB left. If you are interested I only ask AUD$2.50 per PCB plus posting cost in a padded envelope to your country. Cheers, William Edited June 1, 2017 by repairman2be corrected typo Quote
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