Sign in to follow this  
mikevein

0-30V PSU - prblem with current limiter

Recommended Posts

Hi all

I'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 BD139

Please help

Thanks
mikevein, Poland

Share this post


Link to post
Share on other sites

Hi Mikevein,
Welcome to our forum. ;D
If 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.

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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!

Share this post


Link to post
Share on other sites
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?

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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 by repairman2be
corrected typo

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this