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0-30V Stabilized Power Supply


redwire
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Guest liquibyte

What I'm saying is that at zero adjustment on P1, RV1 will only adjust to -185mV and -170mV.  Won't go less than that won't go to more than that.  P1 at 100% only gives 10V tops.  I have two of these, isolated, and they are both doing exactly the same thing.  Something is definitely not right.

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1) Which opamp part number is your U2?
2) What is the value of RV1?
3) Do you have an R10 connected to the slider of RV1?

Measure the voltage at the output of U1. It should be 11.2V. The voltage pot feeds 0V to 11.2V to the input of the output amplifier (it has U2 in it) that has a voltage gain of 2.68 times. Then when the voltage pot is at maximum the output of the project will be 11.2V x 2.68= 30.0V.

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Guest liquibyte

liquidbyte,   what is  the voltage at pin 6 on U1 and what is the voltage of pin 3 and pin 6 on U2 when you are at max voltage?


Pin 6 on U1 is 4V and 3.6V to gnd.  U2 pin 3 is 2.79V and 3.1V and pin 6 is 6.7V and 7.2V to gnd.


1) Which opamp part number is your U2?
2) What is the value of RV1?
3) Do you have an R10 connected to the slider of RV1?

Measure the voltage at the output of U1. It should be 11.2V. The voltage pot feeds 0V to 11.2V to the input of the output amplifier (it has U2 in it) that has a voltage gain of 2.68 times. Then when the voltage pot is at maximum the output of the project will be 11.2V x 2.68= 30.0V.



U1, 2, and 3 are all TLE2141's.  Rv1 is 5K both sides.  R10 is connected to the slider on both sides.

Output of U1 pin 6 is 4V and 3.6V to gnd as I said above.  I'm getting from 0 to 100% on RV1 a difference of only 9mV.  I may have to re-buy the parts and have a board made and start over because something is very wrong with these numbers.
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U1, 2, and 3 are all TLE2141's.

Good.

Rv1 is 5K both sides.

Good.

R10 is connected to the slider on both sides.

R10 should be 1k ohms with the TLE2141 opamp.

Output of U1 pin 6 is 4V and 3.6V to gnd as I said above.

The 11.2V reference circuit using u1 is very simple. Its supply can be anywhere from 14v to 44V. Measure it.
Make sure its zener diode is 5.6V at 5mA because a 100mA zener diode voltage will be low like yours is.

post-1706-14279144635461_thumb.gif

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Guest liquibyte

Liquidbyte,  can you post the values of all of the pins for U1

They should be close to:
Pin 2  5.6v
pin 3  5.6v
pin4  0V
Pin 6  11.2V
Pin 7 41 V

Also check the resistance value of R5 and R6  to see if they are both 10K.

Sorry folks, the wife and I have been sick for a few days and I just didn't have the energy to keep working on this at the time.

OK, here are the results from both channels U1 voltages.

Left side:
2 = 1.48
3 = 4.03
4 = 0
6 = 3.24
7 = 3.3

Right side:
2 = 1.32
3 = 4.86
4 = 0
6 = 3.92
7 = 4.28

R5 and R6 are both 10K.  R10 is 1K on both sides.  U1 supply is 38V on right side and 37.5V on left side.  U1's zener is 5.6V from Digikey (http://www.digikey.com/product-search/en?x=6&y=14&lang=en&site=us&KeyWords=BZX79C5V6-ND).

The odd thing is that nothing is even getting warm to any significant degree even though both power supplies are only outputting around 10 volts.  Current limiting is working as well if I adjust the current pots.  I'm starting to wonder if I didn't accidentally solder a short on both sides that's causing this voltage drop to ground.
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Liquidbyte,

On U1, Pin 7 is the supply voltage from the bridge rectifier, it should be around 41V.  You state that the U1 Supply is around 38V on the right side and 37.5 on the left.  I don't know how that is possible.  You list the voltages for every pin but 1 and 8. Those pins are not utilized.  Did you accidently connect pin 1 or 8 to the high side instead of pin 7.  It appears you have a error on your schematic and both boards are incorrect.

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Guest liquibyte

I've got U1 going through the 10V zener along with U3 to drop the voltages a bit because my rectified output was over the 44V limit.  I've also run U2 through 2 diodes to create another seperate voltage drop.  Excuse the reordering of the part numbers on the board image, it's also come back to bite me in the butt.  I think it's wired correctly but I'm starting to wish I had waited for the money for an etched board instead.  I may eventually do that with a new set of parts that populate the board.

Attached is an eagle board layout I did to help me while soldering this up.  I'm also attaching pictures of the actual job itself.

post-107142-1427914463553_thumb.png

post-107142-14279144636119_thumb.jpg

post-107142-14279144636654_thumb.jpg

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Liquibyte,
The parts designation numbers on your parts layout are all mixed up:
1) U1 on the original and on my modified schematic has it as the 11.2V reference but your U1 is the current regulator.
2) U2 on the original and on my modified schematic is the voltage regulator but your U2 is something else.

Whose schematic are you using?

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Guest liquibyte

My U1 = U3, my U2 = U1, and my U3 = U2.  I renumbered the parts in the layout to follow current conventions regarding parts being numbered left to right and top to bottom on the schematic side of things.  I think I'm just going to redo this as the parts to redo the board will only run about $30 or so including the op amps.

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Liqidbyte

Trace back from the bridge rectifier to pin 7 with your voltmeter to find where your voltage is dropping off.  You have a lot of solder on that board. Perhaps you have a short somewhere.

If you are getting 10 V output it seems U2 (on the original project) is functioning properly.  With an output of 3.92V on Pin 6 of U1 feeding U2, that has a gain of approx 2.6 equals approximatly 10 volts.  You problem may be minor.

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Guest liquibyte

Give me a bit on that and I'll let you know how it goes.  I'm attaching the schematic I did in Eagle that I worked from to show the parts numbering that I redid.

post-107142-14279144637789_thumb.png

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I'm attaching the schematic I did in Eagle that I worked from to show the parts numbering that I redid.

1) Your parts re-numbering causes a nightmare to troubleshoot it.
2) Some of your text overlaps other text.
3) Many of the external connections are confusing.
4) The schematic is too small or is too large.
Then maybe I will not look at your problems anymore.
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Guest liquibyte

My parts numbering is according to what I've read is the industry standard for readability.  Some of the text overlaps because I wanted to stop rearranging things and start building.

The external connections are paired up on the 2N3055's because they are connected at the back of the case.  For instance, the .33 ohm resistors on the emitters are connected at the back and joined after the resistor and run to the board using one wire.  The base connections and the collector connections are done the same way but just joined from one transistor to the other.

I don't understand your fourth comment.  Suit yourself if you want to help or not as I'm sure the reason for the failure of the design is my fault and not yours but being rude about it doesn't excuse the fact that the original schematic sucked and needed re-doing and I did it around my needs of having a large case and two supplies.  I attached my work to show you all what I had done, not to piss anyone off.  I had planned on re-doing the schematic once again with proper numbering and none of the external connections and attach the eagle files in order to help out the next guy in line that wanted to build this.

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Guest liquibyte

My fourth comment is about the clarity of your schematic. The large one is much too large for my pc screen and clearly shows only a small part of it. The small one is a perfect size but its fuzzy faint lines and text are difficult to see. My schematic is also shown here.

In the interest of being useful and helping others, instead of trying to troubleshoot my power supplies, I spent the last several hours updating the schematic and arranging it in Eagle.

In the zip file are the schematic and a parts list and I'm attaching a png file that's made from the schematic and edited to be black everything on a white background.

There is no board file because you can't mount the 2N3055's, the pots or the bridge rectifier on the board.  In that vein, folks will have to replace those parts in Eagle with their respective terminal blocks, pads, or other associated parts that will be routed off board and then route the board themselves.

The zeners aren't what you will want either because they aren't the right packages because the defaults in Eagle suck in that regard.  The TLE2141 is a modified part that I made myself out of the TLC080P which has basically the same pinout.

post-107142-14279144639139_thumb.png

30V.zip

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Guest Zinci

Hi all, First post.  8)

I have read this (and the original thread with lost attachments) for few days now, and I can say that this is most entertaining thread that I've encountered on this Forum. The other one is as good as this one. Very nice.

All we need is another diagram, electrically same as the original "good one", with completely different part numbers. Why would that be helpful, it escapes me. Maybe so I can make another folder with the same diagram?

So far this is what I understand we have for this project:

1. Original diagram. We all know that is "bad for you" :)
2. "Modified" diagram, which does not have PCB endorsed by the "big boys", with missing part numbers on diagram but present on part list. Parts on the part list nowhere to be found on the diagram (I believe that has been fixed now). Well, at least a mismatch, as they would say in my "electronics course"  ::) down the road.
3. Redwire's 5A "version". Well, a little reading and we know there is little difference between the 3A and 5A(emphasis on difference). Repeated here for about 4 times at least.  He posted the Eagle double sided .brd (no .sch file that I could see.)
4. Picmaster's new (PCB) "design" and new part numbers. Electrically same really, but still different, for added bonus confusion it depicts different output transistors. It is quite nice of him to give the PDF file of the board and diagram. I for one thank him as the board is one sided and not that big, so defenetely helpful, but needs tweaking (again) as of course, no Eagle files, just PDF  :(.
According to « Reply #797 on: February 03, 2011, 08:31:47 PM » there is a fault on that drawing. I did not check, too much fun.

5. Red Baron posted the part list with the discrepancies, which helps a lot. If anybody wants to build this "fun" project with posted boards I suggest to get this discrepancies file which he politely called: Parts comparison 0 - 30V 3 or 5A Power Supply.pdf (somewhere page 100 or so... cannot remember).

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Guest liquibyte

I've been working on a dual version of this and have decided to have the board made.  This is what I have so far, any critiques are welcome as I have never designed a board for production before.  The reason that it's laid out this way is because I am trying to fit two of these on one board that measures no more than 10 centimeters sqare.  I'm also including the schematic and board files if anyone wants to take a look or if they can be useful.

post-107142-14279144639608_thumb.png

30V.zip

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Hi Zinci,  Welcome to the forum.  It's good to hear a new member's perspective of where we are.    I think there is one basic design that that been fairly consistant.  Audioguru reposts the sketch about every 2 pages because of the tremendous number of pages to weed through but that basic sketch is shown on the first post and the parts are listed on the 2nd post.    Sure there are two trimmers without part numbers but the values are listed.  If you look at the photo of my board (built off the sketch shown) you will see a date of 9/25/08.  Note that that design is still current despite 5 years of discussion.  Sure we might have tweaked one or two component values but it works fine.    You are correct I didn't post the .sch file because it was my first Eagle attempt and it was/is  a mess.  I never bothered to clean it up so I never posted it, but the board file could be used to make pcb's.  I built a 30V 3A version, a 50V 5Abut all have the same basic  design layout.  Just for the fun of it, I built a SMD version by taking my original Eagle .sch and changing compontents.    Many individuals post sketches during the design and build phase  but how do you know they work?

There might be minor component changes but many are preferences.  For example, the heat sinks for the 3055's run 9 times the cost of the transistor.  While the 3055's output transistors are readily available, economical and work fine, I prefer to use a beefier and more expensive MJ11016  given the cost of the transistor is incidential to keeping it cool, and I can delete the heat sink on the BD139.  I prefer to use a .027 ohm sense resistor instead of the 0.47.   

If you use the sketch on the the first post and parts on second you will have a proven design that has been built by many users.  I will bet if you build the board a couple of times you will likey change a few parts to suit your preference.  Good Luck.

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Liquibyte,  I assume you are going to eventually have a  some sort of display.  You may want to determine if you need any connections from your board to the microcontroller for power. If you want to display the max setting of the current control, will you need  to measure the voltage of Pin 3 on U3?      Another decision, do you want to add "green power on" led for the board indicating both boards have powered up?  On my board I had one onboard led for current control and a set of jumpers for the LED on the case.  While testing I didn't have to bother with hooking up a led.  Are your power paths wide enough (I did not examine ). 

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Guest liquibyte

Liquibyte,  I assume you are going to eventually have a  some sort of display.  You may want to determine if you need any connections from your board to the microcontroller for power. If you want to display the max setting of the current control, will you need  to measure the voltage of Pin 3 on U3?      Another decision, do you want to add "green power on" led for the board indicating both boards have powered up?   On my board I had one onboard led for current control and a set of jumpers for the LED on the case.  While testing I didn't have to bother with hooking up a led.  Are your power paths wide enough (I did not examine ).   

The displays I'll be adding later will be powered from a separate power supply that I've already made concessions for in the case.  I've been getting feedback on the board design on another board and will probably be redoing the traces to shorten everything up and not be as meandering as they are now.  I was going to measure accross "R7" to display the current value but didn't know I could do that with U3.  Did you put in a header to do that, can you elaborate on that part a bit?  I'd definitely like to do it that way.
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liquibyte,  R7is the sense resistor, meaning if you measure the voltage drop across the resistor you can determine how much current is being drawn using I = V/R.  If you use a microcontroller to drive your display you can utilize one of the ADC pins to measure the voltage drop in order to compute current.    Likewise Pin 3 of U3 controls the current limit of the device.  For example if you set Pin 3  to 1.0V  (by adjusting P2) then there will be no current cutoff until I = 1.0/0.47ohms = 2.1amps.  By also hooking up another ADC pin of you microcontroller to Pin 3 you can measure the voltage on Pin 3 and display what the current control is set to.  Without a display you don't know the current limit setting.   

By the way, R7 is typically a 5 to 10W resistor that takes up a large chuck of real estate.  I didn't see anything like that on your board so I assumed you were mounting it to the frame.  If not you may want to make adjustments.

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Guest liquibyte

I'll attach a pic so you can see what I'm attempting.  It's rather large just so you know.  At the bottom, you can see green and black wires running off screen, those are the current sense resistors.  Chassis mount, gold aluminum etc...  Mine are 0.47R 16W though.

post-107142-14279144640034_thumb.jpg

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