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Author Topic: looking for a +5v reference for power supply  (Read 644 times)
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sphinx
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« on: December 13, 2015, 02:47:30 14:47 »

hi

i am looking for a +5v reference that is connected to two potentiometers a 1kohm ie 500ohm to ground and the mid pin is connected
to inputs of two CA3240  today the 78L05(IC3) is used i would like to have a bit better one, i was searching but most seem to be very
low current.

schematic attached
if someone is goiing to use it there is a fault in it one component need to be added and pins on an op need to be swithed
at the moment i dont remember wich one so be CAUTIOUS
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« Reply #1 on: December 13, 2015, 07:02:07 19:02 »

You could look at Texas Instruments regulator LP2950. It is available in 5V version, and is pretty accurate (0.5%). It is as well more-or-less drop-in replacement of 78L05. The specific part number depends on which case you prefer, for TO-92 you find a few alternatives at digikey.com (https://www.digikey.com/product-search/en?pv48=1&pv1291=714&k=LP2950A&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25). The regulator seems to be quite cheap, and available from TI, ON Semi and Exar. I believe you can buy it in many places.

The only specific requirement relevant to this application I can see after a brief check of the data sheet is that the output capacitor should be 1uF or more for stability. However, the capacitor C4 in the design is likely good enough. The ESR requirement is not too tough. Some ceramics *might* have ESR lower than 6 milliohm, but all ordinary electrolytics and tantalum capacitors are for sure within the requirements.
« Last Edit: December 13, 2015, 09:51:27 21:51 by crunx » Logged
Wizpic
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« Reply #2 on: December 13, 2015, 07:59:42 19:59 »

hi

i am looking for a +5v reference that is connected to two potentiometers a 1kohm ie 500ohm to ground and the mid pin is connected
to inputs of two CA3240  today the 78L05(IC3) is used i would like to have a bit better one, i was searching but most seem to be very
low current.

schematic attached
if someone is goiing to use it there is a fault in it one component need to be added and pins on an op need to be swithed
at the moment i dont remember wich one so be CAUTIOUS
If you remember I did this in ALtium and laid out a new PCB to make it 5Amps, I did make a PCB but never got it working correctly, not sure if I still have it lying around or binned it, If you still have the original PCB working could you let us know which pin it is on the op-amp I can change it and try it again and upload altium files here for everyone This would be a good project to start again and use a micro to control it, I think I added the missing cap but not sure about the pin swap on op-amp
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« Reply #3 on: December 14, 2015, 01:51:38 13:51 »

i will check thoce references up and have  look at it.

and to wizpic i have all documents of it and scans i will just take a pic of the board as its soldered so the collection will be complete i will upload it all when i put it all together

sorry for not being in contact had a bad period and dad health and death didnt make my whiplash related stuff any better.
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« Reply #4 on: December 14, 2015, 03:40:44 15:40 »

here is everything about the power supply i got and some new pics i added not the best but its
all i can get

read the important file it contains some extra info i lost the extra leaflet on the project

also check the info folder for the translation file

i have used altium 15.1.15
i have only made the schematic its not placed nor routed

the usual password

have fun with it


CHANGES MADE IN IMPORTANT FILE PLEASE DOWNLOAD AGAIN I FOUND MISTAKES IN IT
« Last Edit: December 14, 2015, 06:38:24 18:38 by sphinx » Logged

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« Reply #5 on: December 14, 2015, 07:24:23 19:24 »

Quote
sorry for not being in contact had a bad period and dad health and death didnt make my whiplash related stuff any better.
Sorry to ear about that and it's no problem I've been busy and had stuff happen but all good now, I will have a look at the schematics and compare if all ok we could use my PCB with any errors corrected. I've had a quick look and must have took parts off and ben binned, Will see about getting all the parts together again at some point
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« Reply #6 on: December 14, 2015, 07:54:41 19:54 »

that would be great no need to do the same job many times. the transistor T3 should be mounted close to the
transistor cooling unit its a temperature sensor and power should cut off at +80celcius

i was also wondering one could use transformer with different output voltages to minimize power loss
similar to whats done in this video https://www.youtube.com/watch?v=mdOauVzY9OU

just for notice language on papers is swedish

man my mind is messed up today in schematic in altium please delete C18 it should not be there
its my bad sorry for the mistake, that if i havent done it already it must have slipped thru
« Last Edit: December 14, 2015, 07:59:47 19:59 by sphinx » Logged

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« Reply #7 on: December 14, 2015, 08:20:42 20:20 »

I've had a quick look through the schematics and they look the same, But looking at the scanned schematic on IC4 both of our schematics R23 goes to pin 3 on IC4 but in your important note you say
Quote
and pin 2 and 3 on IC4 needs to be switched its ok on pcb scans
its ok in altium schematic
Should R23 go to pin 2 on IC4 and not pin 3 of IC4 ?
But if you say it's correct on PCB then the schematic must be wrong, If I remember from previous testing when I had PCB built the positive side was working but not the negative side (may be this was the issue ?)
It's a shame you don't have the bottom of the PCB in colour, this would have made it easier to reverse it in splan has the grey tone does not work to well,

The way I do it is load colour image into splan, place all the components on the pcb copy all track then export the gerber files then import the gerber files into alitum then export it to PCB side after a bit of configuring so we know the PCB is correct and a bit at a time start to import the schematic and changing the schematic compared to PCB, I have done this quite a few times and successfully cloned some PCB'S to obtain the correct schematic that I did not have, its a bit time consuming but fun
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« Reply #8 on: December 14, 2015, 08:42:02 20:42 »

the r23 is connected to pin 3 on ic4  so schematic is wrong but pcb is ok

i will try o make a scan with bottom in colour with components mounted dont want to desolder all components
again to do it without them
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« Reply #9 on: December 14, 2015, 08:54:24 20:54 »

I think it will be ok as is when I zoom in I can see it all ok, so don't worry about taking more photo's.
Looking at the scanned copy of the schematic R23 goes to Pin 3 of IC4 and looking at the PCB R23 goes to Pin 3 of IC4 or am I looking at it wrong. I will have ago at making the PCB the same but upated version rather than having the transistors mounted on another PCB, I f I remember we was going to make a 5 or 10amp version of it.
I'll let you know more when I've done some more work on it,
I have an idea to use Arduino with 16bit dac to control it using a rotary encoder to set voltage/current but we need to get this working first just thinking ahead  Smiley
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« Reply #10 on: December 14, 2015, 09:10:14 21:10 »

no you are completely right bout ic4. is my mind that fuzzed up today.

from what i remember i thought there was some op with switched input in this shematic
and thought it was ic4.

now i need to check all of them to see if they are right
i  need to let this be for today and check tomorrow with a clean slate
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« Reply #11 on: December 14, 2015, 10:54:20 22:54 »

OK I will check to but it will more than likely be Wednesday as I've been working on a data logger project (which hope to share soon with PC software to view data) and I'm out tomorrow night, Not enough hours in the day or week
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« Reply #12 on: December 14, 2015, 11:47:46 23:47 »

here are new scans in colour from 200 dpi to 1200 its the best i can do, i had to install a virtual
machine in vmware using windows xp since no drivers for anything newer than that
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« Reply #13 on: December 15, 2015, 04:50:47 16:50 »

i have now made a corrected package with the latest changes to important file
please read it, and added the colour scans hopefully no more changes needs to
be done.

sorry for all inconvenience it might have caused. my is not as clear as it used
be. due to medication and other whiplash problems i got. i try to do my very best.

the usual password

have fun with the design

p.s.
there might be someone else that also has built this unit and still has the papers on it
and the extra info leaflet with the written corrections, if you have that paper please
inform us about whats written on it. the designer JAN SOELBERG has written two books
with lots of schematics and designs this power supply might be in one of those books

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