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PicMaster
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Posts posted by PicMaster
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I was able to open it try this one I've zipped it up
see how you get on -
why do people need to waste time on simulating the design beats me, The PSU works perfectly has it so in my eye why try and reinvent the wheel.
I've found from past experience simulating don't always to seem to work like they do in real life. you can't feel the monitor for heat ;D -
Hey Guys, I'm building this power Supply, using the Excellent PCB designed by PICMASTER (3-5A version), Can any one please tell me or point me to a post that describe what the Trim Pots RV1,2,3 does, thanks a lot.
Thanks for the comment, -
Mmmmm
Ok, the "SET" values don't look like it will work, the voltages change when circuit goes into CC. :(
You could not have set voltage anyway, You could set the voltage with the wiper but you would have no way of limiting it, if you where to move the pot. The only way would be remove pots and use PWM from the pic. The same goes for the current control. You can read real time voltage,current and temp of the heatsink,
I did sometime time ago remove the pots and used pic to control the PSU but never got around to finishing it may be I will blow the cob webs off it and start again.
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I remember now why I created a new BOM is that some of the parts do not exist now like the .33R power transistors resistors . I will check that all the values are correct and I have decided to leave my version has it is, After all it is so simple to cross reference between the two drawings and BOM but I can't see the reason or nay need to, Has I built my PSU off my version including the bom. I will correct the last sheet which is the Assembly drawing
morpheous87 I would try 47R then 51R and just increase it a little until it works, I never had this trouble with mine -
How exactly to null it? I'm using PicMaster's schematic and there isn't R17. What value it should be?
R17 is R16 on my schematic They are both laid out the same order so you can cross referaence from the original version. If I get time I will correct my version so it's the same has the original -
This is PicMaster's PCB. I have a question about the PDF. The white print on page 3 and the PCB connection on page 6 aren't same. The parts names and their places are different. I think the white print on page 3 is the correct one, but am I right?
I will look into it and let you know, Your the first one to spot it. -
I've noticed something new:
If I have pot for voltage adjustment set to maximum value and I am changing current limit pot value from minimum to maximum, something strange happens. At it's minimum, output voltage is 40.5V. Then I am slowly raising it. The output voltage stays 40.5V for about 1/4 of a circle, then it starts to fall to 30V, and then again raising to 35V, and than finally falls to 24V at maximum value of pot for current adjustment. I don't understand. Is my pot broken?
So you have used Audio's schematic ?, Did you redraw the schematic and then transfered the design over to the PCB package then once you laid it out you ran the DRC rule checker ?
or Who's PCB layout you used ?,
The only reason I ask is if you have just laid out the PCB yourself just from the schematic then you could have errors in your PCB.
When I did mine I redrew the schematic check it and double check it against the orginal then transfered the design internally to the PCB package, Then Laid out then design then ran the DRC rule checker this tells me that it is 100% routed and error free. Mine worked first time has it should whenI built mine. -
Here it is:
Looking at your PCB the output tracks are still not big enough to take the current for 5A and yes the pads need upgrading.
Here is the modified version this will either do the 3A or 5A version, For the 3A just leave out Q3A & R20A
For the 5A change R7 must be 0.27 ohms/10W (TB4 or the 2 holes either side), I have not updated the BOM yet but should be easy to workout -
So, the PicMaster's PCB need a little change for the third transistor?
Yes it will require a little Mod, I only built the 3A version I've never really as the need for 5A, The mod is esy to do you can just hardwire the third transistor onto the exsisting tracs just solder the emitter resistor straight onto the pin of the transistor. I can mod the pcb to take the thr third transisor
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I am planning to use 24V/250VA transformer for this project, since this is the only one I have now. Is this ok? What is the difference if I use 10000uF instead of 12000uF for C1 (for 3A design)? Has anyone tryed to draw single-sided PCB for new 3A project?
PS: I drew PCB in Ki-cad. Can someone, please take a look at it and tell me if it's good? If it is, then others might use it too.
Yeah I did and you can download it from here, It's single sided and it can be 3A or 5A your choice -
Hi,
i've build this one from PicMaster, but on first attempt i got little firework with fog, both U1 and U2 are gone (cracked) :( does anyone have advice what can be wrong? i have C8 ~ 20000uF
could it be due to power transistors? (transformer, and 2n3055 's are the only parts which survived from my last attempts)
How can i troubleshoot it?
a) can i remove OPAMPS?
b) can i disconnect power transistors?
c) what else i can do?
I never had that problem, Have you checked that the bridge rectifier is correct ?
I used one like this from here
http://www.rapidonline.com/Electronic-Components/Discrete-Semiconductors/Bridge-Rectifier-Diodes/4A-8A-In-line-bridge-rectifiers/29673
It's like audioguru stated it must have been power supply voltage is connected backwards or the op-amps aren't the correct ones. Has it is remover U1&U2 and see what voltage you have got on pins 7&4.
Or have you found your error or a fault, means you thaked audioguru but you do not say if problem solved
I know my design works 100% otherwise I would of not published it -
You could do what I did went to the Texas instruments web site and ordered some samples then you get them for free.
You need to listen to audioguru the old design has many faults, I have ben there and done that tried everything to get the old design to work but in the end it went in the bin and I designed my own PCB of the upadted schematics and have had no problems.
There is lots of information in this topic. -
It is sized 1:1 and it does not need to be mirrored.
When you go to print it just make sure the the page scaling is set to none, This is how I did mine and it worked perfectly. -
I looked in your project, and I have some questions. Can 24V input from transformer be used?
And can 2N3055 be used instead of TIP3055?
Yes a 24V transformer can be used but you will not get the full 30V plus you will suffer a higher ripple at max voltage set to max current, This would be ok if only want 25V PSU
Yes you can use 2N3055 instead of TIP3055
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This is my version of the PSU , All tested all working no problems complete with PCB and BOM aslo with connection drawing, I mounted the transistors on a seperate PCB but you don't have to use the PCB you can just hard wire them.
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Has anybody made this very old project work properly?
It will probably work properly if it is built according to the datasheet for the IC.
I brought a kit from Velleman which was based om the ICL7107 and I found that this gave unstable readings and could never cure the bouncing of the readings, May be this is why they stopped selling it ?
So in the end I decided to design and build my own based on the MAX7219 and PIC16F876, This gives accurate and stable readings and is now used in my Velleman PSU 0-30V 0-10A, I used ISIS to simulate it to get everything working(Picture attached) and then designed and built the PCB for it.
I like the idea of LED'S because where my PSU sits at the back of the bench I don't have to lean forward to see the LCD version. Plus I use the green version which is better
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I forgot to add the latest schematic to the PDF file
Picmaster -
Here is my vesrion of the power supply comlete.
PDF file is a new BOM(for this project only),PCB copper side, PCB overlay, assembly drawings
Please let me know if you find any errors or suggestions
Picmaster -
Here is the working version on my PSU, There is just just a couple of minor things I have got to look into and clarify. Yes the connecting wires may look a little on the light side but this is for testing only Has I only took to 3amps and calibrated max current for a few seconds to try.
These are the minor things that I have got to look into.
1. Because I'm using a 30V transformer the voltage is slightly to high feeding the op-amps has the TLE2141 is only rated at 44V I got 48V.
2. With the current pot set to Min the limit LED comes and and this restricts the voltage I have to turn it up slightly(not sure what the voltage is at the center of the pot has it is getting late.)
Aslo I'm not sure if this is normal if the limit LED should light up with the pot to min, I did disconnect C10 has if I remember lighty had the same trouble but it is still the same
I get full control over the current range min current is about 40ma, I did see that is should only be 12ma, I will have to make sure that I've got all the correct components in place first and I will read through the older posts.
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I've got it 3/4 built, I missed some parts off and by the time I thought about it Maplins was closed.
will try and get them tomorrow (Monday) then I will be ready for testing and if all goes well I will upload the pcb
picmaster -
This is the connections drawing for my version of the power supply and updated schematic, To me it looks quite simple
This is the actual size of the PCB and what the layout looks like.
The next thing is to update the component values on the schematic and create BOM
Hopefully over the weekend I shall get PCB made and assembled -
Then your schematic is confusing like Redwire's since parts not on the pcb are not shown.
This is only the schematic I have a drawing explaining all the connections in detail, I t will be simple to follow, I'll upload the details in a short while
Picmaster -
You missed the second output transistor, the emittrer resistors for both output transistors and the emitter resistor for the driver transistor.
Thanks for that, I did for get to add the resistor to the BD139, The reason is I had the idea of having the BD139 and the ouput transistors and the emitteres resistors on a seperate board so they can bolt direct to the main heathisnk rather than have 2 heatsinks for them. I wll sort that out either add them to the main board or go back to the first idea,
PIC multimeter help
in Electronic Projects Design/Ideas
Posted
Hi All
I'm working in a project well a simple pic multi-meter based on on bench power supply one I have working ok, Now I want to make a portable meter of it now this would be ok if you made sure you got the connections the correct way roun, I know I could add reverse polarity diodes but I would like to some how have it where it does not matter how you connect the leads to the input the output to the ADin pin on the pic would read say 0-2.5V if the leads wrong way round(where I could display a - sign) and 2.5-5V if they was correct way connected or same again no matter how the leads are connected I get 0-5V to the ADin pin and then can add a circuit to go high and the pic chip looks for this, Now I've tried a differnational configured op-amp but no matter if there is no leads or whcih way round they go I always get a 5v output, Now this may be the way I had it set up.
What would be the best method and the correct way so no matter how you connect the leads up you get a 05V out to the ADin pin
hope you can understadn what I'm trying to explain what I'm doing
Thanks