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lighty
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Posts posted by lighty
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Hi Lighty
Is this what you were thinking of making?
Yip, started something but have been caught at at work, need to spend some time on it. -
Ok, thanks
good advise! -
I'm wanting to add a Fine Adjustments pots to the circuit for the vltage and current, as I find the Pots are very sensitive.
I was thinking of putting a 1K Pot between P2 and R18, and P1 and the output od U1.
Would this work?
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Hi PicMaster
I wasn't intending to control the PSU with a pic, but rather just use the voltages of the wiper to show where the Voltage and Current pots are situated.
Eg, lets say the Vpot is set to 12 and current to 1 Amp, it would show this on the LCD, along with the realtime Volts and Amps. but at least you know the PSU wouldn't deliver More than 1 amp should something go wrong, wouldn't be nice to find out that the pot was set at 2 Amp... similarly for the voltage, to pervent over voltage should the load drop from the PSU, while you have something else connected to... If you know what I mean?
I suppose you could use a tandem ganged Pot, using the second Pot to drive the "SET" voltages to the pic. -
Mmmmm
Ok, the "SET" values don't look like it will work, the voltages change when circuit goes into CC. :( -
Ok, now that I have eventually got my PSU unit working 100%, I'm wanting to build a LCD Display for it.
I'm hope to have the following displayed on it.
Actual Voltage
Set voltage
Actual current
Set current
Temp of heatsink
So here is my question, once calibrated, are the voltages from the wipers of P1 and P2 linear to the voltage and current limits, Or would the voltages change as the circuit regulates the voltage/current? The reason I ask is I'm wanting the use the ADC to read the voltages (through voltage divider resistor) from the the wiper to show the "set" V and I.
Would this work? -
Thanks for all your patient help.
Tested to 3amps! all ok -
I feel like a idiot now >:(, you have hit the nail on the head, only one of the 2N3055 cases where connected to the +35V.
Will connect both and test! -
I have checked Emmitter voltage of the Q2 and it is same as the base voltage of the 2N3055's, when Voltage pot set to 0V as per previous post, but I will check again at say 12V.
I will go through the board again with a fine tooth comb, Like I always say "if it wasn't for bad luck, I wouldn't have any luck at all" ;D -
I understand what you saying Audioguru, and thats why I'm so confused.
I definately seems that the BD139 is taking all the load, hence it pops at anything over 1.5 Amps.
Sorry, that was a typo, was meant to say Q2 gets warm (quick short circuit of output on a fair size heatsink), but doesn't get extreamely hot.
Redwire, I do have them on a heatsink, but not very big, so I would expect them to heat pretty quick, but they don't.
R17 is now 68ohm.
I've also check R16, its correct @ 1kohm. -
???
Just not winning, I happy with the voltage reg side, but I just popped another BD139 while calibrating the max current (by shorting through a multimeter), I had voltage set to about 12V-14V, the VR3 set to min current, I shorted the output (for 1 second intervals) and slowly worked the current Pot up untill I reached the max position, which was about 1.4 amps or something, I then started increasing VR3 to increase the max current limit (1/2 turn at a time so to not over shoot the 2.5 amp limit I want), but at about 1.7 amps, Q2 popped. It was getting warm, but extreamely hot.
Q4 and Q5 where only just above room temp, almost as if they weren't taking any load?
I'm ready to shelf this board and start again...... Please help -
Cool, Thanks again for all your help.
I will load the circuit and let you know.
Cheers -
Ok, replaced Q3, LED problem sorted.
Replaced D11.
Tried 2 new 2n3055, output voltage of 0.22V with a 10K resistor across outputs.
U2 output still at 0.08V?
VR1 still makes not difference. -
The 2N3055 are brand new, but will try another set.
Will also replace D11.
R19 and R20 are correct, I will try replace Q3 and then U3 -
Hi
Hope this is what you are looking for :-\
Voltage across C1 = 35V
Base voltage on BD139 = 0.08V (same as output form U2)
Collector Voltage on BD139 = 35V
Emitter Voltage on BD139 = 2.055V = Base voltage on Q4 & Q5. (suspect this is a problem if I understand correctly?)
Emmiter Voltage on Q4 & Q5 = 2V (without any load)
I also check R16. just to make sure.
Should I increase R17 up more?
Q3, is situaled correctly, will double check R19 &R20, perhaps some flux could be the cause?
Thanks Audioguru! -
Ok, here the findings, no adjustments between measurements.
U2 in+ = 35mV
U2 out = 76mV
Voltage Pot high = 11.32V
Voltage Pot Low = 0.9mV
Voltage Pot Wiper = 1mV
PSU output Voltage 2.2V unloaded, 300mV with 10K resistor across output. (electrolytic cap ? problem)
VR1 still makes no noticable output change.
Changed R17 to 68ohm, no noticable difference.
LED has slight glow all the time, even when not in "CC mode"
I did try replace U2, made no difference. -
Thanks for the prompt reply!
So what I will do :
1 - connrect C7
2 - Check input of U2 with V Pot at min, should be 0V
3 - Check output of U2, should be +1.4V
4 - Try replacing U2
5 - Increase R17 to 68ohm (what I have on hand)
Will report results shortly
Thanks -
Forgot to mention, the BD139 is on a medium size heatsink, but doesn't even have time to heat up before popping.
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Hi Audioguru,
as soon as I'm able to take 1 step forward, I have to take 2 steps back. ???
1st some background info you may require:
- Transformer is 25V AC rated 5amp continuous.
- Redwire's PCB.
- Your Parts listing - using the TLE2141.
- 2x 2n3055 and 0.47 10W.
Problems
1 - BD139 keeps popping when I load (short) the supply (with C1 now connected). While trying to adjust RV3 to set the max current, the DB139 pops. what I do is, adjust the current pot down to min, slowly adjust it up to about 2Amp, when I get there (only shorting for about 1 second), I adjust the VR3 down, (adjusting both in steps on after the other if you know what I mean?) until I have adjusted the pot to max, but when I have adjusted the current pot to max and I short the output, it pops the BD139, within 0.5 seconds.
2 - C7 popping, C7 has being blowing up quiet regularly, so much so that I've now left it off for last, I think this be caused by leaving C1 off during testing?
3 - need to set Max Voltage VR2 to 25V (think this is what you advised for my transformer VA at 3amp?) but can't get it lower than 25.4V - not a major problem probably need to adjust the value of R11?
4 - Can't get the 0V to 0V, lowest is about 0.7V, RV1 seems to make no difference, even without C7 and with a small load.
5 - When Current pot set to min, current limit LED comes on. This is to be corrected by increasing R17 from 33ohm to about 39 to 47 ohm?
Please can you help.
thanks in advance! -
Hi lighty,
In in my eagle file that you posted I noticed that you don't have the ground plane filled under the power resistor (blue outline on left hand side). In the Eagle program, hit the ratsnest button and it will fill automatically. Without it filled there are a few connections that may not be connected. I should remind users because the standard default for Eagle is to not fill these areas when the file is first opened.
Thank Redwire, I was aware of that when I made my boards, was just too lady to do it for the screen print. -
Sorry you right, it is Redwires'
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Your PCB is very negligent drawn.. Don't use autorouter, where you can draw PCB on your own. This one is really easy, especially if you have double-sided board like you..Just for an advice, your PCB could be much smaller for double-sided board, and much more accurate..
Fikic, this it the PCB done by Audioguru, not mine. Which in my optinion is perfectly fine. -
Audioguru / Adyhansolo
I might be way off of here, but learning from my last problem (previous page)
I didn't have the header pins for the off board LED soldered in place when I testing, this cause the C7 (rated 50V) to pop within a few sesconds of powering up. I assume it is due to the one pin is acting as a "via" to gound some of the circuit, could this not be Adyhansolos' problem?
Just a guess :-\
Image attached.
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Hi Audioguru
I seem to be having a problem, I've just finished the second board and while testing, C7 explodes into pieces about a 1 or 2 seconds after I power up, I replaced it and the same thing happened again. The transformer is the same one I use on my other board, so it can't be it.
any idea where I can start? as I can test without powering it up?
When I powered it up the 2nd time, I had my meter on the output, and it seemed to sit at about 30V.
C7 where 10uF 50V electrolytic.
Thanks
Ok, found the fault, didn't fit the header for the off board LED, which one the the legs acts as a "via"
Will get new caps tomorrow and test again.
0-30V Stabilized Power Supply
in Projects Q/A
Posted
The MC24072 is a dual opamp configuration, it should work but its not a direct replacement part, as the pinout is different, but if you can work around this, then I'm sure you could.
PS, you will loose the offset too. but not a train smash though.
Thats just my opinion, perhaps wait for some pro's to answer.