lab power supply

Your bridge rectifier is wrong.

Ed

LOL!! you have reason!! :) excuse me I have placed it without thinking I correct the outline immediately thanks ehsjr other problems relative the current control? that one is the part too much complicated for me have you got an idea for join the two current controll into one? the updated scheme:

thanks for the help

I have found an other error of distraction and I have update the schematics please criticize it :)

I think something is wrong with the +5 VDC supply. I'm not sure what is the purpose of Q5 and Q6, and the bases tie to each other, but nowhere else. Also, what is the raw DC voltage of +VCC and -VCC, and what is the specification of the supply? It appears to be something like 0-15 VDC at maybe 2-5 amperes, and the 7805 will provide 5 VDC at about 1 ampere. But if its input is 20 VDC, it will dissipate 15 watts. And the other series pass transistors will dissipate more than that. Also, the +VCC and -VCC connect to the power supply of the op amps, which are only rated a maximum of +/- 16 or 18 VDC.

It looks like the circuit is overly complicated for what is needed, and I think there may be other problems. This could be a good project for simulation using LTSpice.

I'd probably design it using a PIC!

Paul

Spend a little time discussing your small +5V design near the bottom. In particular, where the more positive side of it connects and I'm also curious about the roles of Q5 and Q6 and R24 and R25 in the context of the 7805.

Jon

when r108*imax it becomes approximately equal to the Q26 Vbe, Q26 is turned on ,it short circuit R109 and then switch off Q25 and it limits therefore the output current i copy it :) http://www.ortodoxism.ro/datasheets/fairchild/LM7805.pdf pag.23 fig.13

:) this is a problem.. i have may transforma at home but no time for searching the right one to use

yes i add the 5v regulator for force the zero volt transistors hold 5A but i don't have choose the transformer yet

I suppose that I will use an other transformer

this is the greater limitation but i don't know how to do otherwise

for having complete protection against the short circuits voltage tracking and currente regulation I do not see other possibilities :(

i try but seem that not exist a model for lm137, and I have problems when I simulate the single part with the operational the simulation of the circuit does not want to converge i'm not very expert with spice

a pic? how? controlling the levels with the dac? and the sensing with the adc? is not a bad idea therefore you could use a lcd but you would have to write the software and to the end you would only eliminate the three opamp..

now my big problem it's to group the two current regulation at the same one I thought to use the opamp advanced

many thanks for the answer!

I have corrected the scheme newly, led and the diode in the negative part was inverted this is the new scheme:

r108?

Q26?

R109?

Q25?

Yes... but... where did you get your value for 1k for R24 (that's waht appears on the schematic you posted latest), which corresponds to Rsc on the datasheet page? What figure are you using as the short circuit current limit? And you show 1k for R25, when the datasheet's corresponding R1 is 3 ohms? Why?

Jon

the necessity of the +5V is given from the problem that introduces the two regolators to supply 1,2 volt in place of 0 when refered to the ground. In the schemeI had not still connected the regolator of the +5 because I was estimating to connect it on a transformer to part, I would have intentional to use the same one but thinking that it would have been revealed useful to have a local power source for feeding logical TTL (that they consume a lot current) I have preferred to connect it to a transformer to part i copy it from http://www.ortodoxism.ro/datasheets/fairchild/LM7805.pdf pag.23 fig.13 but I am stupid and have mistaken to copy! lol! sorry! me of I was not shrewed not even when I have tried to explain the outline to Paul! excused! the problem is that in Italy it is late night :D and I am distracted of nature i correct the scheme:

many thanks!

excused me still

I see the tie-in, now. That's a beginning. But what about R24 and R25?? Exactly how did you calculate their values? What is the short circuit current limit you desire, here?

I roughly calculate hundreds of microamps and I have to imagine that the 7805 can handle that without any outboard BJTs floating about. And that if you really do want to limit the current to that tiny level, the circuit isn't going to do it because all it does is route the excess current via Q6 and then the 7805, neither of which will 'know' anything about the limits set up by R24 to limit what bypasses the

7805 via Q5. It's just shunted aside R25 and R24 + Q5 and back into the 7805 to hit its own internal limits, based on temperature and/or otherwise, instead. Do you agree?

Jon

r24 and r25 still they have not been calculates to you

1K it is the value of default of orcad I still do not know that transistor I will use for Q5

i understood.. you have reason this is very very beautifull

but an other lm317.. I will try to search an other solution wath do you think about the other part? the operational can work? i think that I will have to adjust some resistore value in the opamp schematic part but i do it under final testing have you got an idea on how to group the two current regulation at the same one? thanks for the patienz jon

creed that I will use one solution similar to this for the 5V protection:

me he seems good not? this other solution is brilliant:

I am trying to plan and to simulate my new protection:

with circuit foldback protection and pass transistor i think that I will use that for the +5V