DESPERATE TIME DESPERATE MEASURES WITH MY POWER SUPPLY!

Apprentice_Engineer

New Member
Ok so, building a 15v power supply...need help , like serious help..

I mean willing to maybe skype me help lol

I know a good bit about it and everything but it seems im getting no where..

I have a deadline to turn this in by ;(

I have all the components, schematics, everything..

I just need a little guidance..

It has your basic zener diodes, capcitors, reistors, transistors and op amps...ughhh
 
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One thread is enough. I have deleted your other one. Please carry on the conversation here. Also, typing in all caps is not necessary, and generally frowned upon by the members here. I have edited that as well. Please do it yourself next time.

Anyway, you say you have everything, yet you are not showing us any of it. How do you expect us to help when you don't show us what you have?

This forum is not for giving out answers to homework questions, so we really need to see what you have tried so far. When you have a specific question, then feel free to ask.

Regards,
Matt

P.S. Something tells me you would not be in such a rush if you hadn't procrastinated and saved this for the last minute....
 
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True, i did try to do it on my own at some point, but putting in a diode wrong, frying components made me frustrated!

I will add pictures of it, right now

and yea my deadline is the 20th
 
Ok, so what's your question?
 
i have finished stage 1, now one to stage 2, installing the chips and such, for some reason..my chips arent giving me the right voltage..When i turn the pot one way im getting around 16 which is int he ballpark but when i turn it the other way it stays on 16v. I then switched pots to see if it was the pots, and it wasnt. So im a a stage where i just want to have help i guess while im building it.. to ensure i dont "blow" any more diodes....

It sucks..
 
Can I ask a question? Why didn't you start out with a full wave bridge rectifier and a center tapped transformer?

What does the voltage look like at point 1 and 3 with a scope?

Is this supposed to be a tracking supply?

Which diodes are going south?
 
If you are just checking out stage two ... where did you connect R22 and R9 ... the other end away from the negative input terminal of the OP AMPS ?
 
What actual measured voltages are there across zener diodes D4, D8? What are the measured voltages at points 2 and 4?
 
Am I being really dim here, or does Q4 not make any sense? At no load, it's Vb ≈ Vc, and under load Vb > Vc. In either case Ve will be about 1.5v > Vb. Bonkers if you ask me, but I'm a rank amateur and don't know anything...
 
throbscottle said:
Am I being really dim here, or does Q4 not make any sense? At no load, it's Vb ≈ Vc, and under load Vb > Vc. In either case Ve will be about 1.5v > Vb. Bonkers if you ask me, but I'm a rank amateur and don't know anything...
Click to expand...

It's simply drawn incorrectly - the emitter and collector are reversed (check Q8 below, which is shown correctly).
 
That's pretty bad, in what I'm guessing is an educational text-book. I did compare Q8 - that one makes sense!
 
There are several things about that circuit which do not make sense or are just plain weird.

The half wave rectifiers
The LED fed with AC
The power supplies for the op-amps
What are the op-amps doing which feed the voltage adjustment pots?
The current limiters on the output, apart from the incorrectly drawn transistor, they seem to be working by shorting the output of the op-amps.

JimB
 
I know this project has it flaws, but thats the schematic he gave us. Block diagram, i can get that, gimme a sec.
I perfected stage one this afternoon. Im getting all the voltages in the right areas! Right now, I need guidance whilst going on to wire stage 2 of the project. Although the schematic is clear, im still a little leery. Im tired of replacing components.
So i guess im just saying if anyone has the time to overlook this with me, please do let me know..
either VIA Skype or whatever, idk

**tommorrow im going to bug and try to steal the radioshack guy, but chances are he just has the job, to have it and has no prior knowledge on this subject (based on my experience with one employee)
 
Pick up a couple of light bulbs for F1 and F2, Yep real light bulbs. Maybe 8 each of 12 v 1A lamps. Use for in series for F1 and 4 in series for F2.

If you pick them right the worst that can happen is the light will glow.

Or even a couple of 7 W night lights (the incandescent ones) in series with the 120 V AC line.
 
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