Hello anniel747

So you highly regulated 5V is only for LED.

Leds and lm324n inputs



please I will appreciate your help if you can answer only this question

Can I do not add the caps after the 5v chip and in the same time i keep the good regulation given by 12v chip and his caps

 

Your design makes no sense.
Why do you need +5V on inverting and non-inverting inputs of an op-amp with open loop gain?

Let me rephrase that:
1. Why is op-amp with open-loop gain?
2. Why inverting and non-inverting inputs at the same voltage level?
3. What is so important about +5V?

 

What is the use to providing 5V to all inputs? A simple divider can get 5V from the 12V rail. No, not good practices

i said in #08 post

The maximum loads required for each regulator:
1- +5v for three voltage divider there inputs are in lm324n both (inverting and no-inverting), 2 leds
2- +12v is for lm324n as comparator and amplifier, relay (400 ohm)
I don’t think that I have big loads!?

Your design makes no sense.

please i don't have a problem with my design or at least now !!

please I will appreciate your help if you can answer only this question

Can I do not add the caps after the 5v chip and in the same time i keep the good regulation given by 12v chip and his caps

and thanks again

 

My first question was like the title indicate “Two regulated and fixed voltages +5 and +12”

And not about my design

I am sure that the members of this forum are helpful persons even you, but I think not in this day

Thanks and see you again

 

We are realists and we design what we know works and avoid what will not work.
You can come up with hypothetical ideas but there is no point in discussing a design for imaginary ideas.

The bottom line is you do not need +5V input to your op-amp and you do no need +5V to power an LED.

 

You just proved you have absolutely no need for a 5V voltage regulator

No, he didn't.

While I agree that powering one LED off the 12 V makes sense, the 5 V supply is the power source for whatever produces the variable voltages.

No matter what devices are used for the 12 V and 5 V regulators, double regulating the 5 V will improve its stability.

I would leave the continuous LED connected to the 5 V to indicate that that source is awake.

ak

 

The variable voltage can be as easily be supplied by the 12V.

You don't know that. The variable voltages could be coming from5 V-only sensors or circuits.

There is too much mysteries around the circuit to really know what amount of regulation is needed.

After post #8, there are no mysteries. He already has determined the correct regulators for his job. That never was his question. His original question was about running the regulators in series or parallel, and after post #8 I think there is an advantage to series.

He wants to use 12V because he has 12V relays and 5V because he has 5V regulators.

Sounds like good inventory management to me.

ak

 

TS does not want to come clean and tell us what he is trying to accomplish with his top secret project.
For all we know TS just wants to built a personal test bench with +5V and +12V supply. Fair enough, that is a good enough reason for two supply voltages.

If that is the case, two voltage regulators in series vs two voltage regulators in parallel, that is the question.
For fixed loads, the total power dissipated is the same. It comes down to how much power is dissipated by each regulator.

Series connection
12V regulator has to dissipate about (4V x total current) W, assuming the raw supply voltage is 16V.
5V regulator has to dissipate (7V x its current) W

Parallel connection
12V regulator has to dissipate about (4V x its current) W
5V regulator has to dissipate (11V x its current) W

Result
12V regulator has to dissipate more heat in series compared with parallel connection.
5V regulator has to dissipate more heat in parallel compared with series connection.
Total heat dissipation remains the same.

Bottom Line
Which ever configuration you choose make sure that both regulators are mounted on large heat sinks.

 

You know best! Top-secret system with magic circuits no one know where they come from are seldom easy to guess.

I truly do not understand your focus on irrelevant details. Of course it always is better to have more information when answering a stranger's question. But "top-secret" - ? No. Magic - ? No. There are external circuits that he already has determined will do what he wants with a 5 V supply. Nothing about that is "magic", and your characterization as such gives him way more information about you than you have given him about his question.

I spent 20 years doing rugged electronic systems for the military, without a security clearance. Many times I had to design something to interact with a system about which I had the barest of interface details, or to meet a specification I was not cleared to read. Turns out that once you check your ego at the door, it's not all that hard.

I call the unknown aspects of his project irrelevant because if you go back to his original question in post #1 and the added detail in post #8, nothing else is needed. He already is thermally aware, a significant advantage over most students. He wants to know if there is an advantage or disadvantage for one method over the other. ***Based on the information he has chosen to give *** (after all, it is *his* thread), there is.

ak

 

Experience is a great teacher. Maybe it is best to tell the TS what he wants to know ans let him get on to the next discovery If he wants more help he can ask.

It seems that the 5V supply is lightly loaded it probably doesn't make much difference whether he goes with two "parallel" or cascaded regulators.

Just as it looks from my point of view.