78l33 circuit regulator, thought it would drop a 5v voltage to 3.3 v but no!

[DevonRevenge]

I get 4.8 volts or 5 volts, is there more to do or is it working wrong?

 

[Amar Dhore]

What is the input Voltage?
Make sure if its 78L33.
Do you a have a circuit?

 

[CDRIVE]

The ST datasheet does not list output regulation specs on inputs less than 5.3V. That said I think you have it wired wrong. Post clear photos of your circuit.

Chris

 

[DevonRevenge]

well its pretty simple, ja the input voltage is 5.2 but thats just me testing it, its gonna be something like 3.7 later on and the circuit is a test circuit so its in its most simple form

-- (_) <- the component
| - | - |
in out <-the other multi meter probe
^
The multi meter probe

hmm the post changed it a bit but you get the idea, just a test, so the voltage is too low, can you recomend a dufferent component?

 

[BobK]

It will definitely not work on 3.7V input. You need about 2V above the output. Look for a low dropout regulator, which allows a smaller difference between input and output.

Bob

 

[CDRIVE]

What are your maximum current requirements? If it's low you may be better off using stacked diodes and resistor configured as a shunt regulator. A pass transistor can be used to boost current limits if needed.

If you ask for a schematic of this I won't give you ASCII art. I hate it!

Chris

 

[DevonRevenge]

What are your maximum current requirements? If it's low you may be better off using stacked diodes and resistor configured as a shunt regulator. A pass transistor can be used to boost current limits if needed.

If you ask for a schematic of this I won't give you ASCII art. I hate it!

Chris

Okay thanks xD , I would like a schematic biut if im ordering parts perhaps im best off with just the one component, imtrying to reduce the components as much as I can, I need to theoretically make aa large number of what im making myself, what is a good low drop down regulamatator?

 

[DevonRevenge]

Will these be any good? LD1086V33 LD1086

 

[(*steve*)]

The LD1086 requires a little more than 1V to about 1.5V above the output voltage, so it won't work for you.

Knowing the current you require will help us help you.

Also not that low dropout regulators often require specific input and/or output capacitors.

 

[(*steve*)]

here are a couple of options.

 

[CDRIVE]

The best way to get pertinent and useful information is to answer questions when they're asked.

Chris

 

[DevonRevenge]

okay Im working with 3.7 volt 1050mAh battery I want a 3.3v output I have another 3.7 volt battery with a 2500 mAh output, that one is likley going to give me the power im supposed to have actually, but would like to try the other, I can provide a circuit diagram but im going to be changing stuff around a bit, the chip that needs power is arduinpo stuffs and oled displays n all that jazz

Forgive my impertinence ive been studying so much my mind is going floppy.

 

[(*steve*)]

OK, so your 3.7 V battery will be around 4V when just charged, and drop to around 2.8 when exhausted (assuming it's a lithium battery).

So a regulator with 0.2V dropout will be able to maintain an output of 3.3V until the battery voltage falls to about 3.5V.

You would need a far more complex circuit to allow operation down to a battery voltage below 3.3V.

 

[Colin Mitchell]

The first thing to do is answer this question:
How much current do you need?

You have been running around in circles with no possibility of getting a solution.

 

[DevonRevenge]

okay I will do this properly, tk for the focus:

 

[DevonRevenge]

Is that what you meant? I struggled to find more complex power data on any of the modules, the gsm module is the most unusual, it needs anything between 3.4v and 4.2!!

EIther way I am getting garbage from it which is why I wanted a better power circuit.

I have lost a lot of my understanding of electronics but I had studied it for a year and a bit in the past.

 

[CDRIVE]

You should be doing your experimenting using a regulated - current limiting supply. Not high Amp batteries that can melt things when you screw up. Also, you determine what a device draws by using an Ammeter. You should have one of those too. Use your DMM in Amps/mA mode.

IMHO, I think the garbage (your words) that your getting isn't caused by the difference of a few tenths of a Volt.

Chris

 

[(*steve*)]

if you have to use batteries, start with is small 9v battery and that original 3.3v regulator.

Whilst that's not current limited, the chance of blowing things up is somewhat less.

I would expect the current required to operate your circuit would be in the order of 40mA, but measure it to be certain.

 

[CDRIVE]

Now that's good and simple thinking Steve. Decided to have a dry day?

Chris