Can't get 5v from AMS1117 5v regulator

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
hi,
If you are confident that its a adjustable, make R1 a 220R, R2 a 620R and use a 9V dc input, don't forget the 10uF across R2.
What is the 5v driving into, ie: load resistance.?
E
In theory your calculations same with mine. The r2 / r1 ratio is 3 always. But it just does not work I dont know why.. Maybe the chips are really bad.
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
Wire it accordingly then.

Ground the gnd pin, what output voltage do you get?
If I connect directly to GND it burns quickly but getting 5V for a short while as I described before. When I use with resistors I cant get what should be. Really stucked.
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
In theory your calculations same with mine. The r2 / r1 ratio is 3 always. But it just does not work I dont know why.. Maybe the chips are really bad.
I will use it as MCU powet supply by the way. The board needs 50mA apx totally with all leds and etc. Nothing special..
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
I would check the authenticity of the chip. I have a Chinese chips 74xx and 4xxx that dont work under feedback configurations that should work with real parts.
I suspect there is a chance that your regs are faulty.
After all experiences today, you might be absolutely right. I asked lots of questions to the seller and just waiting the answers.. Probably these chips just really bad and does not work, I wish not..
 

hp1729

Joined Nov 23, 2015
2,304
Hello. I'm obeying schematic rules but can't get 5V from the AMS1117 5V regulator with this schematic (see the attachment please). Input and output capacitors are 22uF and here the results:

R1=1K, R2=3K -> 1.6V~
R1=47, R2=150 -> 2.55~ and R2 is so hot.

If I dont use resistors, the output is 5V for a few seconds and then decreased to 1.6V and then the regulator is burning.

What is wrong with this cheap regulator?
Which AMS1117 do you have? Does the "5 V" version need the resistors. Your schematic would be correct for the adjustable version. What voltage in?
 

hp1729

Joined Nov 23, 2015
2,304
Hello. I'm obeying schematic rules but can't get 5V from the AMS1117 5V regulator with this schematic (see the attachment please). Input and output capacitors are 22uF and here the results:

R1=1K, R2=3K -> 1.6V~
R1=47, R2=150 -> 2.55~ and R2 is so hot.

If I dont use resistors, the output is 5V for a few seconds and then decreased to 1.6V and then the regulator is burning.

What is wrong with this cheap regulator?
Chinese vendor? Another horror story. How much did you save by buying from that vendor?
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
Chinese vendor? Another horror story. How much did you save by buying from that vendor?
I bought these chips while buying LCD touch screens actually, didnt order specially, I know they are so cheap. I gave 45 orders so far in last year and this is the first faulty I think, the seller did not asnwer the questions yet. Sorry for all if they are really faulty. Thanks.
 

atferrari

Joined Jan 6, 2004
4,764
Not that this will solve your problem but a simple thing you can always do is to verify what pin has continuity with the tab. At least you can confirm if what you have matches the pin out in the datasheet.
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
Not that this will solve your problem but a simple thing you can always do is to verify what pin has continuity with the tab. At least you can confirm if what you have matches the pin out in the datasheet.
I checked the pins with multimeter in diode mode, tab is connected directly with center pin. And the center pin is Vout.
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
Well, the regulator is not faulty and connections are true. So how does not it work? After all days I see something and really dont know how I missed this but I used tantalum capacitors and its polars different as positive and negative, so, err.. it was shorting the circuit. I m so sorry, it was my fault. Thanks for all.
 

Thread Starter

zaferaltun

Joined Aug 31, 2016
65
Thanks for the update.
I am amazed that the tantalums did not explode. Mine always do... very dramatically.
I was cheking the component temperatures with my finger quickly and unplagging the power source if I feel really hot, lol. But one of them exploded yesterday and I started to think really deep, because the regulator chip was new one which is bought from another trustful store. So I checked every detail and you know the result..
 

dannyf

Joined Sep 13, 2015
2,197
1117a are readily dismissed by many as a shitty chip, when in fact it is one of the best in my view, for low ldo, resistance to oscillation and low cost.

Many people dismiss it out of ignorance, or group thinking.
 
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