I'm trying to make a regulated charging circuit 220ac to 12 DC with the diagram below but my out put just remain constant, it can't be regulated.

Thread Starter

Johnson55123

Joined Nov 8, 2021
9
The resistor connected to the adjustment pin of the regulator is how you change the output voltage.
Okay.. the out put is 12volt. But if I try to regulate it down it refuses to decrease intend remain constant and then go straight by showing me 0.01volt, if I should try to increase, just with a little turn it will just go straight by showing me 12volt.. so it doesn't regulate accurately...
 

ElectricSpidey

Joined Dec 2, 2017
2,038
There could be any number of reasons why your circuit is not working properly, and you are going to have to give a lot more information to get any reasonable help, you can start with putting the values of the components on your schematic.
 

dl324

Joined Mar 30, 2015
13,857
Okay.. the out put is 12volt. But if I try to regulate it down it refuses to decrease intend remain constant and then go straight by showing me 0.01volt, if I should try to increase, just with a little turn it will just go straight by showing me 12volt.. so it doesn't regulate accurately...
  1. Is the regulator an LM317?
  2. What is the current set resistor value?
  3. What is the value of the output capacitor?
  4. Do you have any load on the regulator?
 

dl324

Joined Mar 30, 2015
13,857
1636597473516.png
A 220 ohm current set resistor isn't small enough to guarantee that the regulator will function. The datasheet specifies a minimum current of 10mA for correct operation.

The two electrolytic capacitors are drawn upside down. The 10uF cap is shown an non-polarized. It would be huge if they made 10uF.
 

Thread Starter

Johnson55123

Joined Nov 8, 2021
9
View attachment 252360
A 220 ohm current set resistor isn't small enough to guarantee that the regulator will function. The datasheet specifies a minimum current of 10mA for correct operation.

The two electrolytic capacitors are drawn upside down. The 10uF cap is shown an non-polarized. It would be huge if they made 10uF.
Okay, that you. But Which resistor that would guarantee the regulator to function well. Or will you mind if I should ask of a
 

dl324

Joined Mar 30, 2015
13,857
But Which resistor that would guarantee the regulator to function well.
The 220 ohm resistor will draw about 5.7mA. If you add a 2k resistor on the output, that would give you more than the 10mA needed. If you use a 120 ohm resistor, that will satisfy the minimum load current requirement by itself.
 

Thread Starter

Johnson55123

Joined Nov 8, 2021
9

Thread Starter

Johnson55123

Joined Nov 8, 2021
9
The 220 ohm resistor will draw about 5.7mA. If you add a 2k resistor on the output, that would give you more than the 10mA needed. If you use a 120 ohm resistor, that will satisfy the minimum load current requirement by itself.
Okay thank you for your support and the knowledge, I really do appreciate..
 

Thread Starter

Johnson55123

Joined Nov 8, 2021
9
The 220 ohm resistor will draw about 5.7mA. If you add a 2k resistor on the output, that would give you more than the 10mA needed. If you use a 120 ohm resistor, that will satisfy the minimum load current requirement by itself.
Okay thank you for your support and the knowlo
If you use a 120 ohm resistor (the value recommended for an LM317), that will provide a minimum 10mA load current (1.25V / 120Ω) to maintain load regulation for any output voltage setting.
Okay.. thank you. I'm going to change the 220 ohm to 120 ohm resistor..
, I really do appreciate..
 

old_beggar

Joined Jan 29, 2021
38
I think it would be prudent here to suggest reading the (easily available) LM317 datasheet - it tells you all of the above. It also gives lots of other uses for the versatile LM317.
 
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