# 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.

#### Johnson55123

Joined Nov 8, 2021
23

#### ElectricSpidey

Joined Dec 2, 2017
2,186
The resistor connected to the adjustment pin of the regulator is how you change the output voltage.

#### Johnson55123

Joined Nov 8, 2021
23
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
2,186
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.

#### Johnson55123

Joined Nov 8, 2021
23
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.

#### Johnson55123

Joined Nov 8, 2021
23

#### dl324

Joined Mar 30, 2015
15,471
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
15,471

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.

#### Johnson55123

Joined Nov 8, 2021
23
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

#### ElectricSpidey

Joined Dec 2, 2017
2,186
Last edited:

#### crutschow

Joined Mar 14, 2008
31,140
Keep the 220 ohm resistor and place a 1k resistor as a load.
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.

#### dl324

Joined Mar 30, 2015
15,471
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.

#### Johnson55123

Joined Nov 8, 2021
23
Do you have a 5k pot? A 10k pot may be using too small a range to give proper control.

A 2k pot would be even better.

Keep the 220 ohm resistor and place a 1k resistor as a load.

Be sure to place that output cap...I don't see it on you new schematic.

LM317 3-Terminal Adjustable Regulator datasheet (Rev. Y) (ti.com)
Okay.. thank you, I will get a 2k pot then replace 220 ohm with 1k as the load..

#### Johnson55123

Joined Nov 8, 2021
23
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..

#### Johnson55123

Joined Nov 8, 2021
23
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
39
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.

#### Audioguru again

Joined Oct 21, 2019
5,426
Almost everybody does not notice that the datasheet shows a more expensive LM117 in a schematic using a 240 ohm resistor. The writing says that a cheaper LM317 needs 120 ohms.