# Current Limiter for Secondary Transformer

#### Amaury

Joined Mar 17, 2019
8
Hello there, newbie here.

Currently im trying to develop a current limiter thats going to attach to the end of a secondary transformer thats going to be used for academic purposes, but more exclusively half and full wave retifiers circuits.
I'm stuck in the part where the limiter has to output a maximum of 50mA.
I thought of using a isolating amplifier, given that they help control the current flow, but i would like more aproaches.

Apreciated the help
Best Regards

Joined Jul 18, 2013
19,461
A typical method is a crowbar circuit, there must be examples out there.
Max.

#### ericgibbs

Joined Jan 29, 2010
9,116
hi Amaury,
What voltage levels are required at the operating currents.?
Do want the option of setting the maximum current?
E

#### Amaury

Joined Mar 17, 2019
8
A typical method is a crowbar circuit, there must be examples out there.
Max.
Thank you very much, i'll dig unto that.
And comeback with a reply.
Best Regards

#### Amaury

Joined Mar 17, 2019
8
hi Amaury,
What voltage levels are required at the operating currents.?
Do want the option of setting the maximum current?
E
Sorry should've explain more detailed.
By the output wished you can see that it's a little transformer, so the values of the circuit won't be trespassing 25 volts probably, but it has to cover a large range of values, but regardless the output current should never surpass 50mA.

Thanks for the reply
Best Regards

#### ericgibbs

Joined Jan 29, 2010
9,116
hi A,
Couple more questions.
Is the 25V voltage RMS, Peak or Peak to Peak and it 50HZ or 60Hz or some other frequency.?
E

Joined Jul 18, 2013
19,461
Thank you very much, i'll dig unto that.
Some of the small commercial linear DC supplies I use also use this method.
Max.

#### Amaury

Joined Mar 17, 2019
8
hi A,
Couple more questions.
Is the 25V voltage RMS, Peak or Peak to Peak and it 50HZ or 60Hz or some other frequency.?
E
Hey E,
Peak, 50Hz.
Lemme know if i'm missing anything else

#### Hymie

Joined Mar 30, 2018
721
Configuring an op-amp (which has a 50mA max output current) as a unity gain buffer should do the job – unless someone has a simpler solution.

#### ericgibbs

Joined Jan 29, 2010
9,116
hi Amaury,
What you are asking is not a simple task.
1. A manually variable 50Hz voltage, between 0Vpk and 25Vpk.
2. A variable/fixed 25mA current limit for voltages 0Vac thru 25Vac, peak
3. A method of displaying the set voltage level.
4. A method of displaying the set current limit.

If you could explain the purpose and the way this project is going to be used, perhaps we could could suggest an easier/cheaper way of designing the project.

E