When the red alarm LED is lighting, eliminate the overcurrent factors, it will automatic reset (automatic mode), or push the Reset Button, reset the power (Manual Mode).

That appears to act as a resettable fuse.
I think the TS wants a constant-current limiter, not a fuse.

 

hi quasi.
Look at this possible option.
You will have to manually set the V/I output required.

E
https://www.ebay.co.uk/itm/224104305409?hash=item342da85301:g:NnMAAOSwSe5b7tqe&amdata=enc:AQAHAAAAwKKgH2ohpMo1ys8nkRLNjEpftA7xlIf5zAhqfK146ey0GBzdOQUWTREeMeiCnrtvAovA/IMvseqI02/DA0PJWEXlL+uAw7gd6z8fbAdh+elQ/KmI3UnMIRfxHBBEq4a/Xj2ogLiI1FzKMmTWIyeq88ldyYwPOVkM175mvRkE7CtCd5Bc1C+B5YAeU5PX4K9oeIufERGmMw0LTRSTxO6uFUzugN7H5gMNaK3K6dfXsc+ot5mrKDXrkLaoP0t1vOI18g==|tkp:Bk9SR5j2hIWQYQ
View attachment 280816

Thank you ericgibbs. I think this is what might do the job of controlling the current. The only concern is that I need to try it and check. Papabravo mentioned something that if the current is limited the voltage will be reduced. But what I was thinking is that I can fix both.

 

Thank you all for all the information. As an ignorant in the subject, I learned a lot just from this thread.

The options provided by ericgibbs and Danko are the closest thing to what I'm looking for. I also found a more accurate and higher power device but it is way more expensive.

https://www.amazon.com/dp/B09SWKJNDQ?psc=1&ref=ppx_yo2ov_dt_b_product_details

What I will try to do is:

if I have a load that can take 10A at 12V, I will use one of the suggested devices to limit the current at 2A and increase gradually 1A at a time. I hope this will not impact the voltage value as I still need the voltage to be fixed at 12V. I'm not sure if this adheres to or defies Ohm's law. But I'm under the impression that playing with resistance could allow for this to be achieved. Again, I could be totally saying non-sense. But I will experiment with one of these devices and will definitely gain more insights on this.

 

Voltage and resistance are friends on a teeter-totter. As one goes up the other goes down. You can't set both ends of the teeter-totter higher without changing the balance point. The current is the center point of the totter.

In electronics you have three basic things: Voltage, Current and Resistance. (there's a lot more than just three basic things, but for this discussion we'll just consider these three) At a certain voltage and a certain resistance the current will be what it will be. For instance; 10 volts and 10 ohms means you will see 1 amp flowing through the circuit. If you want 2 amps then the voltage has to go up to 20 volts. The resistance isn't going to change. If your circuit wants to draw 1 amp but you want to limit it to 1/2 amp (0.5A or 500mA) then the voltage MUST go down. So you can't set a current limit AND a certain voltage. You get one or the other. The only other way to change the amperage is to change the resistance. Lower resistance will equate to higher current and higher resistance will equate to lower current.

What I'm picking up in this thread is the TS wants 12 volts for his project. At the same time he wants to insure the current never goes above a set limit. Let's assume the desired limit for current is 2 amps. As his electrolus solution changes in conductivity the current will change. Likely with more contaminants in the solution the resistance will go down and thus increase the amount of current being drawn. It's when the current exceeds the desired 2 amps (this example) the TS wants the current limited. In this case the voltage will have to be dropped from 12 volts down to whatever voltage and resistance dictates and meets the 2 amp setting.

So you CAN set a current, but most power supplies (not batteries) will increase the voltage in order to maintain the current. As the resistance drops the voltage will be dropped to maintain the current. You can't have both. Now, a car battery can't deliver 20 volts if the set current demands it. What I think you want isn't a constant current but rather a current limit - just as your title describes "Current limiting device". But in this case a fuse wouldn't "Limit" current it will shut down the circuit if the limit is exceeded.

Now, I don't know if there's a circuit that is designed to prevent current from exceeding a set limit but I bet there is. I just don't know of one. I might imagine a comparator or op-amp that monitors current. When it goes above a limit it will drop the voltage in order to maintain the max set current.

Lately I'm becoming more of a cabinet maker than an electronics hobbiest. Good luck. I'm sure someone can address your needs. The guys and girls here are pretty darn sharp. Me? I'm as sharp as a fuzzy tennis ball.

 

I also found a more accurate and higher power device but it is way more expensive.

How about this one.

limit the current at 2A and increase gradually 1A at a time. I hope this will not impact the voltage value as I still need the voltage to be fixed at 12V. I'm not sure if this adheres to or defies Ohm's law.

Ohm's law (V = I * R) shows that, to maintain a constant voltage as the current changes, the load resistance must change in inverse proportion to the current.

 

How about this one.
Ohm's law (V = I * R) shows that, to maintain a constant voltage as the current changes, the load resistance must change in inverse proportion to the current.

Thanks, this indeed a much cheaper and practical one.

 

Voltage and resistance are friends on a teeter-totter. As one goes up the other goes down. You can't set both ends of the teeter-totter higher without changing the balance point. The current is the center point of the totter.

In electronics you have three basic things: Voltage, Current and Resistance. (there's a lot more than just three basic things, but for this discussion we'll just consider these three) At a certain voltage and a certain resistance the current will be what it will be. For instance; 10 volts and 10 ohms means you will see 1 amp flowing through the circuit. If you want 2 amps then the voltage has to go up to 20 volts. The resistance isn't going to change. If your circuit wants to draw 1 amp but you want to limit it to 1/2 amp (0.5A or 500mA) then the voltage MUST go down. So you can't set a current limit AND a certain voltage. You get one or the other. The only other way to change the amperage is to change the resistance. Lower resistance will equate to higher current and higher resistance will equate to lower current.

What I'm picking up in this thread is the TS wants 12 volts for his project. At the same time he wants to insure the current never goes above a set limit. Let's assume the desired limit for current is 2 amps. As his electrolus solution changes in conductivity the current will change. Likely with more contaminants in the solution the resistance will go down and thus increase the amount of current being drawn. It's when the current exceeds the desired 2 amps (this example) the TS wants the current limited. In this case the voltage will have to be dropped from 12 volts down to whatever voltage and resistance dictates and meets the 2 amp setting.

So you CAN set a current, but most power supplies (not batteries) will increase the voltage in order to maintain the current. As the resistance drops the voltage will be dropped to maintain the current. You can't have both. Now, a car battery can't deliver 20 volts if the set current demands it. What I think you want isn't a constant current but rather a current limit - just as your title describes "Current limiting device". But in this case a fuse wouldn't "Limit" current it will shut down the circuit if the limit is exceeded.

Now, I don't know if there's a circuit that is designed to prevent current from exceeding a set limit but I bet there is. I just don't know of one. I might imagine a comparator or op-amp that monitors current. When it goes above a limit it will drop the voltage in order to maintain the max set current.

Lately I'm becoming more of a cabinet maker than an electronics hobbiest. Good luck. I'm sure someone can address your needs. The guys and girls here are pretty darn sharp. Me? I'm as sharp as a fuzzy tennis ball.

Thank you very much Tony, this is very informative and educational.

 

One last question and then I will quit digging into the subject.

If the load is allowing 2A at 12V. This means that the resistance of the load is 6 ohm.

Now, if the resistance of the load drops to 4 ohm, it will allow 3A to flow at the same voltage (12V).

What I'm imagining is that if I want to maintain 12V and 2A, a potentiometer can be used to make up the difference in resistance which is adding an additional 2 ohms to the load to keep it at the initial load value (6 ohm).

Is this a valid assumption?

 

What I'm imagining is that if I want to maintain 12V and 2A, a potentiometer can be used to make up the difference in resistance which is adding an additional 2 ohms to the load to keep it at the initial load value (6 ohm).

Is this a valid assumption?

Yes, that is correct, but why do you want to keep the voltage at 12V if the load voltage is less?
That is just wasting power in the added resistance.
Note that you will need a power rheostat, not a potentiometer, since the power dissipated in the rheostat will be 8W, for 2A through 2 ohms.

 

Now, if the resistance of the load drops to 4 ohm, it will allow 3A to flow at the same voltage (12V).

What I'm imagining is that if I want to maintain 12V and 2A, a potentiometer can be used to make up the difference in resistance which is adding an additional 2 ohms to the load to keep it at the initial load value (6 ohm).

The voltage across the 6 ohms (4+2) is 12 volts. The voltage across the load is 8 volts.

 

Hello,

Is there a ready made device that can be used to limit the current being consumed by any load. Specifically, I would like to limit the current going out from a car battery for a home project. I'm looking for something that is adjustable where I can select what is the maximum current that can be withdrawn from the battery.

I appreciate your help.

Best Regards,
Tariq

Yes, it's called a 'LOAD'. LOADs draw only the current they are designed to draw at a given voltage.

 

Yes, that is correct, but why do you want to keep the voltage at 12V if the load voltage is less?
That is just wasting power in the added resistance.
Note that you will need a power rheostat, not a potentiometer, since the power dissipated in the rheostat will be 8W, for 2A through 2 ohms.

Thanks, that clarify things. It looks I have a major gap in the fundamentals. But thank you for being patient with me.

 

The voltage across the 6 ohms (4+2) is 12 volts. The voltage across the load is 8 volts.

Thanks. It is clear now to me.