Regulating Current

Hi everyone

I know it's a very noob question, but nobody could explain me the concept clearly, and to make things worse I love electronics, but my Math is really dumb.

How can the current be regulated? I know IC's to regulate the voltage, and (as far as I know) the current depends of the load connected to the circuit. But how can the Power supply of the picture regulate its current?

(I put a link, because the picture is too big)
https://i74.photobucket.com/albums/i264/menticol/fuente/tsx3510-1.jpg


The same question applies to batteries. Another forum told me that battery chargers regulate the given current using a resistor, and its value is calculated using

V = I * R
V/I = R


I.e.: If my battery is 9 volt - 200 mA ----> 9 / 0.200 = 45 ohm?

I have the bad feeling Im making a veeery ridiculous mistake.

Thank you so much in advance

Menticol said:

Hi everyone

I know it's a very noob question, but nobody could explain me the concept clearly, and to make things worse I love electronics, but my Math is really dumb.

How can the current be regulated? I know IC's to regulate the voltage, and (as far as I know) the current depends of the load connected to the circuit. But how can the Power supply of the picture regulate its current?

(I put a link, because the picture is too big)
https://i74.photobucket.com/albums/i264/menticol/fuente/tsx3510-1.jpg


?

The same question applies to batteries. Another forum told me that battery chargers regulate the given current using a resistor, and its value is calculated using

V = I * R
V/I = R


I.e.: If my battery is 9 volt - 200 mA ----> 9 / 0.200 = 45 ohm?

I have the bad feeling Im making a veeery ridiculous mistake.

Thank you so much in advance

Click to expand...

First on your power supply question. It really doesn't 'regulate' the current but rather limits the max current based on the adjustable pot. It's to protect circuit components in case something is shorted out. If the load tries to draw more then the set max current the power supply starts to decrease it's output voltage to keep the current draw at or less then it's setting. That make sense?

On battery charging it's a little more dependent on the actual charger circuitry, but it is possible to regulate a constant current with the correct charging circuit. Ohms law is not violated by such a circuit, a constant current source will vary the output voltage to maintain the current. So voltage regulation or current regulation are both possible with the correct circuitry, just not at the same time

Lefty

Thank you Lefty, I think I got it with the power supply!

Charging is still a "black magic" for me, but I'm really interested on it after reading this https://en.wikipedia.org/wiki/Recharging_alkaline_batteries

This circuit seems to be adecuate, but relies on led colors and other variables so I don't like it too much
https://digilander.libero.it/bubblegate/ecircuit3.html

Sorry by the avalanche of noob questions that follows:

Can I simply use a LM317 variable regulator, to select a charging voltage until I read 100 mA on my Amperemeter?

**broken link removed**

Or what about a resistor on series, as I said?

V = I * R
V/I = R


If my battery is 1.5 volt - 100 mA ----> 1.5 / 0.100 = 15 ohm?
If this is correct, what should be the charging voltage, 1.5 volts?
So a 1500 mA battery coild take 15 hours charging?

Edit: To make the charger pulses, I'll use a 555 driving a transistor

Menticol said:

Thank you Lefty, I think I got it with the power supply!

Charging is still a "black magic" for me, but I'm really interested on it after reading this https://en.wikipedia.org/wiki/Recharging_alkaline_batteries

This circuit seems to be adecuate, but relies on led colors and other variables so I don't like it too much
https://digilander.libero.it/bubblegate/ecircuit3.html

Sorry by the avalanche of noob questions that follows:

Can I simply use a LM317 variable regulator, to select a charging voltage until I read 100 mA on my Amperemeter?

**broken link removed**

Or what about a resistor on series, as I said?

V = I * R
V/I = R


If my battery is 1.5 volt - 100 mA ----> 1.5 / 0.100 = 15 ohm?
If this is correct, what should be the charging voltage, 1.5 volts?
So a 1500 mA battery coild take 15 hours charging?

Edit: To make the charger pulses, I'll use a 555 driving a transistor

Click to expand...

It's not quite that easy. Yes, you can set the LM317 output voltage such that 100 ma initially flows into the battery. However as the battery accepts that charge it's own terminal voltage will gradually increase causing less current to flow into the battery. A battery is not a static resistive load but rather a dynamic load that changes with time as it charges. Charger circuits can be quite complex, some starting as a constant current and then changing to a constant voltage charger once the battery has reached fully charged. Some then maintain a steady floating trickle charge. A simple circuit as you have shown does not really deal with how to detect and act once the battery has reached 100% charge.

There are tons of battery charger circuits published on the web and you might want to research and study the different methods and features available. Simple circuits can work but you will need to understand how and when to end the charge.

Lefty

The LM317 needs to have a resistor to set the current.
Your schematic shows a voltmeter in series with the circuit. A voltmeter doesn't pass current so the circuit won't work.
The alcaline battery is not supposed to be charged anyway.

Hahaha I know Audioguru! is just a pictoric image not a schematic (I'm noob, but not sooo extremely noob)

The alkaline batteries are not supposed to be charged, for example Duracell batteries tend to leak all time. But others are well vented and keep the new given charge. And for free!

Everything you have to do is making sure of:

1. Terminal cell voltage of 1.5V
2. 100 mA charging current
3. Some kind of temperature monitoring system

Designing this for all of you is piece of cake. Meanwhile, I'll try to figure out the basics of battery chargers (Thanks again Lefty!)

Wikipedia advises not to attempt charging alkaline batteries.
They say that Duracell alkaline batteries leak when you try to charge them.
They say that Energizer's alkaline batteries heat up and do not charge.
They say that the few cells that do charge keep the new charge for only one day.
Why bother?

No, they say exotic types like Energizer's titanium batteries tend to overheat and do not charge.

The type of cells that recharge but overheat and keep the charge for one day keep expeling too much heat even out of the charger, so It's not necesary to wait one day to realize the experiment failed.

Luck or chemistry, I have seen normal Energizer batteries recharged and I'm trying to repeat the experiment with a more decent (or mayble less-indecent) charger.

By the way, the curiosity (with proper safety measures) it's a good way to learn some electronics, chemistry and waste the time. New batteries are cheap and the store is crossing the street.

Look at Energizer's datasheets. Their spec's for ordinary cheaper Energizer alkaline cells and batteries are exactly the same as for their more expensive "Titanium" cells. Even the weight and endurance are exactly the same.
The Titanium cells are a ripoff.