# Regulate, convert to DC and store current from home made AC generator to charge laptop

I am working on a small experimental project, learning more and more about electricity and electronics.

So, I have found this broken mixer and, surprisingly, it has a 300W engine with magnets that produces current when rotated. Just what I needed.

Now, what I intend to do is make it capable of charging a laptop battery, at least. The laptop's charger

• needs 100 V ~ 200 V and 1.6 A (50 ~ 60 Hz) AC and
• outputs 19 V and 4.5 A DC.

Now, I need to take some decisions and understand several things better

1. First, I need to decide if I should make my generator output at least 100V and provide at least 1.6 A to the laptop's charger then let the charger take care of the battery. Looks like the simplest and most secure solution. But if the generator creates 19 V and 4.5 A and sends this directly to the laptop, less work is necessary to rotate it, I guess. Why would I produce high voltage then have the charger reduce it?

2. No matter, what option is better, I need to know: how to regulate the current, how to transform the voltage as needed, how to store it temporarily, at least to keep it steady.

3. I have read a little bit about diodes, Zener diodes, regulators, induction coils, transformers and capacitors. Now, I have to find out how and in which order to connect these (I have bunches of them, of all sizes and colors) in order to achieve something like what I want.

So, what should I do?

• Convert the AC current to DC using a diode bridge, and add a smoothing capacitor
• Regulate it with a Zener diode (and required resistors to limit current flow) or a regulator (preferably to 12 V)
• Convert the voltage from the regulated one to 19 V then use a capacitor to keep the amount if energy steady and provide it to the charger / battery?

or maybe

• Use a regulator to stabilize the AC current
• Convert the voltage to 100 V and use a capacitor to store it

Maybe this looks like I am asking for a circuit scheme (which would help, too) but I also want to understand every step

• You need to start with specs, you have defined the load, but have no specs for the source, so either find a datasheet or characterize the generators I-V for different dummy loads. Commented Jul 2, 2017 at 18:19

This would be an interesting project to learn some electronics but it may not be a practical one. For example, you don't say how you will power your generator.

First understand that your laptop power supply's relationship between power in and power out is given by

Power in = power out + losses


If you have a good power supply the losses will be about 10 - 20%.

You should also know that $P = VI$ so that your PSU can output $P = 19 \times 4.5 = 85\; W$. If it were 85% efficient it would draw 100 W from the mains. At 100 V this would be 1 A. At 200 V it would be 0.5 A. The 1.6 A figure is worst case surge on power up.

1a. First, I need to decide if I should make my generator output at least 100V and provide at least 1.6 A to the laptop's charger then let the charger take care of the battery.

If I had to do it this is the way I would do it. The PSU regulator offers some protection to the laptop.

1b. But if the generator creates 19 V and 4.5 A and sends this directly to the laptop, less work is necessary to rotate it, I guess.

It would, in theory, be 15% less because you wouldn't have the losses of the PSU. This would probably be replaced by the losses in your new circuit.

1c. Why would I produce high voltage then have the charger reduce it?

Because your mixer windings are rated for $I = \frac {P}{V} = \frac {300}{230} = 1.3 \; A$. They won't supply 4.5 A. (I have assumed you live in 230 V territory. You didn't add that information to your post or your profile.)

1. I need to know: how to regulate the current, how to transform the voltage as needed, how to store it temporarily, at least to keep it steady.

Yes you do. And you will need to research this rather than hope someone here is going to design it for you.

[Should I] convert the AC current to DC using a diode bridge, and add a smoothing capacitor.

If you want DC or a switched mode power supply this is essential unless you are generating DC.

Regulate it with a Zener diode (and required resistors to limit current flow) or a regulator (preferably to 12 V).

This would be a hopeless way of regulating. It is not used in commercial designs as it is inefficient and regulation is poor.

Convert the voltage from the regulated one to 19 V then use a capacitor to keep the amount if energy steady and provide it to the charger / battery?

You need to study SMPS power supply design. Your question implies that you don't understand enough to start this project yet.

Cautions

The risk of injury are high if you use voltages over 100 V.

You have to factor in the risk of destroying a laptop if you get something wrong.

I suggest you use the generator to power some LED strips instead. If they blow you've lost €10.

• I will start researching on new things I see I have to learn, while playing with low voltages to learn more about AC to DC, regulating potential and storing charge. Thanks for the explanations
– ali
Commented Jul 2, 2017 at 18:59