Would someone know and be willing to share
knowledge of how such can be accomplished
If the current is variating, it’s not DC.
But, if you want constant voltage regulation, that sounds like a job for a linear regulator like the LM1117.
I think a battery can do this, and maybe a capacitor could as well*
The most common and used application for smoothing capacitors is after a power supply voltage or a rectifier.
What I am after, is an excersise bicycle that has two car´s power generators
connected to flywheel and somehow leaded to laptop. So basicly self powering
laptop at rural place or in household if you want to save energy or pollution.
LM1117 sounds good but voltage needed is 19.5
Maybe I just got to do an rig with arduino that
changes the greater voltage based on lets say
bicycle lamp generator voltage
constant speed by mechanics would be awesome
just charge a battery with the generators or alternators and run the pc off the battery, it acts as a buffer.
also this way you could work out and then watch a movie after,
beware, it takes quite a bit of peddling to generate a sizable amount of power.
This is tricky due to the large amounts of energy you need to store. For smaller amounts of energy, a few large capacitors would be enough, but when you want to power a laptop you’d probably need a decently sized battery, which is definitely not cheap - the cheapest option would be a lead-acid-based battery.
However, there are a few challenges there - you’ll probably need a buck-boost-configuration regulator IC to keep your constant voltage, along with a charging control IC to generate the appropriate charge curve for the battery.
If this is your first project regarding power management and battery stuff, it’s probably too complex tbh.
@BluePrintRandom Charging a car battery inside household can generate lethal gasses.
Otherwise two car batteries and resistor would sound good to me.
@lukasstockner97 You are right, this is something too complex for me. Few large capacitors…
got to keep in mind though.
I would be willing to invest on this because I think its worth it. There seems to be many of these
projects on web but maybe not a package that has the full toy, station, aparatus what ever you name it.
Using two alternators would mean having voltage regulators; because almost all of them are internally regulated. The issue is each would be regulated at 12v give or take; and they would be likely to damage each other, if they are on the same circuit. This could however be solved with diodes. It’s still a bad idea though.
It might be best to use a single alternator and two batteries. That way the output would still be 24 ish volts that could then be adjusted with some simple components. I guess you could use two alternators but it becomes quite a bit more complex; and would probably require some testing.
bus alternator generates 24v
Hmpf. There is a lot more work in this than you realise. Electronics is simple and easy until you figure out what it’s actually about. An LM1117 will not provide the current required for a laptop. It would probably catch fire, as would most linear regulators at the power level of a computer (if you have a significant voltage drop). Also, a linear regulator turns excess energy into heat, and so is dismally inefficient in a lot of cases. (And in this case, that extra heat going out the regulator is coming from your legs)
My laptop’s power supply is 65W at 19V. The good news is that cycling at 15kmph is also about 60W, so you can actually do it without needing to be putting tonnes of effort into the cycling.
So what will you need? You’ll need a cycle of some sort, and a generator of some sort. Then you’ll need a switchmode power supply. I used this module to power a computer on board an agricultural robot several weeks back, and they’ve worked well. You will need a board to mount it on and a voltage setting resistor and some pretty large value MLCC caps to get a stable output voltage. The information’s there in the datasheet… That regulator is a buck converter, and assumes you need a lower output voltage than input voltage, so you’d need 24V input to get 19V output. If you’re only getting 12V out of your alternator, you’ll need a boost converter, which are often harder to find/more expensive. I’d recommend just using an alternator that gives you 24V.
Not necessarily. The load can change causing varying amounts of current draw. DC is direct current, in one direction.
Again alternators are internally regulated. The old generators are not; but more modern alternators are. That however is not the issue for running the laptop. With two batteries as the pool, the output voltage, and amperage can be adjusted on a breadboard with simple components. There won’t be heat issues or anything of the sort provided that the batteries are not overcharged.
BTW I wouldn’t use car batteries. I would use marine batteries. They are made support lengthy and less demanding draws.
Typically, the terms are defined in terms of frequency, where DC means the constant component.
Therefore, no DC component => mean of zero, aka “normal” alternating current
In case of varying amounts of current draw, you have your “DC offset” around which the current is fluctuating.
So, pure DC indeed implies a constant current/voltage.
@sdfgeoff - Yep, for this power range, a linear regulator is definitely a no-go.
I’d imagine that the problem with the bike solution is how stable the incoming voltage from the generator is - assuming that it’ll stay over the laptop voltage is a bit optimistic.
For a nice continuous supply (which should be the goal, I don’t expect laptops to be happy with a charging current that switches on/off once every second), you’d most likely need a combined buck-boost-converter.
However, of course, a boost converter isn’t going to magically summon the power - it will just draw more current, which the generator might not be able to supply.
That’s where I see the main problem - the power output from the bike is going to fluctuate with every “leg cycle” (sorry, no clue how to call it), so you’ll need some serious smoothing on the input - at the power and time scale we’re talking about here, a small supercap bank should do the job - Farnell has 6V 5F supercaps, putting 4 in series will give you enough voltage range, and putting two such banks in parallel should give enough capacitance to keep up for about 1-2 seconds while staying in the buck-boost’s operating range. Of course, that needs control circuitry to protect the caps from overvoltage.
Edit: Of course you could always go for the low-tech smoothing by attaching the bike to a decently-sized flywheel.
The only thing that the alternator would be used for is charging the batteries. There is no doubt that an alternator can do so; even when the laptop is running, as this is observed in modern vehicles. An alternator can go above and beyond what is needed provided that the RPMs are sufficient.
The two batteries provides storage for the voltage; that would then be transferred to the laptop. The alternator is designed to charge the batteries and internally regulated. The batteries would also function as a buffer between the alternator and the converter. What is really needed is converter after the fact; to ensure that the proper voltage and amperage are going to the laptop.
Alternator ----> two batteries in parallel ----> converter -----> laptop
That should work in theory.
I have done it with a laptop and a 12 volt battery stack of deep cycle rv batteries we charged with a generator,
(my dad was sick and wanted to live traveling tbe country in a rv so I became his driver)
we used it to watch dvd and I used to play tremulous 
in theory the generator, and alternator are kinda the same animal if they spit out 12 volt,
(used laptop 12 v travel charger to charge laptop off battery stack)
Thanks dudes.
But if voltage is going to battery, what will the battery give out, is it what is in battery or what is keeping loaded hear, I know I am naive, but I honestly do not know this.
However how I would get my system done is with arduino kit that alters the voltage based on input. Assuming here generator would be alllways above the needed voltage. However I do not undertand amps, oh know…
the offtheshelf converter takes lot of the charge it seems
It might be more economical to use a solar panel. Both the users work load, and also cost of parts. A 100 watt 12 volt solar panel should give you enough power for a 'basic laptop. This will work best if put inside a battery. It should be able to work without the usage of a battery.
What you will need with the battery or solar panel is a power converter. Not inverter, converter. The power converter depends on the laptop’s wattage. I assume the laptop is 120volt input, that runs on about 50watts of power.
You should also look at wind power. You should be able to make your own if you can.
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