[Joshua Flynn]

I have a handcrank unit that can produce voltages varying from 0.1 to 5.7 volts (5.7 seems to be the ceiling), with an average range of about 4.8 to 5.7 volts.

What component(s) would I have to buy, and what shop would I get it from (as I'm in the UK) in order to stablise voltage levels to within about 4.9v to 5.1v?


For context, I am operating a raspberry pi which cannot handle voltage loads beyond 5.1v (I'd assume a +/- .1 volt tolerance over 5 volts hence 4.9v - 5.1v), so the voltage variation cannot be outside the .1 volt bounds (or I risk damaging the pi permanently).

[smoothy]

You can clamp it at a certain level or you can regulate it to that level...

You also need something to store a charge being either a large capacitor or bank of them... or a battery...

You have a number of options... and the two I mentioned aren't the only viable ones.

[Joshua Flynn]

What components would I specifically be looking for? I know capacitors have different classifications and I wouldn't know which one to look for that would be suitable for the 5v.

Voltage regulators of 5v require usually a higher voltage (usually something about 7 volts) to get 5v stable output (5.7v is ceiling), for example, the 7805 requires 7 volts input http://en.wikipedia.org/wiki/78xx . Could you tell me more about how I would clamp the voltage?

[smoothy]

Here is a easy to understand explanation on how to use a zener diode as a regulator.

Zener Diode Shunt Regulator

There are 4 pages so click through them.

With capacitors you pick one in a voltage rating larger than you are using... they will smooth out voltagefluctuations as well... so they will be an important part of any solution.

Consider a capcitor in this use like a very very low capacity battery... though your standard calculations will be important.

[Joshua Flynn]

Here is a easy to understand explanation on how to use a zener diode as a regulator.

Zener Diode Shunt Regulator

There are 4 pages so click through them.

With capacitors you pick one in a voltage rating larger than you are using....they will smooth out voltagefluctuations as well....so they will be an important part of any solution.

Consider a capcitor in this use like a very very low capacity battery.....though your standard calculations will be important.

So just to clarify, if the circuit goes: Handcrank 5.7v -> capacitor -> 5.1 zener diode -> output, the output would be 5.1v, with any excess (.6v) being removed by the zener?

What sort of capacitance size would give me roughly 30 seconds worth of ~5v?

[smoothy]

So just to clarify, if the circuit goes: Handcrank 5.7v -> capacitor -> 5.1 zener diode -> output, the output would be 5.1v, with any excess (.6v) being removed by the zener?

What sort of capacitance size would give me roughly 30 seconds worth of ~5v?

IT takes more than a single component... and if you are needig 30 seconds of power... without craniking... you want a small recargible battery... as that's a tall order for simple capacitors to fulfill. Even taking a wild guess what that Rasbery pi draws... which may not be a lot... but it is if you use a bank of capacitors to carry the load that long.

[Joshua Flynn]

IT takes more than a single component.....and if you are needig 30 seconds of power...without craniking....you want a small recargible battery.....as thats a tall order for simple capacitors to fullfill. Even taking a wild guess what that Rasbery pi draws....which may not be a lot...but it is if you use a bank of capacitors to carry the load that long.

Okay, just exploring options (thank you for the help so far).

I'm confused about the zener diode after looking into it. Does it ensure voltage is at a minimum 5.1 volts (which means it can range from 5.1 to 5.7v variable?) or does it incap voltage over 5.1 volts to just 5.1 volts?