please could you help?
i need a circuit that will block voltage lower than 5V
is there a specific component for this or will i need to build a sub-circuit?

It's a circuit that runs from a dynamo on a push bike.
Obviously the dynamo will take a second or two to get up to 6+ volts.
But my circuit only works when the voltage is above 5V because the device doesn't accept it at first you have to plug it in when you’re moving which can be a bit dodgy.

 

Look at...
http://ww1.microchip.com/downloads/en/appnotes/00779a.pdf

Turns off (or waits to turn on) when under voltage condition occurs.

 

hi,

7805 DC regulator might help, it usually gives solid 5V output for greater input voltages from 7 - 20V, i think it will block voltages below 5V. got to try though let me know

happy testing

BR

 

7805 DC regulator might help, it usually gives solid 5V output for greater input voltages from 7 - 20V, i think it will block voltages below 5V. got to try though let me know

I've tried it, it doesn't do that. It very sloppily follows the input minus a volt or three till it reaches 5V.

 

Please be more specific. Instead of saying it is a circuit - tell us what the circuit is meant to do. It matters.

If you want to run 500 LEDs for a custom illumination system or if you want to run a small LCD display readout of an accelerometer/speedometer, those are two different examples we might guess and they would involve different power requirements.

Battery backup power with an isolation diode from the dynamo is the simplest system.
It depends on what you need.