# how to create a voltage limiter circuit

hello to everyone,

i am trying to regulate a voltage less than 5V the input voltage is 0 - 15V around.

Except the voltage regulator, are there any methods that could regulate the voltage below 5V

like a valve that exceed the limiting flow, then the valve will open for the excessive flow to flow to another places.

are you looking for a booster circut?

are you looking for something to keep one specific voltage regulator?

are you looking for a voltage divider (as in are you trying to use an arduino to read voltages between 0 and 15 volts)?

ike a valve that exceed the limiting flow, then the valve will open for the excessive flow to flow to another places.

That idea sounds like a shunt regulator using a zenner diode.

http://ecelab.com/circuit-stabilizer-shunt.htm

It wastes current though and the zenner burns off the excess current

Thanks

i have a question with this circuit below

for the other side of the resistor, there is a power needed ? i could not just use the zener diode, when there is above 5V, the zener diode will allow the current to flow to another load, that regulating the voltage?

Sorry that question just does not make any sense could you try again please.

umm
for the zener diode
when it reached 5V , the zener diode wil open the door to let the current flow

------->
direction of current

--------->

which installation of the zener diode is correct ?

pls forgive me for the bad presentation of circuit

Sorry still don't understand.

On the picture you posted the input voltage is on the left marked Vin the output voltage is on the right marked Vout, this is connected to the load. If the voltage on the zenner exceeds the 'zenner breakdown voltage' it conducts or shunts away the excess current through the diode and stops the voltage rising. This means the voltage on the load never exceeds the 'zenner breakdown voltage'. This is an alternative way to control voltage without using a voltage regulator which I though is what you asked.

but, then there are two Vin then ?

WOW, Richard, it is incredible my situation is , there is a sensor that have a output voltage about 0-20V and after the transformer, it dropped to around 0 - 6 or 7V but the arduino could not take more than 5V, that's why i need a zener diode to regulate the voltage, in case of excessive voltage entering.

Which mean, the load would be the arduino.

i have a question, if the zener diode is opened for excessive voltage to flow, there is not needed another load for the excessive voltage to consume ? just connect to the ground ?

And here is another method that i searched but i don't know about this, which is a transistor

Could a transistor to limit the input voltage at 5V ?

If I understand you correctly :- you have a signal source that you wish to act as an input to the arduino. The signal can vary from 0 up to 7 volts or maybe higher. You want a saferty circuit to stop the signal from exceeding the arduino input limit of 5 volts.

Is this interpretation correct ?

OK if so you need a simple divider to drop the 0 - 7volts down to 0 - 5 volts then a safety feature to ensure it never exceeds 5 volts.

Place 2 resistors in series made up of a 390ohm and a 1000ohm. The junction of the two is the input to the arduino. The free end of the 390 goes to your signal and the free end of the 1000 goes to the common ground (of both signal and arduino. Now connect a 5 volt zener between the arduino input and the signal ground.

The arduino input will now read 1000/1390 or 71.9% of the signal, which, if it is 7 volts will be 5 volts, (5.03 actually if all resistor values are exact - which they won't be) with 5ma being drawn from the source (7/1390)

In excess of 5 volts the zener will start to conduct so passing more current through the 390 ohm resistor and increasing the voltage drop across it. The current through the 1000 ohm resistor remains constant at 5ma.

This will work but be aware that the measurement is only linear up to a signal level of 7 volts, after which it saturates and remains constant until the signal once more drops below 7 volts.

jack

At some point you should just give up and ignore them and let them fumble in the dark. There are enough examples of properly asked questions here that a few minutes of their time would have taught them how to ask for help.