Can I use 5v input to get 5v output - from this circuit?

[joy123]

mod for 5 v

what mod i need to do to drive this temp controller by 5v to get 5v output?


thanks in advance

 

[cameo_2007]

Re: mod for 5 v

whats the question?
temperature controller?
hope thats a mosfet?

cud u pls clarify

 

[joy123]

mod for 5 v

sorry if i am not clear enough,
here is a
A IRFZ24N MOSFET Power transistor (N-Channel)
10K spindle trimming potentiometer
and a 10K NTC temperature sensor


i get this diagram for 12v input to get 12v output, my question is will i be able to use 5v input to get 5v output from this circuit? if not do i have to change anything(diffrent mosfet)?

 

[cameo_2007]

mod for 5 v

have you tried it?
give it a try, it will not harm your existing circuit in anyways.
and then will decide upon changing the values, and also i would advice to understand the use of those components.

here's the data sheet of that mosfet:-
http://skory.gylcomp.hu/alkatresz/irfz24n.pdf

 

[joy123]

mod for 5 v

thanks, i will try and let you know.

Added after 5 hours 8 minutes:

ok. i tryed it, only thing is i couldn't get that mosfet, so got IRF540 mosfet, data sheet is **broken link removed**

but its not working, how can i check where is the problem?

 

[cameo_2007]

try these:-
Remove the potentiometer and NTC and check,
or remove the potentiometer, adn replace the NTC with a 1K resistor and check,

What is the drain current going to be?
If the voltage is limited to 5V, you can go for a transistor instead of Mosfet.

 

[joy123]

the drain current going to be 5v 150ma, i will try that and let you know,
can you give me a idea what kind of transistor i can use instead mosfet?


thanks for helping me out.

 

[joy123]

If i disconnect ntc sensor its works, fan start spinning continues. Is that mean thats sensor causing problem? There is no ntc sensor in maplin to check if its faulty.

 

[cameo_2007]

not that the NTC is faulty, its just that the value will not match the reduction in voltage , ie 12V to 5V

It doesnt matter if you remove it, or you can try with a lower value, say 5K

 

[joy123]

It doesnt matter if you remove it

do you mean it doesn't matter if i remove the ntc, it will be still act like temp controller? sorry i lost you here!

 

[keith1200rs]

If you remove the NTC with the pot still there and the fan turns then you have it wired incorrectly. Removing the NTC should guarantee the fan will never run.

The circuit is very poor in the first place. The IRF540 is not a good choice for 5V operation in that circuit - the threshold can be 4V. A 100V 33A MOSFET isn;t the best choice for a 5V system.

Still, check your wiring. Then you may have to increase the pot value to get it to work (maybe 50K or 100k).

Keith.

 

[joy123]

I m kinda confuse, from my understanding ntc decide whether to send volt or not! So if i remove the ntc it suppose so spin, isn't it? Now i don know how pot works, but i checked the wiring. And its looks ok. I m gonna try with diffrent pot and lower value ntc today and let u know.

 

[keith1200rs]

No. The gate og the MOSFET needs to be positive to turn on. The MOSFET needs to turn on to turn the motor on. The only way the gate of the MOSFET can be positive is if the NTC is connected. The pot to ground then forms a potential divider so the voltage on the gate will not be enough to turn on the transistor at low temperatures. As the temperature rise, the NTC resistance drops which will increase the voltage on the gate and turn the MOSFET on.

So, without the NTC, the transistor will never turn on, assuming you have the pot in place. If you remove both, the gate of the MOSFET will be floating,so anything could happen! If you have the NTC in place and remove the pot, the motor should run all the time.

Keith.

 

[joy123]

thanks guys , its finally working as it should be, i changed the pot, still using 10k NTC and the same mosfet. working perfect now.

 

[cameo_2007]

infact i realised the pproblem now only.
pardon me, if i have mislead you.

its nothing but the threshold to trigger the MOSFET has changed when you reduced the voltage from 12V to 5V and it didnt work.

And the threshold is set by the pot and i guess it worked now because of that.

The moron in me was assuming the NTC was used as an inrush current limiter.

 

[keith1200rs]

I'm still puzzled how it turned on with the NTC removed! Still it sounds like it works now anyway.

Keith

 

[cameo_2007]

Keith, i assume the NTC was removed, but the circuit was still closed, ie, the 5V was directly given to the Gate.

 

[joy123]

yes cameon , you are right the circuit was closed. i am using now 10k NTC with 22-Turn Cermet 50k with the same mosfet.

 

[keith1200rs]

Keith, i assume the NTC was removed, but the circuit was still closed, ie, the 5V was directly given to the Gate.

I would describe that as the NTC being shorted. 'Removed' means it would be open circuit.

Keith