Is it possible for me to swap a NE555 timer chip with a cmos LM7555 timer chip? From what I know cmos LM7555 timer chip uses less power so I want to swap it.

https://www.jaycar.com.au/5a-12vdc-pwm-motor-speed-controller-kit/p/KD6102

Above uses the NE555 chip and I would like to replace it with a cmos LM7555 chip as below

https://www.jaycar.com.au/lm7555-cmos-timer-ic/p/ZL3455

Will that work?

 

hi happirt,
A problem maybe the input current requirement of the circuit driven by the 555.
The 555 TTL max Iout is approx 100mA to 200mA , the CMOS version is limited approx 5mA or so.

Do you have copy of the circuit of the module you have linked.
E

 

I think this is it

https://www.picclickimg.com/00/s/MT...ed-Control-HHO-PWM-electronic-circuit-_57.jpg

 

hi,
The layout of the components are different in the link modules, the two circuits do not match.

 

Sorry, this is the one

https://diyodemag.com/_images/5a8bb4a6c672e0a73df42bcf

https://diyodemag.com/projects/choppy_the_pwm_maker

 

hi,
The 555 pin #3 Out is driving a Resistor/LED, also the IRF540 Gate.
Looking a the component values for the LED and Gate I would say a CMOS 555 would not be suitable.
The LED is drawing more current from pin #3, than a CMOS could supply.

E

 

Thanks for your expertise.

What if I was to leave the led out? could the 7555 supply the IRF540 gate?

 

hi,
Looking at the IRF540 datasheet, I would suggest you could try it without the LED.
On a low current load test, monitor the temperature of the IRF.

Are 555 unavailable in your area.?

E

 

Hello,

@ericgibbs , Where did you find the 5 mA output current?
I only can find an absolute maximum output current of 100 mA in the Intersil datasheet if the icm7555, wich is a cmos version of the LM555.

Bertus

 

hi,
The TLC555 Vhigh output, which is required for Gate drive, from the d/s is listed as this image., for Vdd =15v
E



EDIT:
This is for a ICM7555

 

Hello,

@ericgibbs , Ah, I see. The sourcing current is much lower as the sinking current:


Taken from the LMC555 datasheet.

Bertus

 

@bertus.
I have suggested to the TS that he tries his CMOS 555 [ without driving the LED] , he may just get the result he needs.
Hope he comes back and posts his findings.

E

 

I have updated the diagram, hoping someone can help me...



I think the problem is the green ground connection, I'm not sure where to connect to for it to work?

 

hi,
Do have any technical data for the fan or a link you could post.?
E

 

This is the fan
https://www.silverstonetek.com/product.php?pid=711&area=en