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LM335 to control 555 timer

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Elbobbo

New Member
Hey,
For my project I am trying to use a LM335Z to control the duty cycle of the output of a 555 timer.
So the duty cycle output of the 555 timer is 5 to 95% is this possible?
I had tried to use a thermistor to control the 555 timer to get a 5 to 95% duty cycle, with a 50% duty cycle at 25 degrees C, but to no success.
Is there any other way of gaining a PWM of 5 to 95% with a thermistor or a temperature sensor like the LM335Z?

The end goal is to output this signal to a set comparators at opposite polarity to then drive 4 MOSFETs (2 p and to n channel) in a H-Bridge with a 12vDC motor in the centre.
So the temperature dives the motor to either suck hot air in warming or draw cool are out cooling the room to 25 degrees C
Cheers
 

crutschow

Well-Known Member
Most Helpful Member
What temperatures for the 5% and 95% duty-cycles?
 

alec_t

Well-Known Member
Most Helpful Member
Controlling the 555 itself won't give you a 5% to 95% range IMO. Better to use the 555 to generate an approximate triangle wave which is then compared with a reference voltage to give the PWM signal.
 

crutschow

Well-Known Member
Most Helpful Member
Here's a 555 with a comparator to do the PWM as alec suggested.
You replace the pot at the comparator input with an amplified and offset voltage from the LM335 to get the desired variation in duty-cycle with temperature.
 
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