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need 555 circuit falling to 0.3v

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partam

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Need a 555 timer circuit that switches between 0.33 to 0.66 V
I built one from 0V to 0.8V but it's not what i need.

As for the time for T1 and T2 we can always arrage with R1 R2 and C

Thanks
 

Re: 555 circuit but falling not to 0V

What load are you driving?
How much current do it need to produce?
Does it need to sink or source current?
What accuracy do you need on the voltage levels?
 

Re: 555 circuit but falling not to 0V

If you can try several 555 timers and select one with the lowest output voltage ..

According to the 555's data sheet(s) the output "L" voltage should be below 0.1 (mav 0.25V) for 10mA load but can rise to 2V (max 2.5V) for >100mA load ..

Regards,
IanP
 

Re: 555 circuit but falling not to 0V

The higher 0.6 volts is not a problem
The problem is the 555 timer switches between 0.6 and 0 volts
What i want is switching between 0.6 and 0.3 volts
 

Re: 555 circuit but falling not to 0V

I thought you were concerned that the 555's output didn't go as low as 0V ..
The "subject" of you post didn't reflect clearly what you had been trying to achieve ..

If you would like to "shift" the "L" level to 0.3V you may consider connecting 555's GROUND pin to 0V through a Schottky diode ..
For example, the 1N5821 Vf voltage is somewhere around 0.3V ..

Regards,
IanP
 

Re: 555 circuit but falling not to 0V

http://www.mkiv.com/techarticles/oxygen_sensor_simulator/o2sim.png

This is the graph but instead i need 0.3 volts as the L level.
Will try tomorrow the Schottky diode .

Thanks
 

Tried the Schottky diode ...didn't work

Put one way doesn't make any difference
Put the other way the 555 timer stops working and goes on all the way.
 

Do it like this. You need a regulator to get stable output voltages, and you can use a CMOS 555, whose output swings rail-to-rail.
 

Thanks for your suggestion.

What happens if i don't use the voltage regulator?
If it's a small voltage swing on the output...it's ok.
 

partam said:
Thanks for your suggestion.

What happens if i don't use the voltage regulator?
If it's a small voltage swing on the output...it's ok.
Click to expand...
This should work. Be aware that positive spikes on the supply (which are common in automotive systems) will get rectified by D1 and C2, causing your output voltage to "jump" when one occurs. This may not be a problem.
Also - the LED that was removed (D2) would have been so dim as to be useless. You can add a separate resistor and series LED from pin 3 to GND if you want.
 

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    partam

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