Can someone simulate this diagram for me please

[john2k]

I came across the following diagram on the internet which is suposed to simulate the exact waveform a post catalytic convertor o2 sensor in a car does. I'm not too savy with this stuff and wanted to know if anyone is able to run a simulation of this exact diagram and show me how the output measures as a waveform over a period of time?

One thing I don't understand is usually a LED has a resistor before it, so how is that first LED receiving full voltage and not blowing?

Thank you.

Here's the diagram below:

 

[john2k]

I think i've managed to create this diagram on LTSpice but i'm not sure how to run a monitor to monitor the output as a graph. If i click the man icon and type 1 in the stop time and then put cursor over the output i get about 970mV. I've uploaded the LTSpice file i created if anyone can help. Thanks

 

[Alec_t]

so how is that first LED receiving full voltage and not blowing?

Apart from an initial 0.5mS or so duration start-up current peak of ~700mA while the 22uF cap charges, the top LED passes only a few mA required mainly by the 555.
Here's my simulation output. The voltage is dependent somewhat on the forward voltage drop of the particular LEDs used.


Note: My sim time is 30S, not 1S .

 

[john2k]

Apart from an initial 0.5mS or so duration start-up current peak of ~700mA while the 22uF cap charges, the top LED passes only a few mA required mainly by the 555.
Here's my simulation output. The voltage is dependent somewhat on the forward voltage drop of the particular LEDs used.
View attachment 48664

Note: My sim time is 30S, not 1S .

Thank you, the LED's suggested for this is 1.7V@20mA

 

[john2k]

The voltage is dependent somewhat on the forward voltage drop of the particular LEDs used.

What LED spec did you use to simulate getting 0.6V? in LTSpice i cannot seem to be able to add a 1.7V 20mA LED .

 

[Ylli]

Try this, add a spice directive:

 

[Alec_t]

What LED spec did you use to simulate getting 0.6V?

NSCW100 (one of the LEDs in the default LTS installation).

 

[john2k]

Thank you. It seems that if I try and use a 1.7V@20mA LED then the high end of the voltage is just over 0.7V but if i use a higher forward voltage LED then it drops the voltage. Also, is it correct that if I change the 1M ohm resistor to a higher value then the switching time will increase and if I decrease it then it will decrease? So right now with the 1M ohm resistor its about 3 seconds, if i increased to 2M ohm then this time will extend to possibly double and if I decreased it by half then it will half?

And the 10K ohm resistor just before the output, that seems to effect the voltage output. So whatever LED I choose, once I have the LED on there and if I wanted a certain voltage output then I could adjust that 10K ohm resistor right?

 

[narkeleptk]

I was thinking of using this same schematic for some o2s simulation but never get around to testing it out. If you do try the real thing, let me know how it works out for you.

 

[Alec_t]

the LED's suggested for this is 1.7V@20mA

Also, is it correct that if I change the 1M ohm resistor to a higher value then the switching time will increase and if I decrease it then it will decrease?

Yes.

if I wanted a certain voltage output then I could adjust that 10K ohm resistor right?

The 10k affects the output voltage, but I don't know what you mean by 'a certain voltage'.

 

[john2k]

The 10k affects the output voltage, but I don't know what you mean by 'a certain voltage'.

For example in your graph with a NSCW100 LED you were getting the high peak voltage of just above 0.6V and low of 0.0V. If I wanted the high peak to be 0.7V and the LED i used doesnt give me that, then technically swapping that 10K resistor should allow me to make slight adjustments right?

 

[Ylli]

Tweaking either the 10K or the 100K on pin 3 will change the output voltage. If you want to increase the output voltage, increasing the 10K or reducing the 100K would do that. Personally, I'd reduce the 100K and leave the 10K alone.