Hi Bernard,

I understood what you were saying, but what I was trying to say is that while the circuit is sectioned up for testing and for me to learn, the 1.9v will come from the sensor (voltage source) and go to the measuring device (voltage reader). So I have to tap into this 1.9v voltage coming from the sensor and oscillate it to keep the measuring device happy. That's why I drew it the way that I did.

Sorry I didn't explain this in a better way, maybe I'm still just not getting it? Or am I on the right track now that I've tried to explain it better?

 

You could use a V divider from 5 V supply. 1.6k to +5V, 1k to gnd., 1,9V at junction. That is some sensor, do you have any info on it?

 

Unfortunately, the only data I have on it is how it is supposed to output, no other data besides that. I did plan on using a voltage divider on the bench before testing it on the sensor.

 

Unfortunately, the only data I have on it is how it is supposed to output, no other data besides that. I did plan on using a voltage divider on the bench before testing it on the sensor.

You have no part number for it? You won't share the data you have? How can a circuit be designed for an unknown?

 

I will look for a part number, maybe there is one hidden on it.

I can share any data I have if you would like. It is a 0 to 5v pressure sensor with 0v meaning it is damaged, so the scale is probably ~.5v and up.

I'm designing based on observed scenarios with my DMM and Oscope.

 

Finally you tell us that the Sensor is an output device, 0-5V, so in origional drawing outputs were feeding outputs, no wonder we were confused-or still are. Post # 17, or better #19 will do what you want. The input to the 10% oscillator is Sensor-1.9V, not C. Connect meter across 100k load.
So the origional purpose was to develope a simulation of the Sensor V output??
Without SW-2 , 100k not needed-yet.

 

I'm sorry for the confusion.

I built the circuit tonight and it did not work properly. I went over it a few times, so I believe it is built correctly.

I did have to make a few assumptions. I did not have a 910k resistor, so I used 2 resistors to created 950k of resistance. I also did not have a non polarized capacitor, so I used a polarized 1uF capacitor.

The voltage at the collector stays pretty solid at ~1.9v until I ground the 555 timer reset pin and then it stays pretty solid at ~1.65v

Here was the output of the 555 IC pin 3, on the oscilloscope.

 

Looks good, except the diode is backwards allowing pin 7 to discharge cap quickly. I just hooked up a C555, 330k & 1 meg, also did not have 910k, 1 μF. Pin 3 high .3 s, low .9 s.

 

I will swap that tonight and report back, ugh ... thank you

 

Hi Bernard,

I swapped the diode around and it still didn't oscillate, but I noticed that when I took it out completely, it oscillated quite nicely. The diode may have been cooked and I just didn't know it, but I'm going to try it without the diode, since I saw it oscillate nicely that way on the bench.

I'll probably install it at the end of the week and see how it does outside of the bench world and if all goes well, move it from a breadboard to a PCB.

I'll report back after some real world testing.

Thanks for all of your help, I could not have done this without your help.

 

It works great, thanks Bernard!