good to hear. by adjusting the pots what should be taking place? what should I be looking for?

 

good to hear. by adjusting the pots what should be taking place? what should I be looking for?

The one for the slow schmitt trigger oscillator changes the time the motor will run at a certain speed, i.e. the output of the LM258 should be constant.
You can check if the potentiometer works as intended. Unless you have a resistor in series with the pot don't adjust it towards 0Ohm!

The other potentiometer in the random part... where was it again?

 

there's a total of 3. the first I in 500k that sits in between pin 1 and 2 of the 40106 (replaces to 220k in the top left of the schematic)

the second is a 100k (replaces 100k) that sits between the positive input of the op amp and ground.

the third is a 20k (replaces 15k) that sits between the negative and the output of the op amp.

 

there's a total of 3. the first I in 500k that sits in between pin 1 and 2 of the 40106 (replaces to 220k in the top left of the schematic)

the second is a 100k (replaces 100k) that sits between the positive input of the op amp and ground.

the third is a 20k (replaces 15k) that sits between the negative and the output of the op amp.

The 100k adjusts the offset of the voltage at the output, the 20k the gain ( how much it changes between steps. It makes only sense to test them when connected to the 555, then they will change its' frequency.

Verify if they change the output voltage but then adjust them to the values indicated in the schematic.

 

thanks. what does changing the offset of the voltage at the output effect? and what about the 500k pot?

I have to go get a switch and a 10 nF capacitor so that I can turn the random on and off.

 

thanks. what does changing the offset of the voltage at the output effect? and what about the 500k pot?

I have to go get a switch and a 10 nF capacitor so that I can turn the random on and off.

The offset will change the midpoint of the via pin 5 of the 555 adjustable freq range.

The 500k will determine the time interval the D-flipflops are updated. Their output states remain constant during this interval. Therefore the voltage that goes to pin 5 of the 555 also remains constant. (a few seconds for example)

 

so, I hooked the pseudo random portion up and got it hooked up to the scope. the output voltage has been jumping around from 3.11v to a max of 9.45v. the one thing that I adjusted that I would prefer to stay is the 500k pot. I have it turned all the way to max resistance because it slows down the the intervals at which each change happens. is it ok to leave it there?

I finished making the logic board it, I couldn't find a 10nF cap at radio shack, they don't carry nF only uF. as for being able to turn on and off, the random part, I have to wait. tomorrow the goal is to set everything up and test like you described earlier.

more to come.

 

so, I hooked the pseudo random portion up and got it hooked up to the scope. the output voltage has been jumping around from 3.11v to a max of 9.45v. the one thing that I adjusted that I would prefer to stay is the 500k pot. I have it turned all the way to max resistance because it slows down the the intervals at which each change happens. is it ok to leave it there?

Great.

You can either leave it adjusted to 500k or increase the capacitor at the logic gate input.

 

Here's a photo of the pseudo random portion:

The rest of the logic portion:

and a snapshot of the oscilloscope during it's random voltage output:

This is a picture of the first one I made. it's a bit crowded and there is no way to remove the voltage from the FETs without un-soldering them.

 

Nice work. I can't see anything on the scope screenshot though. It says "waiting for trigger". Is this the right one? I would be interested in seeing the waveform.

 

That was the picture, it was set on voltage, the wave that it displayed was very small. With my lack of knowledge on how to use this scope, what setting does it need to be on?

 

You can either leave it adjusted to 500k or increase the capacitor at the logic gate input.

which capacitor are you talking about?

 

That was the picture, it was set on voltage, the wave that it displayed was very small. With my lack of knowledge on how to use this scope, what setting does it need to be on?

I see, it's the timebase, it's set to 50us. Set it to a 1sec or more, the screen should then show the different levels of voltage on one screen.

which capacitor are you talking about?

10uF at the input of the 40106.

 

Nice work. I can't see anything on the scope screenshot though. It says "waiting for trigger". Is this the right one? I would be interested in seeing the waveform.

I figured it out, standby I am uploading pictures right now.

 

These are 20 second screen shots in succession:

 

That's good enough for your application I guess. It jumps up and down, more or less. Although I don't like the noisy part at lower voltages.
Maybe you can later post a picture also with the 500k pot adjusted to a lower value, so that more jumps are visible on the screen and one gets a better idea of the randomness.. (but that's not really important, it's personal interest. )

Next week I will try to find out what's the reason for the noise. You do have a bypass capacitor on the ICs power supply pins, right?

In parallel (if you have the time) you can try to catch one of these noisy parts (at about 4V or so) with a lower timebase and maybe 200mV or 500mV per division. It looks like an oscillation but it can't really be seen on these pictures.

Good work!

 

Maybe you can later post a picture also with the 500k pot adjusted to a lower value, so that more jumps are visible on the screen and one gets a better idea of the randomness.. (but that's not really important, it's personal interest. )

I can definitely do that for you.

You do have a bypass capacitor on the ICs power supply pins, right?

everything that is NOT inverted is on the logic board (except the 1Meg pot)

With the random portion on do I need to have the 1 Meg pot? what will that change when the random portion is on?

 

With bypass cap I meant the 100nF near the LM258 on the random schematic.

With the random portion on do I need to have the 1 Meg pot? what will that change when the random portion is on?

It will also affect the frequency.
For the simulation I just left it at 1M.

I see that if you wanted the random part to always act in the same way, the 1M pot value should be fixed when random is ON.

Example: You adjust random pots (gain/offset) to work the way you want, then switch to random OFF, then adjust the 1M to e.g. 750k and then switch back to random ON, it will not behave the same way.

If the 1M is the big potentiometer I've seen on the pictures, that shouldn't be a problem.

You calibrate the random part the way you need it (once) and everytime you turn random ON you adjust the pot back to 1M.

It could be done automatically but this will cost you more time (and a few more components)

 

With bypass cap I meant the 100nF near the LM258 on the random schematic.

yes there is one 100nF cap.

It will also affect the frequency.
For the simulation I just left it at 1M.

I see that if you wanted the random part to always act in the same way, the 1M pot value should be fixed when random is ON.

Example: You adjust random pots (gain/offset) to work the way you want, then switch to random OFF, then adjust the 1M to e.g. 750k and then switch back to random ON, it will not behave the same way.

If the 1M is the big potentiometer I've seen on the pictures, that shouldn't be a problem.

You calibrate the random part the way you need it (once) and everytime you turn random ON you adjust the pot back to 1M.

It could be done automatically but this will cost you more time (and a few more components)

I completely understand now.

 

Heres a snapshot of it at the lower voltage:

It jumps all around huh??

and for fear of going to 0 ohms I stopped close and here's a screen shot of the randomness: