Geotech Baracuda - How to Calculate frequency of 40106 oscillator with different C5 (6n8)

[Polymer]

I am populating the Geotech Baracuda board.

I cannot get a 6n8 capacitor where I am right now, not even from scrap box :-(

Can I use a 4.7n or 5.6n or 10n capacitor instead?

The frequency will change of course, does this effect the timings in a bad way?

I looked up freq. calculation for Schmitt trigger oscillator CMOS and found this formula:

f= 1/1.7xRC

Is this correct and which C and R values would have to be applied in the formula?
The configuration on the Geotec Baracuda with the diodes and the 40106 has me confused.

Thanks, Polymer

[Qiaozhi]

I am populating the Geotech Baracuda board.

I cannot get a 6n8 capacitor where I am right now, not even from scrap box :-(

Can I use a 4.7n or 5.6n or 10n capacitor instead?

Use a 5n6 and a 1n0 in parallel to get 6n6. That should be close enough.

[Polymer]

Use a 5n6 and a 1n0 in parallel to get 6n6. That should be close enough.

Thanks Qiaozhi.

Is the value critical though? What would it change?

I am learning about Schnitt Trigger at the moment and
it's sort of dawning on me that in the Geotech Baracuda configuration it might just be so.

I'll be receiving an oscilloscope give or take a week, so I can finally see what happens to signals when twiddling around.

[Qiaozhi]

Thanks Qiaozhi.

Is the value critical though? What would it change?

I am learning about Schnitt Trigger at the moment and
it's sort of dawning on me that in the Geotech Baracuda configuration it might just be so.

I'll be receiving an oscilloscope give or take a week, so I can finally see what happens to signals when twiddling around.

Given that a typical 6n8 (6800pF) capacitor has a tolerance of 10%, this gives a possible range in values from 6n12 to 7n48.
As you can readily see, a 5n6 in parallel with a 1n0 results in a 6n6 capacitance, which is well within the 10% tolerance range.

[homefire]

Just get close and do this. LOL

I had Issues with R7.

PPS calls for 640Hz was 757Hz.

Placed 50K Pot in line with R7 100K resister.

( Broke off Pad to R7 on one side. Wired from remaining Pad and V3 Pad. `

Now can vary PPS from 600Hz to 760Hz.

[Polymer]

Given that a typical 6n8 (6800pF) capacitor has a tolerance of 10%, this gives a possible range in values from 6n12 to 7n48.
As you can readily see, a 5n6 in parallel with a 1n0 results in a 6n6 capacitance, which is well within the 10% tolerance range.

Thanks for your patience Qiaozhi.
I managed to find one solitary 5.6n 5% on a vcr scrap board. The 1n I have.
The function of that cap still has me stumped.

I found this regarding Schmitt Trigger and that danged cap still is not explained

[Polymer]

Just get close and do this. LOL

I had Issues with R7.

PPS calls for 640Hz was 757Hz.

Placed 50K Pot in line with R7 100K resister.

( Broke off Pad to R7 on one side. Wired from remaining Pad and V3 Pad. `

Now can vary PPS from 600Hz to 760Hz.

You got me laughing Homefire - Just do it! I'm not good at following orders at best, lest I know what's up.

Yeah, I've plonked the capacitor-hybrid in the board now.

I will keep a close eye on R7 now , what was the issue?

[homefire]

R7 and your 6.8 Cap determine the timing of the oscillator. Adjusting one or the other will change the consolations. AKa your Timing pulse.