Arachnid part sub question

[swelchy]

Would it be fine if I subbed C7 15P for a or 30P? Tried measuring my 30p's and the lowest I found in the stash were 28P... Or should I go ahead and order the spec'd cap?

 

[Mcknib]

The FV1 datasheet says that capacitor can range from 15 to 27pf depending on the crystal manufacturer

 

[carlinb17]

You could also put two 30pfs in series to create your 15pf

Conversion Calculator Series and Parallel Capacitor | DigiKey

Calculate the total series and parallel capacitance of a circuit using DigiKey's Series and Parallel Capacitor calculator.

www.digikey.com

 

[swelchy]

You could also put two 30pfs in series to create your 15pf

Conversion Calculator Series and Parallel Capacitor | DigiKey

Calculate the total series and parallel capacitance of a circuit using DigiKey's Series and Parallel Capacitor calculator.

www.digikey.com

HMM. I have never done that... going to look that up and see what it looks like!

 

[swelchy]

OK.. So what am I doing wrong? I've tried soldering the legs of two ceramic capacitors at 30p together and test them on my tester an I get no reading... tried with ceramic and the monolithic ones too.... tried several... and tested each one before soldering for value.. solder them and then it reads error...

 

[Robert]

Very few DMMs can measure capacitance accurately below 1nF.

I use a little cheap $40 Amazon capacitance meter for low-value caps. Everyone likes to make fun of me about it.

(Just wait, the pic will show up shortly, I guarantee)

 

[carlinb17]

Here is my cheapo one works great or so I think

 

[swelchy]

I'm using a cheapo meter as well.. it will show the 30p and if I put two caps in there parallel they will double the value.... but when I put them in series it shows an error or no reading.....

 

[swelchy]

 

[fig]

Very few DMMs can measure capacitance accurately below 1nF.

I use a little cheap $40 Amazon capacitance meter for low-value caps. Everyone likes to make fun of me about it.

(Just wait, the pic will show up shortly, I guarantee)

This li’l guy?

 

[fig]

I'm using a cheapo meter as well.. it will show the 30p and if I put two caps in there parallel they will double the value.... but when I put them in series it shows an error or no reading.....

Perhaps 30p is the bottom range

 

[Robert]

If you're measuring ~30pF from each one individually and ~60pF when they're in parallel you can feel fairly good about the value when they're connected in series.

 

[Jeff M.]

Another way to confirm it is to measure a 100pF cap (to see how far off 100 it is) and measure that in parallel with the “two 30pF series contraption from post #5” …much like you did with the two 30’s to get 60pF.

Then just subtract 100 (or whatever the 100pF cap measured).

I use that dual-cap method when measuring low-value caps.

 

[swelchy]

Another way to confirm it is to measure a 100pF cap (to see how far off 100 it is) and measure that in parallel with the “two 30pF series contraption from post #5” …much like you did with the two 30’s to get 60pF.

Then just subtract 100 (or whatever the 100pF cap measured).

I use that dual-cap method when measuring low-value caps.

great advice! thanks

 

[Chuck D. Bones]

Next time just use the right capacitor. XTAL oscillators are finicky and kludging them is a bad idea. Disk ceramic caps are unreliable and I avoid them like the plague (whichever plague is going around these days).

 

[swelchy]

Next time just use the right capacitor. XTAL oscillators are finicky and kludging them is a bad idea. Disk ceramic caps are unreliable and I avoid them like the plague (whichever plague is going around these days).

Noted…. I went ahead and used them in series and it worked out great… Going to order some better caps and a better range of values on my next stock up..

 

[Chuck D. Bones]

Silver mica is recommended. You can find 'em on eBay. Best bet is to buy a selection.