500k pot

Thread Starter

ale2121

Joined Mar 20, 2009
71
hi, i have a bunch of potentiometers, but not the values I need. can i add regular resistors in line with a 100k pot to get close? or, should i just use a pot that's way bigger, like a 1meg pot?
 

bertus

Joined Apr 5, 2008
19,939
Hello,

That depends on he application.
Can you post a circuit?
What is the use of the pot at this circuit?

Greetings,
Bertus
 

Thread Starter

ale2121

Joined Mar 20, 2009
71
i can't find it online. it's the stepped tone generator from the forest mims 555 book. i believe these two 500k pots control the frequency of each of the 555s in the 556.
 

bertus

Joined Apr 5, 2008
19,939
Hello,

You may use the 1M pot, the range will be twice as large.
For the 555 is this no problem.

Greetings,
Bertus
 

-SK-

Joined Apr 14, 2009
25
If you add other resistors, such as 400k in series with the 100k pot, you would only get a 5th of the range (400k-500k). Check the book to see if it gives more info on the range you need. If the range only needs to be a portion of that 500k, you could get away with a 100k and other resistors, you might lose some functionality of the circuit.
 

Wendy

Joined Mar 24, 2008
21,840
You can do what you're suggesting, but the linearity will suffer greatly. Overall, I would say it is not a problem.
 

SgtWookie

Joined Jul 17, 2007
22,201
If you need to decrease R1 from 500k to 100k, you can compensate by increasing C1 from 0.01uF to 0.047uF.

If you need to decrease R2 from 500k to 100k, you can compensate by increasing C2 from 0.1uF to 0.47uF.

Forrest M. Mims III's circuits are copyrighted material, and as such cannot be posted here without his written permission.
 
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