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change resistor value/range

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I have no option but to use a 100k potentiometer, the adjustable range only needs to be 100k say from 400k- 500k is there any way to do this with resistors, please explain..... thankyou in advance........ Steve
 
hi.
Connect a 390K resistor in series with the 100K pot

E
 
I think this what you want...

The voltages at node A, B, and Tap are plotted vs pot position (%)
 

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The reason I require a 100k potentiometer is because that is the highest value I can find in a digital pot..... the rated tolerance is 20 percent. ..... any idea how far off at any given moment the value will change.......? I live in minnesota, it can be -20 or 90?... will adding a resistor to the 100k pot give me a different tolerance? or no difference, or worse? {/=\ I+I \=/ I-I } = ? what would the graph look like in the 400k-500k range with a 20 percent pot and a 1percent 392k resistor?
 
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Will a digital pot allow you to have other than 0V on the lower terminal (node B in my diagram)?
 
The resistance is for charge/dischare of capacitor. for a delay........ cmos circuit.....so the potentiometer charges the capacitor under the threshold. resistor charge capacitor.....(-) resistor idischarge capacitor (+) delay....... the voltage is 5v, but the resistance is key...for delay.......everyone says ne555, but the resistors and capacitors are doing the timing, the ne555 makes a digital signal.... ?
 
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0v

Will a digital pot allow you to have other than 0V on the lower terminal (node B in my diagram)?

please explain what you mean? :confused: I understand the chart related to voltage, but not sure of question? I don't have the schematic...... so cannot post it.. the pot is a Maxim DS 1809-100 up/down non-vol. I am using in a simple 1-4 second delay timing circ. in the end ... will probly just change the cap and resistor values........ but...... if you want to post the correct values .....and schematic.......for 100k pot. The circiut is .........0v...... apply 5v (adjustble 1-5 second delay) then 5v out [logic/cmos] you can only use 3 resistors and a cap. no IC or crystal
 
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hi,
This clip is from a Maxim d/s.

E.
 

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