--- peng3002 <peng3002@...> wrote:
use any size pot and resistors that you want (as long as they are not
too small). Once you pick your pot, you will find that you use the
resistors on each end to set the overall range of the offset pot.
Look at the string from +15 to -15 and realize this is a simple
voltage divider. If each element is the same size, you will get
equal voltage drop across each. So, the range of the pot will be 10
volts (+/-5). If you want the offset range bigger, reduce the size
of the resistors compared to the pot and vice versa. So, if you
change to a 50K pot and like the 10 volt offset range, change to 47 K
resistors.
Or, you can just leave the end resistors out, and increase the size
of the 47K resistor that connects the pot wiper it to the op amp to
150K.
BTW, all this assumes you have the range trimmer turned to full 47K.
The more you reduce the size of the trimmer, the smaller your actual
output range will be.
Larry H
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> I am building a joystick controller based on the schematic at CGSYou do not have to change the resistors, but you may want to. You can
> site. The offset pot is specified as 25K but I would like to use
> 50K because that's all I have onhand. Will this work, would I need
> to change the 22K resistors coming from the +/- supplies to
> different values ?
use any size pot and resistors that you want (as long as they are not
too small). Once you pick your pot, you will find that you use the
resistors on each end to set the overall range of the offset pot.
Look at the string from +15 to -15 and realize this is a simple
voltage divider. If each element is the same size, you will get
equal voltage drop across each. So, the range of the pot will be 10
volts (+/-5). If you want the offset range bigger, reduce the size
of the resistors compared to the pot and vice versa. So, if you
change to a 50K pot and like the 10 volt offset range, change to 47 K
resistors.
Or, you can just leave the end resistors out, and increase the size
of the 47K resistor that connects the pot wiper it to the op amp to
150K.
BTW, all this assumes you have the range trimmer turned to full 47K.
The more you reduce the size of the trimmer, the smaller your actual
output range will be.
> Also, I have spring centered joysticks and would like to getYes. That will also give your joystick a 10 volt range (+/-5)
> negative voltages when I pull down and positive going up. Can I
> just attach the pot end that goes to ground to the negative
> supply ? If so will I need a resistor matched to my joystick in
> series.
Larry H
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