Nuts and Volts - April 2014

Put all switches in the “in” position. This will place all of the potentiometers in the circuit. Now, adjust the leftmost (one meg) pot until you get the desired result. If your circuit needs less resistance, put the one meg switch in the “out” position (eliminating the one meg pot). Now, adjust the 100K pot until the desired result is achieved. Again, if the resistance is still too much, put the next (10K pot) switch in the out position.

Keep repeating this procedure until you get the desired result. Once this is achieved, disconnect the clip leads from your project and place them across a digital meter (set to read resistance). Read the value, then look up that value in a chart of standard resistor values. Table 1 shows an example chart.

Get the closest standard EIA (Electronic Industries Association) value and put this in your circuit. If a standard value isn’t close enough, use combinations of series or parallel resistors to get there. In some cases, a potentiometer can be substituted for the value and adjusted to get the exact match.