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04-15-2008

The experimenter's pot - Digital Potentiometer

Joseph Yumul

The experimenter's pot is a solid state potentiometer using Dallas semiconductor's DS1869 and National's LM78L05 two electrolytic capacitor two small push button switch and two optional Molex connector. This project is very useful especially in finding the right value of resistor in your experiments, you can attach this circuit to your next project that uses a pot or trimmer cause there are three types of DS1869 these are:

  • DS1869-10 which is 10K
  • DS1869-50 a 50K version
  • DS1869-100 the 100K version


Schematic

As you can see, the circuit is powered from a 9V power supply (actually any 9 V power source will work, as long as the current rating is not less than 25 mA) stepped down to 5 V by the LM78L05 IC and two filter capacitor one for the input and one for the output, the wiper arm's position is stepped by pressing SW2 for adding the resistance of wiper arm to high terminal and SW1 for decreasing just like an ordinary mechanical potentiometer adding the resistance to high terminal decreases the resistance to low terminal.

Parts List:

  • C1 10 uF / 16 V Electrolytic capacitor
  • C2 0.01 uF / 50 V Ceramic capacitor
  • U1 LM78L05
  • U2 DS1869 (see notes)
  • SW1, SW2 Small push button switch

Notes:

The maximum wiper current allowed through the DS1869 is only 1 milliamps. There are three types of DS1869

  1. DS1869-10 use this chip if you want to make a 10K version
  2. DS1869-50 for a 50K version pot.
  3. DS1869-100 for the 100K version

The experimenter pot - Digital Potentiometer
PCB

The schematic and the board is drawn using expresspcb, it is available for download you can etch your own PCB using TTM (Toner Transfer Method).

Download this circuit in ZIP

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