I am a new user as I hope the community may be able to assist me. I have been looking for options of a DIP-8 Digital Potentiometer for a school electronics experiment, but the selection available seems very limited. The main requirements is that it would be dip to be hand soldered by the students and also be able to be controlled without a microcontroller. So far in all of my searches I have found the Maxim DS1804/DS1809, and the AD5220, and honestly I was looking for a lower cost solution that our school could buy a few hundred of for experiments (low budget).
Does anyone else know of any other models that may work for me?
Also I was seeing some that list as 3-wire Serial such as the Intersil X9318 which datasheet shows "The
position of the wiper element is controlled by the CS, U/D, and INC inputs. " and being new with these it seemed like this style could be controlled manually without a microcontroller, but I did not see any example schematics or circuits of this so I wanted to ask you all if that was possible.
Thanks in advance as any suggestions or comments are appreciated.
Any DAC (digital to analog converter) can be used as a potentiometer. The problem with the DIP-8 versions is that they are serial controlled and that will be difficult to do by hand. Possible, but difficult and error prone since humans aren’t very good at long sequences. However, it’s easy to control an 8-bit parallel input DAC with a bunch of DIP switches.
For unipolar (0-5V) operation, the configuration is simple. However, if you need to handle bipolar signals, then it becomes a bit more complex, since they will probably require external op amps.
Take a look at the MX7533, I think it’ll do what you need.
Those digital pots can be used ‘manually’. All it takes is a few switches (with proper switch-debounce filtering and pull up resistors). There is no limit on how long you can hold the pulses. Only the pulse edges need to be of a certain steepness. But it will take quite a bunch of keypresses to scan the desired resistance level.
Take a look at the AD5220 data sheet. Figure 1 is a “Typical Push-Button Control Application”.
If you want at least 100, you can buy them directly from AD for $1.54, which is significantly less than DigiKey et. al. Don’t know if they would sell smaller quantities, but they might, especially for an educator.