I am currently building a Power Supply with a current limiter. The first version I built used to have two potensiometers (one for voltage and one for current regulation)... trivial stuff! Now, I am running an Arduino project in which I would like to take one step further and add some digital control by using, well... two digital potensiometers!
The thing is that I want to keep both analog and digital functionality so I have to switch between the two ways of control.
Each potensiometer has 3 pins and I have 4 potensiometers in total (1 analog for volts, 1 analog for amps, 1 digital for volts and 1 analog for amps).
The PCB has 3 pins for each potensiometer (6 pins in total). So, I have to switch the 6 connections of the PCB so that they connect either with the 6 pins of the two analog potensiometers or with the 6 pins of the two digital potensiometers. *
Please tell me if you happen to know any IC, or if you have any idea (other than using 12 transistors plus the extra resistors!) so I can do this in an easy way ? I guess that I need something like a digital Relay (Solid State Relay) but I am asking for a cheap and easy solution...
This is also shown in the following two conditions as a sketch :
condition 1 : Power Supply controlled by the DIGITAL potensiometers. The PCB pins are connected to the digital POT pins.
[ DIGITAL POT 1 Pin 1 ] <----- [ PCB Pin 1 for POT 1 ] [ ANALOG POT 1 Pin 1 ]
[ DIGITAL POT 1 Pin 2 ] <----- [ PCB Pin 2 for POT 1 ] [ ANALOG POT 1 Pin 2 ]
[ DIGITAL POT 1 Pin 3 ] <----- [ PCB Pin 3 for POT 1 ] [ ANALOG POT 1 Pin 3 ]
[ DIGITAL POT 2 Pin 1 ] <----- [ PCB Pin 1 for POT 2 ] [ ANALOG POT 2 Pin 1 ]
[ DIGITAL POT 2 Pin 2 ] <----- [ PCB Pin 2 for POT 2 ] [ ANALOG POT 2 Pin 2 ]
[ DIGITAL POT 2 Pin 3 ] <----- [ PCB Pin 3 for POT 2 ] [ ANALOG POT 2 Pin 3 ]
condition 2 : Power Supply controlled by the ANALOG potensiometers. The PCB pins are connected to the analog POT pins.
[ DIGITAL POT 1 Pin 1 ] [ PCB Pin 1 for POT 1 ] -----> [ ANALOG POT 1 Pin 1 ]
[ DIGITAL POT 1 Pin 2 ] [ PCB Pin 2 for POT 1 ] -----> [ ANALOG POT 1 Pin 2 ]
[ DIGITAL POT 1 Pin 3 ] [ PCB Pin 3 for POT 1 ] -----> [ ANALOG POT 1 Pin 3 ]
[ DIGITAL POT 2 Pin 1 ] [ PCB Pin 1 for POT 2 ] -----> [ ANALOG POT 2 Pin 1 ]
[ DIGITAL POT 2 Pin 2 ] [ PCB Pin 2 for POT 2 ] -----> [ ANALOG POT 2 Pin 2 ]
[ DIGITAL POT 2 Pin 3 ] [ PCB Pin 3 for POT 2 ] -----> [ ANALOG POT 2 Pin 3 ]
@ bilbo : Thank you very much for your quick reply and your help! You suggested exactly what I was looking for!
@ KE7GKP : Thank you very much for your concern, and your help. I will try to answer all of your questions (although the answers don't really matter...).
First of all please take a look at the URL below. You will see what is the IC addressed as a 'Digital Potensiometer'.
Digital Potensiometers (Nonvolatile Memory) >>> http://www.analog.com/static/imported-files/data_sheets/AD5233.pdf
The digital potensiometers can change their values in 'steps' (as you would expect) and can be controlled by the Arduino and some logic (by using Up and Down buttons for example). The analog potensiometers as you already know can take infinite values of resistance between two limits.
Both potensiometers (or POTs as an abbreviation) are connected in the main (and only) board of the Power Supply (which I call just a PCB = printed circuit board) in a fashion such as they act as a voltage divider which controls an OpAmp (operational amplifier). This holds for each one of them. Each OpAmp is a 741 to be more precise.
I will NOT combine the analog and digital POTs into two 'Rotary Encoders' using Arduino. I will only switch between the two approaches. The analog POTs will change the values (of Volts and / or Amps) by rotation of the hand (classic method we are all used to) and the digital POTs will change the values (of Volts and / or Amps) by pressing buttons!
The Arduino that I am using is a Duemilanove.
Thank you again for your concern and your help! I hope that everything is clear now!
P.S. : If you have any more questions, please ask! And if anyone comes up with any more ideas about the problem, please share!!!
Thank you very much! You were all very helpful and inspiring! XD
Now, after some research, I am thinking of using 3 items of the DG211 ICs which seem to be quite cheap. Each IC is consisted of a "4-channel SPST switches".
But before that, I still have one question >>> What is the use of the (-V) and (+V or substrate) pins ?!.
Would someone be kind enough to take a quick look at the pinout of the first page of this PDF? >>> http://www.intersil.com/data/fn/fn3118.pdf ?
I think that GND and VL(+5V) are for the TTL compatibility, so I guess I should power that from the same source like the Arduino. But are the other two pins necessary or should I leave them N/C (not connected).
You need the other pins connected. For your case, connect V- to GND and V+ to +5V. It looks like the switching part of the IC is driven by some amplifiers that are powered by the V- and V+ pin.
@ Ilektron : Thank you very much! That's exactly what I will do!
@ bilbo :
The main reason I went with SPST was that I couldn't find SPDT chips that would be equally cheap and with all the pins the same (the ones I found had some inputs inverted, so this required extra work and logic design from my part)... But the main thing was the price! One more thing was the fact that this specific ones I chose seem to have great response on a wide range of voltages).
I have ordered samples before (from NI) and the company replied and shipped them very quickly! The samples were also of excellent quality and they still serve well! So I guess I'll try what you suggested!
