Does anyone know how to use the digital potentiometer DS1882 - diyAudio
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Old 16th May 2015, 04:49 AM   #1
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Default Does anyone know how to use the digital potentiometer DS1882

I'm planning to use this digital potentiometer in my portable amp but i'm unsure how to implement it. According to the datasheet, i need to write the configuration for the potentiometer to the EEPROM so i just need to write it only one time? And searching for DS1882 show some implements with micro controller like these:
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Click the image to open in full size.
What does these micro controller do? Thanks!
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Old 16th May 2015, 05:16 AM   #2
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Location: Los Angeles
Quote:
Originally Posted by proid View Post
What does these micro controller do? Thanks!
Any time you want to change the volume new control codes have to loaded to the volume control. The chip remembers the last setting in its internal EEPROM The microcontroller sends new codes to the volume controller. The micro also needs to interface to the buttons and will need to debounce the contacts in software. An easy way to do this is to look for changes and only take action after the switch 'settles' into the new state. I use 3 consecutive identical scans as 'good'.

PICs are good processors. I've used Freescale 6805s and 6808s and Intel MCS-51 family chips. If you haven't written code for micros there is a bit of a learning curve but most folks can manage pretty well and there is lots of example code available. Personally I like assembly code which is as close to machine language as you can get. Recommended technique is to write debug routines FIRST to let you KNOW you can read / debounce the switches and write to displays / indicators and such. The 'debug' routines can be used in the final product usually with minor to no alterations then add the 'main line'. Don't be afraid of 'interrupts'. Many starters think 'polling' is a good way to do things and for some tasks that's true but for others polling almost assures failure. What you see in simulators is not at all what happens in the real world. Data arrives when it arrives and is best dealt with with interrupts to just stop a current task and deal with the new higher priority.

Don't be afraid of it. It can be fun.
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Old 22nd December 2015, 01:58 AM   #3
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I am planning to build a preamp with volume control using DS1882. From the datasheets DS1882 can be supplied up to +/-7V of supply. But most of the preamp circuits I have seen and thinking to build are using at least +/-9 to +/-15v of power supply.
So do we need to have separate power supply for DS1882 and preamp following it or can we use the same power supply for both?
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Old 22nd December 2015, 04:45 AM   #4
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Quote:
Originally Posted by sarathssca View Post
I am planning to build a preamp with volume control using DS1882. From the datasheets DS1882 can be supplied up to +/-7V of supply. But most of the preamp circuits I have seen and thinking to build are using at least +/-9 to +/-15v of power supply.
So do we need to have separate power supply for DS1882 and preamp following it or can we use the same power supply for both?
You can use the same but it has to be +/- 7 Volts. Running multiple supplies is not difficult at all. If I were doing it I'd probably opt for split 15s and use local regulators for the DS1882.

Since the data sheet specifies VCC before VDD, the local regulators would turn on slower which is what you want. LM317/337 with a capacitor to ground as recommended will do nicely.

G

Last edited by stratus46; 22nd December 2015 at 04:58 AM.
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Old 22nd December 2015, 06:16 AM   #5
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Quote:
Originally Posted by stratus46 View Post
You can use the same but it has to be +/- 7 Volts. Running multiple supplies is not difficult at all. If I were doing it I'd probably opt for split 15s and use local regulators for the DS1882.

Since the data sheet specifies VCC before VDD, the local regulators would turn on slower which is what you want. LM317/337 with a capacitor to ground as recommended will do nicely.

G
could you please clarify "opt for split 15s and use local regulators for the DS1882" ..

Also would it be better to run
- the preamp at higher voltages and DS1882 at lower at +/-7v
(here power supply would be complex but we will be free to use any preamp)
- or use a opamp as preamp and run both opamp and DS1882 at +/-7v
(here power supply would be simple but we may have to restrict preamp being used)
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Old 22nd December 2015, 08:57 AM   #6
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Quote:
Originally Posted by sarathssca View Post
could you please clarify "opt for split 15s and use local regulators for the DS1882" ..

Also would it be better to run
- the preamp at higher voltages and DS1882 at lower at +/-7v
(here power supply would be complex but we will be free to use any preamp)
- or use a opamp as preamp and run both opamp and DS1882 at +/-7v
(here power supply would be simple but we may have to restrict preamp being used)
Personally I would choose +15 and -15 Volt supplies for all of the preamp except for the DS1882 which requires + 7 and -7 Volts. For that I would use an LM317 for the positive 7 and an LM337 for the negative 7 Volts. IIRC the resistors would be 121 ohms and 549 ohms. This will be slightly lower than 7 Volts (6.92).

I disagree on being 'complex'. The 2 regulators, resistors and capacitors will add maybe 30 holes on the board which I consider trivial.

G
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Old 22nd December 2015, 11:54 AM   #7
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Quote:
Originally Posted by stratus46 View Post
Personally I would choose +15 and -15 Volt supplies for all of the preamp except for the DS1882 which requires + 7 and -7 Volts. For that I would use an LM317 for the positive 7 and an LM337 for the negative 7 Volts. IIRC the resistors would be 121 ohms and 549 ohms. This will be slightly lower than 7 Volts (6.92).

I disagree on being 'complex'. The 2 regulators, resistors and capacitors will add maybe 30 holes on the board which I consider trivial.

G
Hi G2,

Thanks for the inputs..
regarding the power supply i mentioned as getting complex as was thinking of couple of other things also like
- i need to get another +5v for microcontroller , source select relays and the remote control receiver
- also thinking may be sometime later after initial build is working (may be with batteries or linear power supply) to get the power from power supply of the main amp (powered by 19v laptop brick power supply) by using a dc-dc converter to get +/-9 or 15v for preamp.
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