Digital Potentiometer

[breaktru]

The only match I was able to get on Farnell is 7 bit MCP4141-104E/P MICROCHIP|MCP4141-104E/P|POTENTIOMETER, DIGITAL, 100K, | Farnell Ireland
but 128 is too much to me

This D.P. requires logic control for voltage scaling and not controlled w/ a toggle switch.
Supply voltage is 2.7v to 5.5v which limits you to a single battery booster regulator.
128 steps would give you a better voltage scaling.
The 100k resistance is good for the 08100w (evercool) but not for the 04050c (booster) regulator.

 

[breaktru]

Farnell does NOT have a D.P. with a supply voltage ABOVE 2.7v-5.5v and 2.5v-6v.
Why must it be Farnell? because it has to be Ireland?

 

[mwebmaster]

Farnell does NOT have a D.P. with a supply voltage ABOVE 2.7v-5.5v and 2.5v-6v.
Why must it be Farnell? because it has to be Ireland?

basically yes because of location - as I will have to spend extra 30 bucks on delivery buying this from digikey

 

[Dalton63841]

With your digi-POT setup, with the ptn04050C, if I wanted to add a second button to separate up and down, what all would I need to do besides add a second switch on DC. I feel like DC needs to be removed from the loop in the schematic, but I want to be sure.

EDIT: nvm, I just read the datasheet. Easy peasy. I'm kind of excited to build this thing now. I'm SICK of screwing with analog POTs.

 

[breaktru]

EDIT: nvm, I just read the datasheet. Easy peasy. I'm kind of excited to build this thing now. I'm SICK of screwing with analog POTs.

Okay Dalton, sounds like you found your answer.

 

[Dalton63841]

Okay Dalton, sounds like you found your answer.

Haha yea it was like 2am and it didn't occur to me to read the datasheet until after I posted.

 

[atanlong]

I just got a few samples of the 2.7-5.0v 1kohm version of these http://www.intersil.com/products/deviceinfo.asp?pn=X9317 to test out, but they are very, very, tiny, literally about 3mmx3mm (I got the msop instead of the pdip... oops).

Havent been able to test em out yet, waiting on some caps and momentary switches. Considering how tiny they are, ill get to learn how to drag solder... yay.... lol....

Need help ..
me too, just got two samples of this X9317..
have u test em out ? how s the wiring schematic ?

 

[breaktru]

Need help ..
me too, just got two samples of this X9317..
have u test em out ? how s the wiring schematic ?

The wiper position on this chip is controlled by a 3-wire interface.. Such as a microcontroller or programmable logic device.
If you are looking to control this by using up/down switches, this is not the chip you want.

 

[atanlong]

The wiper position on this chip is controlled by a 3-wire interface.. Such as a microcontroller or programmable logic device.
If you are looking to control this by using up/down switches, this is not the chip you want.

Thank you Sir.
what type of DP from TI can i use ?

 

[CraigHB]

It's actually pretty hard to find digital pots that offer a simple up-down interface. Just about all of them are designed to be interfaced with a microcontroller using a serial data bus. The one Breaktru posted is the only one I've seen and it's not an easy part to find. Try searching the part number at FindChips.com. Mouser has them in stock, but damn, they're expensive as far as chips go.

One issue with that particular DP is that it's got an absolute maximum voltage rating of 8.0V. You'd need to incorporate a simple voltage regulator to use it with a dual cell mod since freshly charged batts in series are 8.4V. Though it's not a big deal. A simple regulator consisting of a Zener diode and resistor would probably suffice. Small linear regulators are also cheap and easy to incorporate.

I have a feeling you'd have a real hard time finding a DP with a maximum 9V operating voltage and an up-down interface. Though, I don't know for sure since I've never looked.