diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Analog Line Level (http://www.diyaudio.com/forums/analog-line-level/)
-   -   Using a Precision Current Source to drive an LDR attenuator (http://www.diyaudio.com/forums/analog-line-level/178133-using-precision-current-source-drive-ldr-attenuator.html)

maxw 29th November 2010 03:18 PM

Using a Precision Current Source to drive an LDR attenuator
 
Has anyone actually tried using a current source based on digital potentiometer to drive a LDR attenuator? I've seen it mentioned in the massive Lightspeed thread but has anyone actually tried it?
It would be good for folks who want an LDR based attenuator with digital control (for remote control, displays, integration etc).
Is this how the DIY Paradise Eva works?

Anyway, I was looking at this app note from Maxim which shows pretty much the generic current source based on a digital potentiometer and a shunt:
Precision Current Source is Software-Programmable - Maxim

http://www.maxim-ic.com/images/appno.../3464Fig01.gif

I want to try it but use a regulated PSU instead of the shunt IC. By using their forumula Rsense should be 200R when using a 5V supply, but I'm not sure what to use for Rs? Can anyone explain what this resistor is for? I'm thinking its to limit the amount of current going through the digital potentiometer wiper as they can generally only handle 1mA...

maxw 29th November 2010 03:27 PM

1 Attachment(s)
I'm thinking something like this. Any pointers?

vt4c 5th December 2010 07:20 AM

Almost the same concept but less complicate and does not use as many i.c.s. :)


Quote:

Originally Posted by maxw (Post 2380994)
Has anyone actually tried using a current source based on digital potentiometer to drive a LDR attenuator? I've seen it mentioned in the massive Lightspeed thread but has anyone actually tried it?
It would be good for folks who want an LDR based attenuator with digital control (for remote control, displays, integration etc).
Is this how the DIY Paradise Eva works?

Anyway, I was looking at this app note from Maxim which shows pretty much the generic current source based on a digital potentiometer and a shunt:
Precision Current Source is Software-Programmable - Maxim

http://www.maxim-ic.com/images/appno.../3464Fig01.gif

I want to try it but use a regulated PSU instead of the shunt IC. By using their forumula Rsense should be 200R when using a 5V supply, but I'm not sure what to use for Rs? Can anyone explain what this resistor is for? I'm thinking its to limit the amount of current going through the digital potentiometer wiper as they can generally only handle 1mA...



All times are GMT. The time now is 11:26 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2