Return-Path: Received: (qmail 82816 invoked from network); 12 May 2004 16:58:48 -0000 Received: from unknown (HELO ptb-mxscan01.plus.net) (212.159.14.235) by ptb-mailstore01.plus.net with SMTP; 12 May 2004 16:58:48 -0000 Received: (qmail 78226 invoked from network); 12 May 2004 16:58:47 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 Received: from ptb-mxcore01.plus.net (212.159.14.215) by ptb-mxscan01.plus.net with SMTP; 12 May 2004 16:58:46 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1BNx4A-000K7x-Dg for dave@picks.force9.co.uk; Wed, 12 May 2004 16:58:46 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1BNx3Y-0001Z6-1Y for rs_out_1@blacksheep.org; Wed, 12 May 2004 17:58:08 +0100 Received: from [213.232.95.59] (helo=relay.salmark.net) by post.thorcom.com with esmtp (Exim 4.14) id 1BNx3X-0001Yx-9b for rsgb_lf_group@blacksheep.org; Wed, 12 May 2004 17:58:07 +0100 Received: from cmsrelay01.mx.net ([165.212.11.110]) by relay.salmark.net with smtp (Exim 4.24) id 1BO3bt-0004bQ-Pk for rsgb_lf_group@blacksheep.org; Thu, 13 May 2004 00:58:01 +0100 Received: from cmsapps02.cms.usa.net (165.212.11.138) by cmsoutbound.mx.net with SMTP; 12 May 2004 16:57:49 -0000 Received: from usa.net [151.41.154.97] by cmsapps02.cms.usa.net (ASMTP/dibene@usa.net) via mtad (C8.MAIN.3.13N) with ESMTP id 338ieLq6U0298M38; Wed, 12 May 2004 16:57:46 GMT X-USANET-Auth: 151.41.154.97 AUTH dibene@usa.net usa.net Message-ID: <40A2578C.2080600@usa.net> Date: Wed, 12 May 2004 18:57:48 +0200 From: Alberto di Bene User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: LF Mailing List X-Spam-Score: 2.8 (++) X-Spam-Report: autolearn=no,FAKE_HELO_USA_NET=2.8 Subject: LF: VDC source with microvolt resolution Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.8 required=5.0 tests=FAKE_HELO_USA_NET autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 1 I wonder if someone on this list has already had a problem similar to this, and has found a simple solution. Problem: I have a super-filtered and stable DC voltage of about 8V. I need to make it variable (with negligible current requirements) from abt 0 to abt 8V, with a minimum step size of abt 10 uV. I can use part of the processing power of an AVR microcontroller for this task. One solution that comes immediately to the mind is to use a 20-bit DAC, fed somehow with that stable voltage, but I am in search of something that doesn't need hard-to-find components. I played with the idea of a charge pump, where you control with a couple of output bits of a port of the micro the charge and discharge of a capacitor for variable lenghts of time, so to achieve the wanted result, but I am unsure of the implementation details. The response time requirements are very relaxed, there will be an adjustment of that voltage let's say once every two minutes or more. Has anybody suggestions or links ? Many thanks 73 Alberto I2PHD