---- START NEW MESSAGE --- Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-8.05) id A6C8448023E; Thu, 29 Jan 2004 13:10:32 -0800 Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <15.00CC32DC@cherry.ease.lsoft.com>; Thu, 29 Jan 2004 15:18:59 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8e) with spool id 0747 for PICLIST@MITVMA.MIT.EDU; Thu, 29 Jan 2004 15:18:51 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 1543; Thu, 29 Jan 2004 15:18:12 -0500 Received: from bandit.rpmservers.com [207.44.248.37] by mitvma.mit.edu (IBM VM SMTP Level 430) via TCP with ESMTP ; Thu, 29 Jan 2004 15:18:12 EST X-Comment: mitvma.mit.edu: Mail was sent by bandit.rpmservers.com Received: from udhcp-wlan1005.public.engin.umich.edu ([141.213.121.0] helo=ubasics.com) by bandit.rpmservers.com with asmtp (TLSv1:RC4-MD5:128) (Exim 4.24) id 1AmIc5-0004lo-OV for PICLIST@MITVMA.MIT.EDU; Thu, 29 Jan 2004 14:18:09 -0600 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6) Gecko/20040113 X-Accept-Language: en-us, en, zh, zh-cn, zh-hk, zh-sg, zh-tw, ja, ko, ko-kp, ko-kr MIME-Version: 1.0 References: <20040129190421.GA7467@flarenet.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bandit.rpmservers.com X-AntiAbuse: Original Domain - mitvma.mit.edu X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - ubasics.com Message-ID: <40196A81.3060105@ubasics.com> Date: Thu, 29 Jan 2004 15:18:09 -0500 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: "M. Adam Davis" Subject: Re: [EE] Generating a Positive Voltage from Negative To: PICLIST@MITVMA.MIT.EDU In-Reply-To: <20040129190421.GA7467@flarenet.com> Precedence: list X-RCPT-TO: Status: U X-UIDL: 371856327 Actually most of these devices simply rely on the computer driver driving two of these signals high to give positive 9-12v. However, the simple answer to your specific question is that for low currents (which is all you can reliably pull from a serial port) you generally use a capacitor charge pump to invert the voltage. There are chips 'out there' which do it for you, but they are not common. Study how this circuit operates: http://www.piclist.com/techref/microchip/pwmvee.htm It converts a positive voltage into negative with only a square wave, two caps, two diodes, and a resistor. The premise is the same for your need. There are other similar circuits with operating descriptions, and this has been discussed in the piclist in the past. Good luck! -Adam Robert James Kaes wrote: >Hi, >Does any one have a circuit for generating a positive voltage from a >negative source? I'm connecting a circuit to the serial port of a >computer where there is -10VDC, but I need a positive voltage. I've >found lots of circuits that will generate a negative voltage from a >positive, but not the other way around. > >I know a serial mouse needs to do this to operate, but I haven't been >able to find the circuitry for it. > >Thank you for any help you can provide. > -- Robert > >-- > Robert James Kaes --- Flarenet Inc. --- (519) 426-3782 > http://www.flarenet.com/consulting/ > * Putting the Service Back in Internet Service Provider * > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. > > > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. .