---------------------------------------------------------- TeamGrumman-List Digest Archive --- Total Messages Posted Sun 04/30/06: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:13 AM - Re: Handheld GPS (Robert B. Dwork) 2. 01:31 PM - stepping down from the bus voltage (GOLDPILOT@aol.com) 3. 01:34 PM - Lowrance 2000c runs on 5-35 volts DC (GOLDPILOT@AOL.COM) 4. 02:22 PM - Re: stepping down from the bus voltage (linn Walters) ________________________________ Message 1 _____________________________________ Time: 05:13:25 AM PST US From: "Robert B. Dwork" Subject: Re: TeamGrumman-List: Handheld GPS --> TeamGrumman-List message posted by: "Robert B. Dwork" Rich, I can find out for you exactly what was done by the avionics tech. He did NOT use the cigarette power cord supplied with the unit because, as I said, I had to buy a separate data cable, which is a four-wire lead (one power, one ground, and two data connections to the fuel flow meter - which takes info from the Lowrance and tells me how much fuel I'll need to get to my destination, how much reserve I'll have when I get there, and what I'm getting for NMPG ). My statement that the GPS power goes into a jack isn't quite accurate - the jack is there for legality purposes ( as the portable GPS is not considered portable if it is directly hard-wired into the electrical system - so says my avionics tech ) but actually, the power lead from the gps DOES have a direct connection into the system. The "portability" arrives from the ability to disconnect the power cord from the back of the GPS and run it on batteries - for the 30 minutes it'll last). Again, I suggest you might want to call or write Rob Rollision at airplanegear.com with questions about the 2000c- he knows this unit very well. ----- Original Message ----- From: Sent: Saturday, April 29, 2006 11:57 PM Subject: Re: TeamGrumman-List: Handheld GPS > --> TeamGrumman-List message posted by: n32romeo@aol.com > > Yes, but you must use the supplied cigarette lighter plug that provides > the unit with the 6VDC (stepping down from the bus voltage) is my > understanding. I was just wondering what the installer did on Bob Dwork's > Traveler to as he states: "I have mine hooked up through an input jack > into the panel, where it draws power off the bus". I am thinking the > installer must have installed some form of step-down transformer to feed > the unit 6VDC (or installed the cigarette lighter plug behind the panel). > I have a similar issue that I am feeding multiple equipment from the > cigarette lighter. Currently I have the wires going to my portable > intercom and my old GPS spliced together and then plugging into the > cigarette lighter. My intercom needs 12 volts, so this same set-up would > not work with the Lowrance supplied plug. This would be a minor problem > to solve with Radio Shack parts, just need to put together the schematic. > Maybe I am wrong on this. If someone with a 1000 or 2000 could measure > the voltage on the connector going to the GPS out of the cigarette lighter > and let me know if this is bus voltage (12 or 24) or stepped down to > something close to 6VDC, that would tell me what I need to do. > Thanks, > Rich ________________________________ Message 2 _____________________________________ Time: 01:31:54 PM PST US From: GOLDPILOT@aol.com Subject: TeamGrumman-List: stepping down from the bus voltage --> TeamGrumman-List message posted by: GOLDPILOT@aol.com <> You can not use a transformer on DC. Doesn't work that way. You would need to find out how much current the device draws and then calculate the resistance needed to drop X-amount of voltage across the resistor. The rest of the voltage is used by the device. David ________________________________ Message 3 _____________________________________ Time: 01:34:09 PM PST US From: GOLDPILOT@AOL.COM Subject: TeamGrumman-List: Lowrance 2000c runs on 5-35 volts DC --> TeamGrumman-List message posted by: GOLDPILOT@aol.com It's also very possible that there is a small voltage regulator circuit built into the cigarette lighter plug which would output the necessary voltage with any input form 5 to 35 vDC. If the device needs 6 vDC than the supply to the regulating circuit must be at least 6 vDC or a little more. David ________________________________ Message 4 _____________________________________ Time: 02:22:15 PM PST US From: linn Walters Subject: Re: TeamGrumman-List: stepping down from the bus voltage --> TeamGrumman-List message posted by: linn Walters GOLDPILOT@aol.com wrote: >--> TeamGrumman-List message posted by: GOLDPILOT@aol.com > ><of step-down transformer to feed the unit 6VDC (or installed the cigarette >lighter plug behind the panel). >> > >You can not use a transformer on DC. Doesn't work that way. You would need >to find out how much current the device draws and then calculate the >resistance needed to drop X-amount of voltage across the resistor. The rest of the >voltage is used by the device. >David > A lot of the DC>DC converters that plug into a cigar lighter use a linear regulator to drop the voltage ...... while some have a pretty neat (and tiny) switching power supply in there!!! David failed to mention the REASON transformers don't work on straight DC. A transformer needs AC in the primary to cause the magnetic flux in the core to change polarity so those 'lines of force' can cut through the coil in the secondary, and thereby induce the current in the secondary. And for the purists .... yes, you can pulse the DC, but it's crude and inefficient. If you got this far and don't really care .... well, it's too late!!! That's the rest of the story. Linn