5V isolation - Page 1
Forum section: electronics / beginners

author: niekproductions
author_rank: Contributor
timestamp: October 07, 2013, 02:02:03 pm
content: I have a panel current meter that requires 4-10V DC and an isolated ground. I'd like to power it from the battery it's measuring, how would I go about isolating it?I thought about using a 1:1 transformer, but I couldn't find one in my junk bin.

author: Simon
author_rank: Unknown
timestamp: October 07, 2013, 02:10:45 pm
content: you can't use a transformer on a battery or any DC current. why must the ground be isolated ? are you sure about this ?

author: niekproductions
author_rank: Contributor
timestamp: October 07, 2013, 02:24:59 pm
content: Quote from: Simon on October 07, 2013, 02:10:45 pmI am sure about it. The meter uses a shunt. When I power the meter from the same battery I'm measuring, it shorts out.

author: Rigby
author_rank: Super Contributor
timestamp: October 07, 2013, 02:35:37 pm
content: Back up. What are you trying to do? What's your goal? You're trying to measure the battery with a device powered by that same battery. Why?

author: niekproductions
author_rank: Contributor
timestamp: October 07, 2013, 03:38:11 pm
content: Quote from: Rigby on October 07, 2013, 02:35:37 pmOkay,I have a robot. Inside, it has one 7V lead acid battery. I purchased a panel current meter with four wires: two for high-side current measuring and two for the meter's power. Because the grounds are connected together and it's on the high side of the battery, it will short out via the shunt.I don't have enough space to fit a second (small) battery.

author: MinK
author_rank: Contributor
timestamp: October 07, 2013, 03:39:08 pm
content: Try to power your measurement gadget from separate battery or you can use insulating DC-DC converter. I guess nn2-05s05s might work.or maybe you can use other measurement device, some sort of analog-digital converter. Micro controller typically has analog digital converter embedded.

author: andtfoot
author_rank: Unknown
timestamp: October 07, 2013, 03:45:14 pm
content: You can't just connect the shunt on the other side of the load so the grounds are common?

author: zapta
author_rank: Super Contributor
timestamp: October 07, 2013, 04:05:29 pm
content: Can you provide a link to the datasheet of that panel meter?

author: niekproductions
author_rank: Contributor
timestamp: October 07, 2013, 04:31:06 pm
content: Quote from: andtfoot on October 07, 2013, 03:45:14 pmDoh!Quote from: zapta on October 07, 2013, 04:05:29 pmIt's this meterhttp://www.adafruit.com/products/574.I don't know why I decided to wire it on the high side.. Probably why I posted it in 'Beginners'

author: WarSim
author_rank: Frequent Contributor
timestamp: October 07, 2013, 04:35:48 pm
content: Relay

author: Unknown
author_rank: Unknown
timestamp: October 07, 2013, 06:22:49 pm
content: Quote from: niekproductions on October 07, 2013, 04:31:06 pmFrom that page:QuoteQuote from: WarSim on October 07, 2013, 04:35:48 pm

author: Janaha
author_rank: Newbie
timestamp: October 07, 2013, 08:52:30 pm
content: Hy.Sorry, you already buyed that pannel meter like me. I felt in the same bug hole and i also have some of the lying around here.I learned that i must search for a pannel meter that supports a common ground. I found some on ebay, but they a a bit pricier than those simple pannels without the ability to share a common ground. ( The searchterm i used to find these is : panel meter common ground )I just locked on ebay and found those here as an example.eBay auction: #220918151290Those pannels are working even in those situatios where you whant to have them sharing a common ground with the "power" you want to measure.GreetingsJanaha

author: Unknown
author_rank: Unknown
timestamp: October 07, 2013, 08:57:14 pm
content: Did you actually read the Adafruit page?

author: niekproductions
author_rank: Contributor
timestamp: October 08, 2013, 12:25:54 pm
content: Quote from: alm on October 07, 2013, 08:57:14 pmI bought the thing from a reseller, so I didn't see thatQuote from: alm on October 07, 2013, 06:22:49 pm

author: zapta
author_rank: Super Contributor
timestamp: October 10, 2013, 05:13:00 am
content: The adafruit page has this schematic that shows how to measure low side current while powering the meter and the load from the same DC supply.It is similar to these kind of in series meters that are popular with remote control models.http://www.rcgroups.com/forums/showthread.php?t=311574