Looking for low power battery voltage indicator - Page 1
Forum section: electronics / projects

author: deephaven
author_rank: Frequent Contributor
timestamp: May 28, 2012, 08:39:18 am
content: I was looking for a low power battery voltage indicator. My electric toothbrush has an LCD on it to do this function, but I can't find anyone selling anything similar so I guess this is a custom design.I'm not looking for a 'fuel gauge' necessarily, just a voltage level would do.

author: Psi
author_rank: Super Contributor
timestamp: May 28, 2012, 10:31:18 am
content: Probably not the sort of low-power you want, but could be used with a push button to active the chip and display the voltage.

author: deephaven
author_rank: Frequent Contributor
timestamp: May 28, 2012, 11:25:45 am
content: Thanks for the link.I need an indicator that is permanently displaying rather than having the user do anything. So the display device needs to be inherently low power.

author: T4P
author_rank: Super Contributor
timestamp: May 28, 2012, 11:59:51 am
content: A LCD Bargraph ? They do that and it's definitely customYou can use the 10seg led bargraphs and the LM3914 if you don't mind

author: Psi
author_rank: Super Contributor
timestamp: May 28, 2012, 12:34:01 pm
content: While i love the LM3914, the problem for his application is power consumption. The chip draws a few mA while doing nothing.So it would run his battery flat if it was active all the time.

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 28, 2012, 09:38:04 pm
content: Here's your LCD:[url=http://www.excel-display.com/bargraph.shtml]http://www.excel-display.com/bargraph.shtmlAnd here is a possible driver:http://www.datasheetcatalog.org/datasheet/philips/HEF4754VD.pdfNot sure what you think is "low power" and what resolution you want, but yeah, it's available.

author: free_electron
author_rank: Super Contributor
timestamp: May 28, 2012, 11:33:01 pm
content: http://www.digikey.com/product-search/en/optoelectronics/display-modules-lcd-oled-character-and-numeric/524437?k=lcdpick an lcd display, drive from an ultra low power microcontroller. like an str8. St has lcd scanning code available. draws microamps...

author: vk6zgo
author_rank: Super Contributor
timestamp: May 29, 2012, 04:01:17 am
content: They call them moving coil meters!A small analog meter won't draw a lot of current,& you can usually find extremely tiny ones in junk pieces of equipment,where they were used as audio level meters.I think most of them are around 50uA FSD (but you can set a lower scale reading if that is too much!)You may have to mess around with series resistors to get what you want.Obviously,this is what you would use for a "one off" project,& if you are making thousands they may be hard to get in those quantities.The other thing you can do,is teardown your toothbrush & steal the LCD!!

author: T4P
author_rank: Super Contributor
timestamp: May 29, 2012, 06:06:24 am
content: MSP430 can be a good candidate along with a small lcd (not graphic but those blue-on-green screens) screen

author: deephaven
author_rank: Frequent Contributor
timestamp: May 29, 2012, 08:25:08 am
content: Quote from: free_electron on May 28, 2012, 11:33:01 pmThanks for the suggestion. They are still a bit bigger than I was hoping for.

author: deephaven
author_rank: Frequent Contributor
timestamp: May 29, 2012, 08:27:00 am
content: Quote from: vk6zgo on May 29, 2012, 04:01:17 amWe plan to make a few hundred of these, so I don't want to end up with 100's of toothbrushes - especially if you can't read their battery status