Measuring voltage with seven segment display - Page 1
Forum section: electronics / projects

author: vigsgb
author_rank: Contributor
timestamp: January 30, 2014, 12:45:36 am
content: I want to measure voltage from a seven segment display and have no idea where to start. Do I need a micro with a voltage reference and a power shunt? I want to eventually build a power supply with a display and am researching how to achive each of the functions I came up within my spec. Just need a little nudge in the right direction.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 30, 2014, 01:11:04 am
content: Buy some cheap Harbor Freight meters and permanently mount them in your project. Power them from small isolated bias supplies.

author: vigsgb
author_rank: Contributor
timestamp: January 30, 2014, 01:14:32 am
content: Quote from: NiHaoMike on January 30, 2014, 01:11:04 amNever thought of that and I can get them for free with a coupon.

author: Smokey
author_rank: Super Contributor
timestamp: January 30, 2014, 01:18:04 am
content: http://www.futurlec.com/Panel_Meters.shtml

author: Macbeth
author_rank: Super Contributor
timestamp: January 30, 2014, 03:01:54 am
content: Loads on ebay for dirt cheap from China. I recently ordered 5 of these just becausehttp://www.ebay.com/itm/360732171649?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: January 30, 2014, 03:28:32 am
content: I've wanted to see something like this on a meter.http://www.alibaba.com/product-gs/840661556/bcd_e_paper_e_ink_display.htmlHigh resolution (VGA, SVGA, XVGA or even higher)Extreme wide viewing angles (nearly 180°)Wide operating temperature rangeExceptional sunlight readabilityVarious color combinationsZero power consumptionI don't know the performance of these and if the performance data's on that page I don't know how to read it.This one's more.http://www.alibaba.com/product-gs/941552859/e_ink_display_Bi_stable_Cholesteric.html

author: rdl
author_rank: Super Contributor
timestamp: January 30, 2014, 03:31:39 am
content: Do some shopping though if you decide to get some of those little meters off eBay. They come in several varieties. There are versions that can measure voltages other than their own supply, there are 4 digit versions and you can get them in various LED colors.

author: Macbeth
author_rank: Super Contributor
timestamp: January 30, 2014, 06:08:00 pm
content: Just received mine - quite cute and nice and bright. I'm measuring a 3.7V Li-ion battery here. Pound coin for scale.Trimmer on the back to calibrate.

author: owl_uk
author_rank: Contributor
timestamp: January 30, 2014, 09:44:15 pm
content: Where did you buy it from in the end? ebay?

author: Macbeth
author_rank: Super Contributor
timestamp: January 31, 2014, 01:14:36 am
content: Quote from: owl_uk on January 30, 2014, 09:44:15 pmYup! See me previous post for link - there are many others, slightly more expensive for blue/green, etc. Also, this type of meter is powered by the source so needs at least 2.5V, and enough current to drive the LEDs. Plenty more can be got where you can provide an external PSU and so measure lower volts.It seems trivial to me to adapt or modify these to do just that and also display current instead of volts.PS. The display was wobbling between 3.77-3.78, while my calibrated meter measured 3.768, so not bad at all for what it is. The trimmer can be nudged I am sure.

author: LukeW
author_rank: Frequent Contributor
timestamp: January 31, 2014, 03:13:44 am
content: Quote from: Macbeth on January 30, 2014, 03:01:54 amCool. Do you know if they make similar ammeter versions of those? Or even millivolt-scale voltmeter ones suitable to go across a current shunt?