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How to build a cheap LED voltmeter | 17 comments (17 topical, editorial)
Re: How to build a cheap LED voltmeter (3.00 / 0) (#11)
by johnlm on Wed Dec 22nd, 2004 at 02:57:10 PM MST
(User Info)

if you ar going to use the meter to control things ths looks ok.  if you want to measure voltage, you can get a digital (cheap one but seems to work fine) from harbor frieght for $8.00.  I got one on sale at $3.99.  Compared it to my two good HP meters and found it was off about 0.5% on the dc volts setting.  Opene it up and adjusted a trimpot to read the same as my HP's.  Not a bad meter for 4 bucks.
Johnlm



Re: How to build a cheap LED voltmeter (3.00 / 0) (#14)
by troy on Fri Dec 24th, 2004 at 10:37:34 AM MST
(User Info)

I have half a dozen of the HF cheepie meters and a nice Fluke for precision work.  I did make a discovery about the Harbor Freight meters that could affect your use of that meter.  They apparently don't have any means of compensating for a low 9V battery.  And I have gotten into trouble on my big battery bank by using readings that were 3V high because of a low 9V battery in the meter.  The low battery indicator was not on at the time the error occured.

Also, some of the recent HF meters have a lighted display available with a switch.  I discovered that turning the light on caused a big change in the indicated voltage, so if you have one, don't use the light while reading anything that matters.

Not saying they aren't useful, just saying to throw away the cheap battery that came with it immediately, and make sure to have a fresh battery in there regularly.

Good luck and have fun!

troy

[ Parent ]



Re: How to build a cheap LED voltmeter (3.00 / 0) (#16)
by BT Humble (bt_humble@bigpond.com) on Tue Jan 4th, 2005 at 02:43:10 PM MST
(User Info) http://www.humbletown.org


if you ar going to use the meter to control things ths looks ok.  if you want to measure voltage, you can get a digital (cheap one but seems to work fine) from harbor frieght for $8.00.  I got one on sale at $3.99.  Compared it to my two good HP meters and found it was off about 0.5% on the dc volts setting.  Opene it up and adjusted a trimpot to read the same as my HP's.  Not a bad meter for 4 bucks.

Basically my reasons for using this rather than a cheap digital meter are the same as listed here:

http://www.homepower.com/files/bat-o-meter.pdf

Essentially, you don't have to keep replacing 9V batteries in this one, and you can tell from the other side of the room if your battery is getting low (without having to refer to a chart of voltage levels).  Less is more! ;-)

BTH

[ Parent ]



How to build a cheap LED voltmeter | 17 comments (17 topical, 0 editorial)

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