Convert 12-14 vdc to 9 vdc for a device only needing 0.3ma...

only one lead.

Sorry, the design must of changed. I got mine about 5 years ago. M-830B. I still have 3 more of them lying around here. I got my hands on a box of them at a grab and give away as part of an event at a meeting.

I looked at your picture, mine does not look like yours. Mine do not have continuity beepers and the fuse is just above the battery and the board goes all the way to the top of the meter covering the LCD..

But it looks the same on every where else how ever except for the color.. Oh well.

If it's a 7106 or 7126 type chip, I think that you can use a 3 resistor divider to measure it's own voltage. But you need to go in and isolate the COMMON virtual ground terminal from the IN-LO terminal.

Theoretically (I never got around to trying this), if your circuit can isolate the IN-LO input (pin 30 on the dip version) from COMMON (pin

The ratio of R(IN-HI,IN-LO) to the sum of the other two resistors is either 1:99 or 1:9 depending on if the circuit is set up with a 100 millivolt or 1 volt reference.

At that low a current, I'd use a zener/resistor for the supply.

meter battery V+

-------+----/\\/\\/\\--+---|

to

he

A simple way to do this that takes less power and is very easy to hook up is to just put an analog moving-coil meter across the battery. You don't need a whole lot of accuracy, since the battery voltage will be a function of temperature as well as state of charge anyway. You can easily expand the scale of a meter by putting a zener diode in series: get a reasonably tight tolerance 10 volt zener, a 100uA meter, and 50,000 ohms of net resistance (including the meter itself), and you have a meter that reads from 10V to 15V, and you should be able to visually resolve to less than 50 millivolts. You can use the meter's mechanical zero to calibrate one voltage accurately, and if your resistance is adjustable, you can calibrate the slope too. Typical current would be 40 to 60 microamps. Doing the same with a

Cheers, Tom

On a sunny day (Mon, 29 Dec 2008 23:20:01 GMT) it happened snipped-for-privacy@eskimo.com (Mark Zenier) wrote in :

I carefully checked if the meter was still reading correctly after that battery test. Did not connect the + lead to the battery -, so was lucky. I have one problem with these meters, the range selection switch looks the same from where the arrow is pointing and 180 degrees opposite. I marked the old yellow one I have with black, but as this one is black I will have to get some special white[?] paint to mark that switch. Already had it on the wrong range several times now. And it should come with a alligator clip, so you can measure one hand versus ground.

Yes, that solution you describe requires 5 extra components. The little DC / DC converter I use has 9 components, but no need to modify the meter. In the late 198X I build a small meter with LCD display with that 7106. The LCD eventually died, but still have the chip and a precision divider. We now live in a time where very complicate things cost next to nothing and are thrown away after use.... So I adapt by thinking modular :-) A typical example, have this setup here with _one_ PIC to drive a LCD, do some IO, have serial com, and use RTS / DTS to control a transceiver (power and transmit). That does not seem reliable, as some serial programs seem to just leave RTS active, or make it active, even if no hardware handshaking is requested. Now I am short of more IO, have no bigger PIC around, but I can replace a HC4053 switch by a similar PIC, one that just listens on the RS232 too, for specific commands, that then sets the control lines for power and transmit. Seems _way_ complicated, but is just software, and that would allow me to omit some other opamp used as comparator too....

.com

That's what I had in mind, but I haven't got too far yet.

I use 1 DC/DC converter and 2 resistors. Should add a zener across the converter input as well. The problem is the 20mA current to run the converter, for on-line monitoring. I have been using it in my car. It reads 14V with engine on and 12V (plus low battery indicator) off. My car battery dies after a few days off anyway.

I also have an AVR driving a LCD and reading the battery. It draws

On a sunny day (Tue, 30 Dec 2008 12:04:57 -0800 (PST)) it happened linnix wrote in :

Yes the PIC (16F690) is also about 2$, 1$62 in a different package:

Turtle wax is more expensive :-). or are you planning large quantities?

harge,

the key no?

If I have my way, it will be in every car battery and dash board. Also, there will be audio input jack and usb power outlet in every junk box (that come with all car) they called the radio. Auto makers are decades behind the curve.

Cheers! Rich

On a sunny day (Tue, 30 Dec 2008 22:53:00 GMT) it happened Rich Grise wrote in :

Ah, yes, it is called Tipp-ex over here, I remembered I had some in the drawer, not used for a hundred years or so (printers and text editors you know), and tried it. It works, but I am not sure how long it will stay white. For now it will do, cool, thank you :-).

On a sunny day (Tue, 30 Dec 2008 12:29:59 -0800 (PST)) it happened linnix wrote in :

I remember Duracell had batteries with an indicator. You could press it, and it would show how much was left in the battery. It was a thermal strip that changed colour, so it emptied the batteries too, increasing sales of course... If you can make it cheap enough it may work., although few people will open their car an look at the battery... In the dashboard.. do the majority of people even know what a battery *is*, and if their car has one ???

I doubt it drew more than, say, 50-100mA, so if the typical test time was 5-10 seconds, unless you were testing your batteries an awful lot, I doubt it measurably increased Duracell's sales. :-)

Apparently Duracell had a patent on the idea though -- which arguably was legitimately novel/non-obvious at the time -- as I remember that Energizer fought back by including a separate, standalone thermal strip tester adhered to the backside of the blister packaging for the batteries.

I think the Energizer bunny is cute, whereas the Duracell bunny just looks creepy.

So does the "Burger King".

tried it.

Harbor Freight sells large marking crayons that are good for filling groves in knobs. I know they have red & yellow, I haven't seen the other colors. They are made to mark steel that needs to be cut, machined or welded. Another choice is the paint pens used by junkyards to mark the year & model on body parts.

Sure it is, but Turtles look great with a high shine! Not only that, but they don't move very fast, so you are finished before they can get away. Just like using flea spray on British Donkeys. ;-)

--

aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in your account:

There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you're crazy.

I have a suspicion they might have made him creepy on purpose, to try to appeal to a younger crowd.

I'd prefer it if they working on improving their french fries' taste to something a little better than "salty cardboard."

I rarely eat there. Maybe once every couple years. For their prices I can fix a nice meal at home. The last few times I ate there, I was helping a small Christian business with computer networking problems, and they 'treated' me to lunch for the help.

BTW, I didn't have to install that printer under Linux on the PC. It died while I was talking to you about the administrator password, so I dug up another PC. The Mandiva Linux install was trashed, and wanted the CD-ROM.

I got a strange letter from the VA the other day. My VA disability papers state that I will never be able to work again, yet I am not classed as unemployable. WTH?

Yeah, fast food is definitely not particularly cheap.. heck, their prices often aren't even that much less than inexpensive mom-n-pop diners, some of which are quite good.

I've actually switched to Ubuntu myself here... I'm sure it wouldn't mind a new install of that. :-)

The government's left hand doesn't know what it's right hand is doing, as usual.

---joel

oo,

en

Even my wife knows about the car battery, but nothing else. My corolla has analog meter, but difficult to tell the exact reading. Her Luxus does not even have analog meter. After her last dead battery, she is well informed about monitoring the voltage. My meter plugs into the cigarette socket. She will let me know if the reading is below 11V. Just to be sure, I would probably wire a three color led based on the battery voltage. She wouldn't ignore it if the color turns yellow or red.

Yuasa makes car batteries with a charge indicator. One of the caps has a built in hydrometer and some optics. that change colour when discharged and (a different colour) for low electrolyte.