4-1/2 digit panel meter

A man with one voltmeter knows his voltages. Perfectly. When, due to the pressures of circumstances, he acquires one more, he doesn't, any longer. Each meter will have its own interpretation of the voltage presented to it, and this can cause confusion when relying upon them to perform critical tasks such as charging Li-Po batteries.

This instructable describes a Four-and-a-half digit voltmeter based on the MAX1498 ic from Maxim. It comes calibrated from the factory and all you need to do is to add the components to supply power to it, and to display the output from it.

With four and a half digits, this meter can display counts upto 19999, plus or minus. The "and half" part of the designation comes from the fact that the first display, used to indicate the sign (+ or -) can, without much effort, be used to display a "1" as well.

Since most multimeters used for servicing are of the three and a half digit variety this little circuit can be used to keep a bunch of them agreeing with each other.

Calibration is free, comes with the chip, built in, so as to speak, and does not depend upon any external components you connect to the chip.

Step 1 Getting the parts together

Apart from the MAX1498 chip and five seven segment common cathode displays, there isn't much to acquire. The other stuff needed can easily be pulled off any hard drive board.

Comments

[throbscottle]

I've never heard of etching with saltwater. Could you please elaborate on this?

[Roughrider59]

Webmaster, the thumbnails don't enlarge when clicked.

[mariosk8s]

Where did you acquire the max1498. I seem to have a hard time finding them online for quantities under 1000. I was hoping to get maybe 5 of them.

[neelandan]

Maxim will send you two pieces free if you just ask.

[babu03]

NO PARTS LIST/BILL OF MATERIALS !

[neelandan]

Since I was using recycled components, this prototype has an abundance of decoupling capacitors and unnecessary wiring. If you are interested in manufacturing this thing, you are best advised to go to the manufacturer's web site to look at the datasheets and other recommendations regarding assembly

[cloner]

forgive my question but this one reminds me of my counter project. if this were a push button queue counter for clients, how can u make the push button counter to have a 3-second delay? tnx :)

[benjamenjohnson]

I might be wrong, but I cannot find any reference to the 1498 being calibrated at the factory. You are using the internal voltage reference which can vary anywhere between 2.007V and 2.089 with 2.048 being the nominal voltage. I see that it has offset calibration but that can't be confused as span calibration. If your reference voltage can vary +-2% then your measurements can off be 2%. This only gives you about 3 digits of accuracy Still this is a very cool part and project.

[chavez00001]

Cool, Another one of those Kick Butt PCB board designs