Simple Battery Charge Indicator from EDN

This is a nifty idea to indicate battery charge with a simple circuit.

EDN Battery Charge Imdicator

Visitor said:

This is a nifty idea to indicate battery charge with a simple circuit.

**broken link removed**

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As long as you can write code and have the tools to program the PIC....

eTech said:

As long as you can write code and have the tools to program the PIC....

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Actually, the code is available. The same limitation applies to any microcontroller, no? But to me, the important part is the idea. It can be implemented using whatever technology you like.

Visitor said:

the important part is the idea. It can be implemented using whatever technology you like.

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Yes.
You could use an LM3914 with no programming, programmer, or programming tools required.

Geez. Not-invented-here syndrome much?

It's an idea. Something to think about. It's one approach to solve a problem. Maybe you take away something useful. Maybe you don't. If it results in something that works for you, great. If not, move along. You don't have the imagination to see anything here.

If you use an LM3914, you would be challenged to achieve results with anywhere near that current draw of the suggested circuit.

I have the imagination to see how to do the same job in different (and possibly simpler) ways.
Do you?

Sorry for sharing something that might be useful to some people here.

I didn't realize that taking space from gsry350's fifteenth thread about flashing LEDs on carbon-zinc batteries, MrDEB'S hundredth tread about copy&pasting software he doesn't understand didn't work again or the fortieth post this week about replacing a cratered smt part using a Weller Solder Gun probably isn't going to fix whatever device would be such an issue.

crutschow said:

Yes.
You could use an LM3914 with no programming, programmer, or programming tools required.

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crutschow said:

I have the imagination to see how to do the same job in different (and possibly simpler) ways.
Do you?

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The PIC solution has uA draw in sleep mode between readings while the LM3914 draws 3mA in standby mode and you'll need additional circuitry to toggle it between enable and standby.

I wouldn't use a $3.70 device (LM3914) at end of life only available in a 20PLCC SMD package when you can do it with a 6-pin device at $0.60 with fewer external components? Writing the code is minimal and any microcontroller can be used - more of a concept than a single solution.

I understand that $3 isn't much difference but the LM3914 is a rather special chip - I have a tube of 10 sitting in a drawer and never bothered using them - kind of a special device. I even have a stack of the earliest version LM3914 sold as a module by National Instruments with the 10 mounted LEDs and I haven't found a use.

I also have a drawer of $0.60 PICs for such things and find them to be much more useful.

I like the idea Visitor found. I like discussing all ideas - even the LM3914. Ideas are a good way to keep fresh by looking for new ways to skin cats.

There are obviously many ways the three LEDs with different forward voltages can be used to make a voltage sensor. It doesn't have to specifically be a PIC, even a low duty cycle cmos555 could be used to flash at a given rate for a given duration.

Looking at the graph in www.batteryuniversity.com , a lithium battery reaches its fully charged voltage of 4.2V per cell long before it is fully charged because it is still drawing charging current. Its current drops to a low amount when it is fully charged.

Gophert;
I very much Like your “outside the box” idea, showing the battery’s state of charge by changing the flashing LED’s frequency.
It would further reduce parts count and possibly current consumption.
The nice thing with a microcontroller is that one could easily change the code until one finds a pleasant effect.

Another out of the box idea with a single LED: change the number of flashes depending on the charge. For instance, three flashes-pause-three flashes for a fully charged battery.
Single flash-pause-single flash for a discharged one.

schmitt trigger said:

Gophert;
I very much Like your “outside the box” idea, showing the battery’s state of charge by changing the flashing LED’s frequency.
It would further reduce parts count and possibly current consumption.
The nice thing with a microcontroller is that one could easily change the code until one finds a pleasant effect.

Another out of the box idea with a single LED: change the number of flashes depending on the charge. For instance, three flashes-pause-three flashes for a fully charged battery.
Single flash-pause-single flash for a discharged one.

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The tough part with programming means the microcontroller needs to measure state of charge but that specific micro has no internal or external voltage reference - vdd is always full scale regardless of battery charge. So one ADC channel will need a voltage reference and one measure the battery voltage, then flash any of the lights as needed. The LEDs could be arranged in come "charlieplexed" format to optimize useage of the four I/o pins and ADC.