8 led battery powered circuit

[JonSea]

Tony's LEDs remind me of my yellow 7-segment LED digits....

I had 15 boards assembled in China that each used 3 red 7-segment digits and 3 yellow 7-segment digits. The company had nice red digits and I asked them to use the same Digit in yellow. They couldn't find a source of the yellow digits. To get the 45 I needed, the option was to buy a thousand from the factory.

The options were to ship 45 of the LiteOn digits I had been using to China (which it turns out aren't nearly as good as the digits my supplier could get in China) or go with a smaller Digit that fit in the same footprint. Sending the 45 would cost almost as much as buying a thousand, and if I had more boards assembled their in the future, I'd face the same problem again. Buy the thousand and save the remainder for future use.

That was a year ago, and that project is creating along. I just had another board assembled there, and I asked them to send the remaining digits back to me.

But on reflection, I had absolutely no use for nearly a thousand LED 7-segment displays. Better to have them retain them in case that project ever does take off in a big way. They are of more value to me waiting in China for possible use than taking up space in my office.

 

[JonSea]

Why would a 74HC4017 involve three chips- I think two.

A smart charger will not touch your battery if the terminal voltage has got too low. Simply put some current into the battery until it gains some voltage. You may have to use a high voltage (20V to 40V) to punch through any crud that may have formed in the battery. Do it via a resistor to limit the current. 4.8V will be fine for the circuits mentioned on this thread.

If that does not work you may need to flash the battery but that is another story.

spec

Given MrDEB's success with projects, doing anything to a lithium-ion battery other than connecting it to a safe charger is ill advised. Flash indeed is the probable result.

 

[spec]

Given MrDEB's success with projects, doing anything to a lithium-ion battery other than connecting it to a safe charger is ill advised. Flash indeed is the probable result.

 

[MrDEB]

I monitored the battery voltage while charging and never went higher than .7 volts. Kept unpluging the charger and all of a sudden the red charging light went on and stayed on. Battery voltage w/ charger connected measures 6.5 volts. Looks like it started charging. After about 90 minutes the green led has come on. it might have charged up but need to check voltage with charger disconnected. As for the 74hc4017 needing three chips = 2 - 74hc4017's and 1 - 7555

 

[spec]

I monitored the battery voltage while charging and never went higher than .7 volts. Kept unpluging the charger and all of a sudden the red charging light went on and stayed on. Battery voltage w/ charger connected measures 6.5 volts. Looks like it started charging. After about 90 minutes the green led has come on. it might have charged up but need to check voltage with charger disconnected. As for the 74hc4017 needing three chips = 2 - 74hc4017's and 1 - 7555

Got it about the number of chips.

Sounds like your battery is two LiIon cells in series, from a camera perhaps. If so, the terminal voltage static should be (UPDATE) 2 * 3.6V =7.2V at 25 Deg C. But see MrDEB & AGs following posts #46 & 47.

Now that you have some charge in your battery, leave it charged for 24hrs and then discharge the battery and recharge it a few time until the batter capacity increases.

spec

 

[MrDEB]

the battery pack is 4 cells for 4.8 volts BUT I measured the packs output voltage at 5.57 volts!
these are NiMH batteries, not li ion.
looking at adding a diode on my circuit board to reduce the battery voltage to 4.5 aprox.
NOTE the battery pack has never been charged or used before so voltage migh just be an anomaly??
NiMH batteries will self discharge according to battery research I have done.

 

[audioguru]

A Ni-MH battery cell is fully charged at about 1.4V so your pack has 4 cells. At half discharge time it averages 1.2V per cell.

Why two 74HC4017 ICs? For 20 LEDs?

Why worry about power consumption when a 4017 or the HC kind lights only one LED at a time? Then at 2mA of LED current a 750mAh battery will last for 750/2= 375 hours which is more than 15 days and nights non-stop.

 

[MrDEB]

Very true about the 74hc4017 but I only am using ten LEDs and each 74hc4017 has only 8 outputs.
I purchased two 74HC4017's and two 7555 chips off ebay to use but ran across a lone orphan 18F1320 in my junk box and it needed a home. LOL
A pic is way more fun to use and efficient with board real estate. one board, one 18 pin chip plus I can alter my multiplexing to change the current draw slightly.
My big concern now is enclosure issues. I want to be able to change-out a switch or LED if needed but making the unit dissemble-able.
Plus how to make battery charging easy without taking the whole unit apart.
Will take some pictures today.

 

[spec]

Very true about the 74hc4017 but I only am using ten LEDs and each 74hc4017 has only 8 outputs.
I purchased two 74HC4017's and two 7555 chips off ebay to use but ran across a lone orphan 18F1320 in my junk box and it needed a home. LOL
A pic is way more fun to use and efficient with board real estate. one board, one 18 pin chip plus I can alter my multiplexing to change the current draw slightly.
My big concern now is enclosure issues. I want to be able to change-out a switch or LED if needed but making the unit dissemble-able.
Plus how to make battery charging easy without taking the whole unit apart.
Will take some pictures today.

The 74HC4017 has ten outputs

Accessibility and battery charging are easy to do.

spec

 

[MrDEB]

charging the battery is easy, its figuring out where to mount the charging pug on the project.
my bad on the # of outputs on a 74hc4017.
the basic electronics are done except to add a diode on my power rail to chop the 5.5 to 5v or less. Even considered the battery condition monitor that some pics have onboard but that's getting tooo carried away and not even sure the 18F1320 has it on board anyway.

 

[JonSea]

Looking at your schematic and trying to understand your code, is the end result:

If switch n is closed, LED n is illuminated? No other function besides that?

 

[spec]

charging the battery is easy, its figuring out where to mount the charging pug on the project.
my bad on the # of outputs on a 74hc4017.
the basic electronics are done except to add a diode on my power rail to chop the 5.5 to 5v or less. Even considered the battery condition monitor that some pics have onboard but that's getting tooo carried away and not even sure the 18F1320 has it on board anyway.

Battery charging just amounts to sticking a two contact plug on the unit, into which a standard battery charger can connect.

The universal rule for accessibility is to mount the electronics on a board (printed circuit or otherwise) with four cheeks: front rear and two sides. You then have top and bottom covers. This allows access to all components. The Japanese made extensive use of this approach with their equipment designs, starting in the late 1960s.

Failing the four-cheek construction above, and all you have is a standard box with a lid, mount all the electronics to the lid and not in the box where it would be buried in a pit The box then effectively becomes the lid and has no connections whatsoever to the electronics on the lid, which has all connectors switches etc fitted to it. This allows you to remove the base of the box easily and, if the layout of the electronics on the lid has been well thought out (all I/O connections along one edge of any PCB), allows reasonable access all components.

The biggest failure of getting home-brew electronic projects operational is lack of accessibility. Remember the adage: 'Never mind how simple and insignificant a component, even be it a humble washer, it is bound to fail if inaccessible.'

spec

 

[audioguru]

I am confused. The first two pages of this thread used one 74HC4017 driving only 8 LEDs so two of the outputs were not used. A comment was made that all 8 LEDs will draw a high current so low current LEDs should be used but a 4017 has only one output turned on at a time and NEVER has all outputs turned on so the current is not much. Then the number of LEDs was increased to 10. Then a PIC will replace the electronics?

 

[Tony Stewart]

These types of "circular " discussions always stem from newbies who don't know how to define all requirements up front and then change implementation which was specific to the question, wasting a lot of "good bandwidth " in the discussion.

 

[JonSea]

....going to build a very simple 8 led circuit that requires very little current draw....going to multiplex the leds to save on current draw.....Each led will have its own switch. when a switch is ON the corresponding led will appear to be on steadily or maybe flash??.....

Going back to MrDEB's original post, he wants 1 - 8 LEDs on, the state of each controlled by a switch.

Multiplexing is part of the circuit "to save on current draw".

I think you've been led down a MrDEB rabbit hole.

Multiplexing is done to save connections on things like 7-segment or dot matrix displays, not to reduce power consumption.

Say an LED has satisfactory brightness when operated at 10mA. If you mux that LED with 7 others, it will have to be driven much harder(~8x?) to appear the same brightness because it's only illuminated 1/8 of the time.

 

[MrDEB]

To clear things up. I originally was going to use the 4017 idea which would have achieved the same end result as using the pic but using more components with the 4017 circuit.Just the 7555 would add two capacitors and two resistors. Using the pic I should use a cap on the power rails.
The pic has more outputs but only need 10. This is a KISS circuit.
As for enclosure, it is made of a 10 x 14 inch MDF board with a 3 x 5 cutout in the middle then two 1/4" thick plywood for top and bottom with a laminated picture of a locomotive and a tiny led for the headlight. To charge the battery I need to mount a female plug on the outside but isolating the charger from the pic circuity is an issue I need to look at.
At this point of assembly I have all ten push buttons and leds mounted but still need to address an ON OFF switch and method to charge up battery without taking the entire assembly apart. I may just add a small door on the bottom to access the battery. Unplug it then charge it up.
Need to address circuit board mounting as well.