8 led battery powered circuit

EGADS!! trying to keep this simple. here is where I think I am headed

Yes, a 74HCxx output will produce only 6mA to 8mA when the output voltage drop is only 0.4V for an old fashioned TTL logic low but is many mA into an LED or load when its output has a few volts of voltage drop.
Look here:

The 330 ohm resistor in your latest schematic can be 150 ohms or less for more brightness until the output current is no more than 25mA.

I need to actually calculate for the 330 ohm resistor but thinking of bread-boarding and adjusting for actual current draw and brightness as the leds I have on hand and ordered a pack of 200 of various colors so trial and error are on the menu. want to stay in the 10 - 15 ma range or maybe lower??

A pack of cheap Chinese LEDs mighty be old dim LEDs in cases that focuses the light into a narrow but bright beam that cannot be seen unless it is aimed directly at you. But high quality modern LEDs are wide angle and bright.
I had a problem using a single resistor on a chaser. The LEDs are lighted one-at-a-time. Then most of the LEDs are not lighted and are reverse biased. Some reverse biased LEDs conduct enough current to cause other turned off LEDs to light.

EGADS!! what is the world coming to with reverse bias LEDs lol
I plan to breadboard the circuit before soldering to a circuit board but thanks for the heads up.
I am looking to build this as cheap as possible as it will only be used one or two nights per month 4 hours per.
hoping I don't have any issues with the leds.
I am surprised Jonsea hasn't jumped in here. Must be really busy.

MrDEB said:

...
I am surprised Jonsea hasn't jumped in here. Must be really busy...

Click to expand...

Why would I? You have plenty of conflicting advice that you'll end up ignoring already.

Now now lol

I don't know.. the overall effect that you want but CD4017's have a high resistance compare to 74HCxx series If you check the drop of (Vcc-Voh)/Ioh =ESR, you will find it equivalent to about 300 Ohms at a 15V and 1k Ohms at 5Vsupply. So you can drive the LEDs directly at 5V but if using 3.6V down to 3V using a LiPo cell, you need a 74LVC04 type buffer which has <50Ohms ESR

I use 10Cd Red Yellow 30 deg 5mm LEDs that are blinding at 20mA and plenty bright at 2mA.

decided to go with a 18F1320 pic. here is a simplified schematic and simple code that appears to work.
objective is if any of the switches are closed thus turning the led connected to the switch on. If any output is on (any led which are toggled to simulate constant on) then RA7 (trigger) is high then RA 6 (flash) is turned on. I breadboarded and after changing the code here and there it all appears to work. NOTE only one led (B0 - B7 then A0 - A1 are turned on sequencly for 1 ms. Was / am contemplating a debounce seeing how C7 is triggered using a 1 ms pulse but havn't seen any real issues.
{

pin 3 does not work??
using 18f1320 so trigger is Ra7 and flash is Ra6

}
'Device = 18F1320
DEVICE = 18F2420
CLOCK = 8

INCLUDE"InternalOscillator.bas"
INCLUDE "SetDigitalIO.bas"
// alias to port pin...
DIM x AS BYTE
DIM I AS BYTE
DIM trigger AS portC.4 // a high triggers portC.5 to flash
DIM flash AS portC.5 // indicates a HIGH on portC.4
// main program...

TRISB = %00000000 AND TRISB // make RB0-RB7 outputs
PORTB = %00000000 AND PORTB // make all LED outputs low
TRISA = %11111000 AND TRISA // make RA0-RB2 outputs
PORTA = %11111000 AND PORTA // make all LED outputs low
setalldigital
INPUT (trigger)
OUTPUT (flash)
trigger = 0
flash = 0
WHILE true

FOR x = 0 TO 7
portB.bits(x) = 1
IF trigger = 0 THEN
flash = 0
END IF

IF trigger = 1 THEN
flash = 1

END IF

DELAYMS (1)
portB.bits(x) = 0
DELAYMS(1)

NEXT
WEND

Tony Stewart said:

I use 10Cd Red Yellow 30 deg 5mm LEDs that are blinding at 20mA and plenty bright at 2mA.

Click to expand...

Could you post the part number of the yellow LED Tony, or a link to the datasheet.

spec

I have about 10k of stock in the garage. 200/bag or so. want some?

Tony Stewart said:

I have about 10k of stock in the garage. 200/bag or so. want some?

Click to expand...

Wow, thanks for the information and the kind offer Tony. Unfortunately I can't do practical at the moment and, as I have probably mentioned before, I am more talk than practical. To me, some of the things that people like Gary350 build are amazing.

At one time, through work, I knew a whole platoon of makers who would actually build my stuff as a hobby, and test it so that was a great arrangement, but no longer since I retired.

A CD ignition system was very popular, especially as it made your automobile pull like a train.

You have 10K of the LEDs. I would have thought you could get a good price for a batch that size.

spec

MrDEB said:

going to build a very simple 8 led circuit that requires very little current draw.
options I am considering are a cd4017 w/ a 7555, 8 leds with aprox. 330 + ohm resistors.
OR
An 18f micro-controller.and resistors ??haven't gone near a pic in a couple of years and wondering if pickit2 is compatible with windows 10??
The pic would perhaps draw less and only one chip.
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??
I am pretty sure I have all the parts of either circuit.
the code for the pic using swordfish should be pretty straight forward, just enable an output for a few milliseconds then onto the next.
This is for the domino game Mexican Train. going to cobble together the center piece from wood with 8 push button switches.

Click to expand...

There is a simple 'zero' current circuit in post #12 here: https://www.electro-tech-online.com/threads/led-chaser-circuit-need-help.149347/#post-1277884 which you may be able to adapt to meet your requirements

spec

I orginally was going to go with the 74hc4017 / 7555 combo but the need for ten leds became an issue plus power consumption.
using a pic allows me to control power consumption via multiplexing and only one chip is required. A project using a micro-controller is just more efficient IMO. As for zero current?? I don't see how it is "zero current"

Am working on the center hub for the "Mexican Train" domino game and how to supply battery power. Have several options:
1urchase a 4- AA battery holder and use a diode to drop to 5v 2000mah
2: use a 3-AAA battery holder I have in my junk box 1000mah
3: use a 4.8v NiMH 1600mah battery pack I have. This is my smallest option and perhaps my best option. If the pack is still good? purchased several years ago.and have a smart charger for it.

MrDEB said:

I orginally was going to go with the 74hc4017 / 7555 combo but the need for ten leds became an issue plus power consumption.
using a pic allows me to control power consumption via multiplexing and only one chip is required. A project using a micro-controller is just more efficient IMO. As for zero current?? I don't see how it is "zero current"

Click to expand...

Yes, a PIC would be more flexible. But you were complaining about complexity and if you use a decent size battery and efficient LEDS I can't see power consumption being an issue.

A small LiIon battery would be 3.5V at 750 ma/hrs giving a duration of 750/20= 37.5 hours with all 10 LEDS on and taking 2mA each. The a verasge would possibly be half of this so the battery duration would be more like 75Hrs.

The circuit I posted does take 'zero' current in practical terms. Of course, that does not include the current taken by the LEDs. That should be fairly obvious.

spec

spec said:

Wow, thanks for the information and the kind offer Tony. Unfortunately I can't do practical at the moment and, as I have probably mentioned before, I am more talk than practical. To me, some of the things that people like Gary350 build are amazing.

At one time, through work, I knew a whole platoon of makers who would actually build my stuff as a hobby, and test it so that was a great arrangement, but no longer since I retired.

A CD ignition system was very popular, especially as it made your automobile pull like a train.

You have 10K of the LEDs. I would have thought you could get a good price for a batch that size.

spec

Click to expand...

ok I'll give you a healthy commission if you find a buyer

complexity in the usage of more than one chip. Using the 74hc4017 would involve three chips.
As for the battery, I have a 4.8v NiMH pack that is listed as 4.8V at 1600MAH
not sure if it is any good. Has never been charged, been sitting in a box for three+ years.
Have a smart charger that hopefully will charge it up??

MrDEB said:

complexity in the usage of more than one chip. Using the 74hc4017 would involve three chips.
As for the battery, I have a 4.8v NiMH pack that is listed as 4.8V at 1600MAH
not sure if it is any good. Has never been charged, been sitting in a box for three+ years.
Have a smart charger that hopefully will charge it up??

Click to expand...

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