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8 led battery powered circuit

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MrDEB

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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.
 

spec

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Just one point: if you multiplex the eight LEDS you will only need a single resistor.

spec
 

MrDEB

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very true only need one resistor.
if using a pic then fewer resistors are needed as well.
still need to unpack all my electronic stuff and configure my lap top to run pickit 2.
 

audioguru

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Most Helpful Member
Very little current draw for LEDs means that they will be very dim. If your blink the LEDs for 30ms every second then their average current is 1/30th than if they are continuously lit.
I made some LED chasers with 74HC4017 ICs and blink each LED brightly for 30ms plus a 2 seconds pause after a few chases. 2 or 4 AA alkaline cells operate a chaser for 3 months continuously. The HC version has much more output current at low supply voltages than the regular CD4017.
 

MrDEB

Well-Known Member
if I use a 74hc4017 then maybe I won't need a voltage reg? need to research.
have a schematic using an 18f pic but not sure of voltage and parts needed.
using a pic = 1- pic, 1 resistor, 1- voltage reg, 8 leds, 8- switches for leds and 1- ON/OFF switch plus various caps for power supply and pic
using a 74hc4017 = 1 74hc4017, 1 - 7555, 8 leds, 8- switches for leds and 1- ON/OFF switch plus various caps for the 7555
time for more research
 

be80be

Well-Known Member
You don't need a voltage regulator if you run the pic with 3 AA batteries
Oh good to see you Mrdeb
Oh and you could use 4 AA and a diode to drop the 6 volts but that a waste of power I'd run it at 4.5 volts and use high bright reds leds.
 

MrDEB

Well-Known Member
lots of options for sure.
I see ol be80be is still around. I myself have yet to unpack all my electronic stuff but I did get a work area in my laundry room set up.
I was thinking of using a zener diode for voltage source as an option. everything is better with micro-controllers-- that's what I hear lol
using the 74hc4017 adds more parts as a 7555 is called for where as the pic doesn't need it.
my concern is the pickit2 and windows 10
 

be80be

Well-Known Member
Oh and the pickit 2 software works great on windows 10 most everything works good i have no problems just driver signing which is easy to turn off but that was only with using hid cdc drivers for the 18f2550.
The pickit2 works great
 

MrDEB

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I have a schematic but photobucket is really slow this morning.
maybe draw out on using a 4017/7555 just for the practice as I haven't done any electro stuff in a long time. except the sound generating project that I need to dig for resistors etc.
As for using a Pic, yes they are more bang for the buck as well as being more fun
 

audioguru

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My LED Chasers do not have voltage regulation. When the LEDs become dim and the battery cells are about 0.7V each after 2 months then I replace the battery. I do not use Cmos 555 oscillators, instead I use a 74HC14 Cmos hex (6 of them in a package) Schmitt Trigger inverters and one inverter makes an oscillator. I use 2 diodes with an inverter to make a Mickey Mouse logic gate. HC logic ICs work down to a very low supply voltage with plenty of output current.

Here is a Schmitt-Trigger oscillator made with one inverter (posted directly to this post here and not over at Photobucket):
 

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MrDEB

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will try and upload the jpeg file that I increased the resolution to 300dpi and converted to jpeg with a white background.
I like your idea of just using 4 AA batteries and a diode to get the 5v. Would save using the 7805
mexican train.jpg
 

MrDEB

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one thing about using a 74hc4017 is it will output a max of 8ma I think??
pretty dim leds
 

audioguru

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Most Helpful Member
one thing about using a 74hc4017 is it will output a max of 8ma I think??
pretty dim leds
With a 5V supply, an ordinary 4017 has an output current to an LED of typically only 3mA (very dim) but a 74HC4017 will produce more than its maximum allowed output current of 25mA. My chasers use a resistor to limit the LED currents from the 74HC4017 to 23mA and they are very bright.

EDIT: My chasers with 2V red LEDs use a 3V 2-cells battery but my chasers with 3.2V multi-color LEDs use a 6v 4-cells battery.
 

audioguru

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I like your idea of just using 4 AA batteries and a diode to get the 5v. Would save using the 7805.
A 7805 needs a minimum input of 7V that you certainly will not have when your 6V battery voltage drops to 3V. If you do not use the 7805 the PIC will get only (3V - 0.7V from the diode=) 2.3V so it also will not work.
 

MrDEB

Well-Known Member
now I am lost
going by this page http://www.allaboutcircuits.com/textbook/digital/chpt-12/ring-counters/
and the discussion about johnson ring counters
"The above Johnson counter shifts a lighted LED each fifth of a second around the ring of ten. Note that the 74HC4017 is used instead of the ‘40017 because the former part has more current drive capability. From the data sheet, (at the link above) operating at VCC= 5V, the VOH= 4.6V at 4ma. In other words, the outputs can supply 4 ma at 4.6 V to drive the LEDs. Keep in mind that LEDs are normally driven with 10 to 20 ma of current. Though, they are visible down to 1 ma. This simple circuit illustrates an application of the ‘HC4017. Need a bright display for an exhibit? Then, use inverting buffers to drive the cathodes of the LEDs pulled up to the power supply by lower value anode resistors.

The 555 timer, serving as an astable multivibrator, generates a clock frequency determined by R1 R2 C1. This drives the 74HC4017 a step per clock as indicated by a single LED illuminated on the ring. Note, if the 555 does not reliably drive the clock pin of the ‘4015, run it through a single buffer stage between the 555 and the ‘4017. A variable R2 could change the step rate. The value of decoupling capacitor C2 is not critical. A similar capacitor should be applied across the power and ground pins of the ‘4017."

If the 6v leds are bright then perhaps the 74hc4017 is the ticket. I need to draw up a schematic
 

spec

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one thing about using a 74hc4017 is it will output a max of 8ma I think??
pretty dim leds
If you use low current, high brightness LEDs they will be pretty bright with only 1ma to 2mA average current. If you Mux eight LEDs with 16mA, the average current through each LED will be 2mA.

If you use a single LiIon battery, say a CR123, and a PIC running around 4Mhz all you would need is a decoupling capacitor for the supply line.

You could make a Rolls Royce system by replacing the LED current limiting resistor by a constant current generator so that the LEDs would remain at constant brightness with changes in battery voltage (update 2016_09_25: LiIon rechargeable batteries tend to have a more consistent voltage and lower ESR throughout there useful operating charge than normal non-chargeable batteries).

You could then get fancy and have the PIC tell you when the battery needed charging by having the PIC monitor the supply line voltage.:)

spec

2016_09_17_Iss1_ETP_LED_low_current.png
 
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be80be

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The high brite leds the only way to go and spec
constant current generator so that the LEDs would remain at constant brightness with changes in battery voltage.
good idea
 
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