Raising 4017 output to 11V

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
Hi all. First off, I do not have a schematic handy. I have a circuit with 6v DC powering a 555 and 4017. I have purchased some 10w leds. They are tri colour RGB. Red has an operating voltage of 6v. Blue and Green both need 11v. LED Specs are:
Red 120-150 lumens, Green 200-300 lumens, Blue 70-100 lumens
- Vf: Red 6-8V, Green 9-12V, Blue 9-12V
- Emitting angle: 140 degrees
- Working current: 300mA max per colour

My question is what is the best way to increase the output (signal) of the 4017 to drive these LEDs? Please don't immediately flame me for not putting up a schematic. I am not asking for the specifics of the circuit I need - just the best approach. Should I be thinking mosfets, transistors, optocouplers, transformers or something totally different?

Cheers
:)
 

MrChips

Joined Oct 2, 2009
21,325
Increase the supply voltage to 12V.
And then increase the value of the LED series resistor to suit the desired brightness.
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
My primary supply voltage is 12V. Then I step it down to 6v using a Polulu 6v 1a shifting regulator for the 555 and 4017. So I can tap into the 12v supply for the leds...just not sure how to interface with the signal voltage coming from the 4017. I am thinking I may have to use a relay?
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
Crikey Mr Chips!! I can't believe I didn't think of that! *hides head in shame*. I can't test it now as I am at work …. just one question. How much voltage drop does the 4017 have (ie will 12v supply mean 12v signal) and what current can it drive? ( And I guarantee..whatever it may seem...that was not two questions..)

:)
 

panic mode

Joined Oct 10, 2011
1,837
if the LEDs are 10W, and have forward drop of some 6V...11V, then they must draw significant current. that is much much more than 4017 outputs can supply.

here is an example of using transistors to increase load current:
https://www.eleccircuit.com/wp-content/uploads/2017/06/siren-light-from-running-light.jpg
just replace lads with LED + resister circuits.
when active, transistors in such configuration will have very low drop (0.1V or so)
 
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Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
Thanks Panic Mode... btw ..

"There are 10 types of people in the world: those who a) understand binary, b) those who don't and c) those who understand any numbering system." --> Wouldn't that be 11 types?
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
Hmm it was the current draw on the 4017 that originally got me on this path....but then looking at the specs it says max 300Ma per colour … but you are right Panic Mode.... 300Ma at 6 ( or 11 ) volts does not equal ( or even come close to ) 10W. I am wondering if the 10W is the TOTAL power when all colours are at maximum operating voltage (works out at 9.6 by my calculation). ??? In which case I'd only be looking at 300Ma draw on the 4017 at any one time.
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
Thanks for the schematic Panic Mode! I will try that circuit. If I replace the two 6v lamps with one 12 v led and then for the 6v led put the right value resistor in line...that should work? Sorry about the noob questions but I am pretty amateur (if you hadn't picked up on that already) with electronics.

Thanks all for the help and comments and I'll let you know either way how it works out.

:)
 

eetech00

Joined Jun 8, 2013
1,937
Thanks for the schematic Panic Mode! I will try that circuit. If I replace the two 6v lamps with one 12 v led and then for the 6v led put the right value resistor in line...that should work? Sorry about the noob questions but I am pretty amateur (if you hadn't picked up on that already) with electronics.

Thanks all for the help and comments and I'll let you know either way how it works out.

:)
Hi

The circuit would be better if you used mosfet transistors. They are voltage driven and don't require drive current from the 4017 outputs like BJT transistors do.

eT
 

ElectricSpidey

Joined Dec 2, 2017
1,175
I’m surprised no one has mentioned that there is little overhead for limiting LEDs that need 11 volts with a resistor when only 12 volts is available.

Be damn sure to keep those things cool, in fact I wouldn’t run them over 100 mA.
 

Audioguru again

Joined Oct 21, 2019
1,577
The CD4017 will produce smoke when it tries to drive the 220 ohm series transistor base resistors and is powered from 12V. Powered from 6V the output current from the CD4017 is too low to drive the transistor base.
Like eetech00 said, use Mosfets instead of transistors.
 

panic mode

Joined Oct 10, 2011
1,837
"There are 10 types of people in the world...
that is because "10" could be just about any number - depending on chosen base.
it is two in binary (base2)
it is eight in octal (base8)
it is ten in decimal (base10)
it is sixteen in hexadecimal (base16)

it could be 3, 11, 21, 237 or whatever your base is.
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
that is because "10" could be just about any number - depending on chosen base.
it is two in binary (base2)
it is eight in octal (base8)
it is ten in decimal (base10)
it is sixteen in hexadecimal (base16)

it could be 3, 11, 21, 237 or whatever your base is.
Good point!
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
I’m surprised no one has mentioned that there is little overhead for limiting LEDs that need 11 volts with a resistor when only 12 volts is available.

Be damn sure to keep those things cool, in fact I wouldn’t run them over 100 mA.
I had already thought I was cutting it fine. They have a 9-12V range so I might have to reduce brightness and cut back a volt or two.

Sounds like mosfets are the way to go!

Cheers all.
:)
 

Thread Starter

Blue Wolf

Joined Jun 20, 2019
17
Thanks all for your input on this one. N-Channel mosfets were the way to go..all up and running (on prototype board anyway lol) now!
 
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