NODEMCU Controlled PWM 3W 700mA LED Circuit - Would like feedback on Open Source project...

Thread Starter

Mister Nerdeus

Joined May 31, 2018
4
After doing some research, the enclosed circuit designs are what I came up with. I am redesigning the circuit diagrams using Eagle and plan to open up these up to the Open Source community so I would welcome any feedback from much more knowledgeable people if this is a sufficient design or if there is something better that I should consider.

GOALS

· Use common, easily available parts (besides circuit board).
· Use separate 24VDC regulated 240W (10A) power supply to drive each “LED Grow Bar”.
· Each “LED Grow Bar” consists of a total of (80) 3W 700mA LEDs (240W max).
· Each “LED Grow Bar” consists of (7) PWM channels to control (7) different types of LEDs.
· A NodeMCU-ESP8266-12E microcontroller along with ULN2003A ICs will be used to control the PWM.
· PWM output to be 3.3VDC using standard RJ45 connectors. These can be linked together as many as needed (what would be the max number?).
· Power Supply Plug would be a 10A standard C13/C14 computer power cord rewired to have 24VDC; 3.3VDC and GROUND.
· Plugs to LEDs would be common 10pin PC board Header connection plugs.

I included three circuit layouts. The PWM generator; the LED drivers; the LED layout.
LED PWM Driver V.1.00.png LED Series Layout V1.00.png NodeMCU-ESP8266-12E.jpg
Thank you for your time and feedback!
 

Hymie

Joined Mar 30, 2018
708
After doing some research, the enclosed circuit designs are what I came up with. I am redesigning the circuit diagrams using Eagle and plan to open up these up to the Open Source community so I would welcome any feedback from much more knowledgeable people if this is a sufficient design or if there is something better that I should consider.

GOALS

· Use common, easily available parts (besides circuit board).
· Use separate 24VDC regulated 240W (10A) power supply to drive each “LED Grow Bar”.
· Each “LED Grow Bar” consists of a total of (80) 3W 700mA LEDs (240W max).
· Each “LED Grow Bar” consists of (7) PWM channels to control (7) different types of LEDs.
· A NodeMCU-ESP8266-12E microcontroller along with ULN2003A ICs will be used to control the PWM.
· PWM output to be 3.3VDC using standard RJ45 connectors. These can be linked together as many as needed (what would be the max number?).
· Power Supply Plug would be a 10A standard C13/C14 computer power cord rewired to have 24VDC; 3.3VDC and GROUND.
· Plugs to LEDs would be common 10pin PC board Header connection plugs.

I included three circuit layouts. The PWM generator; the LED drivers; the LED layout.
View attachment 153455 View attachment 153456 View attachment 153457
Thank you for your time and feedback!
Your proposal includes the use of a standard IEC 60320 appliance coupler (C13/C14), but rather than connecting to Live/Neutral/Earth, it is used to connect 24Vdc and 3.3Vdc.

I would strongly advise against this since someone could inadvertently connect the mains supply to your low voltage circuits. You should investigate the use of an alternative connector, not of the type normally used for mains connections.
 

Thread Starter

Mister Nerdeus

Joined May 31, 2018
4
Your proposal includes the use of a standard IEC 60320 appliance coupler (C13/C14), but rather than connecting to Live/Neutral/Earth, it is used to connect 24Vdc and 3.3Vdc.

I would strongly advise against this since someone could inadvertently connect the mains supply to your low voltage circuits. You should investigate the use of an alternative connector, not of the type normally used for mains connections.
Thank you for your response! Do you know of any such alternative connector that is readily available that can handle the current load? I am assuming that particular topic is better suited for the “Power Electronics” forum in which case, I shall pose that forum that particular concern. My cost benefit & risk assessment based upon the requirements and “risks”, that one included, still led to that use case. I would like to use an alternative that is cost effective – just for the safety factor. So far, I have no better alternative which is why I am on these forums.

Again, thank you!
 

ElectricSpidey

Joined Dec 2, 2017
690
The only advice I can give is...be sure to watch your wattage ratings on those Darlington drivers, it's true that each channel can handle 500mAs but not all 7 at the same time.
 

Thread Starter

Mister Nerdeus

Joined May 31, 2018
4
The only advice I can give is...be sure to watch your wattage ratings on those Darlington drivers, it's true that each channel can handle 500mAs but not all 7 at the same time.
Thank you for your response! I know I am pushing the current requirements here. At first, I was going for a logic level MOSFET circuit for each channel – then I saw the above concept of using ICs and the “elegant” design. I thought to use IC dip sockets to swap out if any of the ICs burnt out over time.

This particular parallel setup would allow for 2.1A of current per ULN2003A at any given time – 3 outputs per IC. Does anyone know for sure if this is too much current draw on each IC?

I am not bound by this design so I can make any recommended changes. So if anyone reading this has a better solution I should check into, please feel free to educate me on the subject. It has been many years since I have had the pleasure of delving into the electronics realm directly. I am a software guy by trade so I will have no “hurt” feelings for being called out on design principles from those who actually know and most likely done these things.

Again, to any and all – thank you for your input and time!
 

ElectricSpidey

Joined Dec 2, 2017
690
Using raw wattage calculations I would say you are probably pushing the limits of the driver chips.

Without actual tests to determine what kind of voltage drops you will get across the Darlington CE junctions it is hard to say.

I suggest you get some chips and place dummy loads on them and see what happens, you will need the PWM setup as well, as this complicates things a bit, as far as wattage.

Bottom line is…test…test…test.
 

dendad

Joined Feb 20, 2016
3,006
You will need to reverse the LEDs and have their Anodes common and from +24V, not 0V.
The drivers do not source current, only sink it, so they switch to 0V when on.
And yes, DO NOT USE MAINS CONNECTORS FOR DC!!!
I have seen it done, using an expensive external speaker for a movie projector wired to a mains plug so a standard extension lead could be used. Sounds very handy, and the result in this case was a "helper" plugged the speaker into a 240mains socket. I wish I actually saw in, and not just the result. I bet they jumped ;)
Those connectors used for solar panels may well be worth a look.
 

Hymie

Joined Mar 30, 2018
708
Thank you for your response! Do you know of any such alternative connector that is readily available that can handle the current load? I am assuming that particular topic is better suited for the “Power Electronics” forum in which case, I shall pose that forum that particular concern. My cost benefit & risk assessment based upon the requirements and “risks”, that one included, still led to that use case. I would like to use an alternative that is cost effective – just for the safety factor. So far, I have no better alternative which is why I am on these forums.

Again, thank you!
You could consider GX20 aviation connectors – available rated to 10A.
 

Thread Starter

Mister Nerdeus

Joined May 31, 2018
4
Thanks to all that have responded with feedback! I have updated the design based upon feedback. The power connector issue because of the common 24VDC on the LEDs (for each Light Bar this is to create) I am currently rethinking. Maybe something that can just “slide” in from the top for easy Light Bar install/removal/maintenance. But that issue is outside the topic of this forum.

Any feedback on these updated designs would be welcome and greatly appreciated!NodeMCU-ESP8266-12E.jpg PWM2.jpg LED-Layout.jpg
 
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