Require help with LEDs and some PCB design

Thread Starter

William A Rose

Joined Feb 5, 2022
45
You may not be completely happy with the final appearance of this LED design. If you really want to put this much effort into such a project, you should start with a bit of lighting design/effect "research".

First, some modern LEDs are extremely bright and become blinding at 20mA as @Yaakov suggests so you should connect a small group and test them at currents down to 1 to 5 mA range (less blinding). At 1mA , your power supply can be a very manageable 2 amps instead of 40 amps as yaakov feared.

next, you should build a small section of a stripe. You may (likely?) find that your rows of rows design does not suffficently distribute night. LEDs are point sources and intense. They will not look like a red stripe. You may have much better effect by distributing your red LEDs in the whole area of the red stripe. Looking at your design without the red or blue infill will give a better approximation of the final result. Finally, you may want to look into light diffusing films or resins. You can fire the LEDs sideways into a light diffusing resin (hot glue or casting polymer with some TiO2 blended in.
View attachment 259974
I have both a colorized version and a black and white version of this for the very reason you stated. I don't remember posting the pic above, but I have that, too. Haha.
 

Thread Starter

William A Rose

Joined Feb 5, 2022
45
Which one? I like Eagle. It was the third I tried and I decided it was sufficient and stopped looking. Others like KiCad.

Well, I thought I had three. Design Spark, Easy EDA, and Eagle. The latest one is by Advanced Circuits and is called PCB Artist. It was a free download and supposed to be packed with features. I haven't used it yet. Just been reading the tutorial. That is pretty good. Of course, I have NO experience with such software, so this should be fun once I get past the learning curve. I'm sure to make a mess. A real Rat's Nest. Hehehe.

The 555 timer symbol in Eagle was goofy, so I made my own.
Believe us when we say your flag project would be easier using a microcontroller.

I was in that camp for a long time. I preferred to design with logic chips. When I retired, I wanted to build some LED cubes and scrolling LED signs. Once I started down that path, microcontrollers were the only feasible solution. I missed the Raspberry Pi revolution, so I decided to use a new platform called C.H.I.P. that was a Kickstarter project. It's main claim to fame was that for $9 (plus a keyboard, monitor, and mouse), you had a working Linux computer. Then they went out of business due to poor management and I migrated my code to Raspberry Pi. A similarly configured Pi Zero W would cost more than twice that, have fewer I/O's, and no ADC.

I recently programmed an EPROM with a 4 digit binary to BCD converter. I used C to create the data to program and was fairly certain I programmed it correctly, but I needed to be certain. I contemplated using some counters to test it. But that would have required me to implement a BCD to binary converter or do something silly like watch the display while incrementing a counter. So I wrote a program to do it with an Arduino Mega. That lead to writing half a dozen programs for Uno to test DRAMs and check 5-6 dozen programmed PROMs I picked up in a big lot of components on eBay a decade or two ago to see if any of them could be repurposed.
 

ElectricSpidey

Joined Dec 2, 2017
2,757
As to the flashing/pulsing of the LEDs, what I have envisioned is having two feed wires going to each LED. The constantly-on portion is easy. Simply a hot and ground to each LED. I'll put in a Zener Diode in each feed so that the voltage in each feed does not go to the other feed. The constantly-on ill have a common resistor after the LEDs. The pulsing feed will come from the cascaded 4017s. Those feeds will have both a Zener Diode and a resistor and connect to the positive terminal on the LED. I do not know a better way. Again, I do not wish to mess with a microcontroller. Maybe someday, but not now.
I already worked that out for you in post #28, but if you think diodes can do a better job than load drivers...knock yourself out.

Cascaded 4017s will not give you the random effect you are looking for.
 

MisterBill2

Joined Jan 23, 2018
18,167
Referencing post #40, the reason that additional gates are included in the multiple counter circuits is that the CD4017 is a RING COUNTER. This means that for all count values one output is active. The 4017 counts from zero through 9 and then rolls back to zero and keeps counting, if the clock is enabled. So there is no way to inhibit at least one output.
Also, that circuit is not a series circuit, it only illuminates one LED at a time. Hence none of those LEDs can be part of the static display. This means that the circuit board is going to have a whole lot of components.

I have the Eagle PCB program and while it is good, I find a very large learning curve because it is totally different from AutoCad, which I have used since version 10. There is no similarity between them of any of the commands. So it is a challenge.
 

dl324

Joined Mar 30, 2015
16,839
Just noticed I had a wiring mistake in the schematic I posted. Here's the correction:
1644336757505.png
Also updated the original post.

Well, I thought I had three. Design Spark, Easy EDA, and Eagle. The latest one is by Advanced Circuits and is called PCB Artist. It was a free download and supposed to be packed with features. I haven't used it yet. Just been reading the tutorial. That is pretty good. Of course, I have NO experience with such software, so this should be fun once I get past the learning curve. I'm sure to make a mess. A real Rat's Nest. Hehehe.
Just pick one and see if it satisfies you needs. Some say Eagle is too difficult to learn, but I didn't find that to be the case.
 
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Thread Starter

William A Rose

Joined Feb 5, 2022
45
I already worked that out for you in post #28, but if you think diodes can do a better job than load drivers...knock yourself out.

Cascaded 4017s will not give you the random effect you are looking for.
Once I get a representation of my circuits, I'll post a pic. I'll look at your post again as soon as I can. Please keep in mind, I am a novice novice. I don't necessarily know what can and can't be done. I only know what comes to mind. I'll build my circuits on a breadboard and try them out as I get to it. I still have to do the math and buy some components. I am slow at this. Painfully slow. Heart problems keep me down.
 

Ya’akov

Joined Jan 27, 2019
9,069
I always wanted to build something with my own addressable LEDs using Dallas Semi 1-Wire addressable switches. They have a variety, like this one that seem like you could do some pretty neat, lightweight stuff.

Since every device is has a unique address, you could add, remove, replace panels arbitrarily. Also, you could have very little active circuitry close to the LEDs, and centralize all the logic. Maybe some time I'll do something like it.

Unfortunately, the TS' aversion to MCUs (which is entirely his right to have, it's his project and so far as I can tell he is also the customer) means that stuff like this is a non-starter.
 

ElectricSpidey

Joined Dec 2, 2017
2,757
Once I get a representation of my circuits, I'll post a pic. I'll look at your post again as soon as I can. Please keep in mind, I am a novice novice. I don't necessarily know what can and can't be done. I only know what comes to mind. I'll build my circuits on a breadboard and try them out as I get to it. I still have to do the math and buy some components. I am slow at this. Painfully slow. Heart problems keep me down.
Yes, I would very much like to see your idea in schematic form.

And don't mind my gruff remarks...that's just me.
 

Thread Starter

William A Rose

Joined Feb 5, 2022
45
This might upset some folks. Sorry. I liked it.

1644350213758.png

And this:

1644350322654.png

This is just missing the diodes in the Timer circuit. Are they really necessary? And that AND gate in the cascaded 4017 circuit.....is it necessary? Why?

Thanks for any and all replies.
 

MrSalts

Joined Apr 2, 2020
2,767
This might upset some folks. Sorry. I liked it.



And this:



This is just missing the diodes in the Timer circuit. Are they really necessary? And that AND gate in the cascaded 4017 circuit.....is it necessary? Why?

Thanks for any and all replies.
I love it! Your concentration is amazing. You might want to look up a very easy to use circuit builder called Fritzing. Your mind / visualization seems to work in the mode that Fritzing uses to represent a circuit. It will be much faster for you than your line drawings (if I remember correctly). It's been a while since I used it with some students.
https://fritzing.org/learning/tutorials/building-circuit
The image below looks like the tram map in a German city.
C1E91D42-A054-43B7-9372-508A98C787DB.jpeg
 

ElectricSpidey

Joined Dec 2, 2017
2,757
You can't drive LEDs like that with a single resistor because the outputs from a 4017 are push pull, well not @ 12 volts anyway.

The only saving grace is a 4017 probably couldn't produce enough current to destroy that many LEDs.

I don't see your method of producing the pulses in that image, that's what I wanted to see.
 
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dl324

Joined Mar 30, 2015
16,839
And that AND gate in the cascaded 4017 circuit.....is it necessary? Why?
I'm assuming they implemented the cascading circuit shown in the TI/Harris datasheet:
1644352677673.png
The AND gates are required so only one counter increments on the rising edge of the clock.

While you can load the outputs of the counters without affecting the count function, it's not a good design practice. Whether you can get the current the circuit is designed for is another matter.
1644352872987.png
 

Thread Starter

William A Rose

Joined Feb 5, 2022
45
I love it! Your concentration is amazing. You might want to look up a very easy to use circuit builder called Fritzing. Your mind / visualization seems to work in the mode that Fritzing uses to represent a circuit. It will be much faster for you than your line drawings (if I remember correctly). It's been a while since I used it with some students.
https://fritzing.org/learning/tutorials/building-circuit
The image below looks like the tram map in a German city.
View attachment 260143
Hehe. I lived in Bremerhaven, Germany for several years.

That pic is a screen capture from a YouTube video, but is very similar, I suppose, to what I am drawing up using CorelDraw. I have downloaded three different PCB programs. Design Spark, Easy EDA, Eagle. Just ran across one called PCB Artist by Advanced Circuits. I haven't really used any of them yet. I am reading the tutorial for the latest software. It looks to be easy enough. We'll see. I do plan to create proper schematics and whatever else goes along with all this.

Before I attempt to create a PCB layout, I have to figure out how to import the shape and size of the board as I have designed it in the graphics program. All in good time, I suppose.

I will look at the program you recommended.
 

Thread Starter

William A Rose

Joined Feb 5, 2022
45
You can't drive LEDs like that with a single resistor because the outputs from a 4017 are push pull, well not @ 12 volts anyway.

The only saving grace is a 4017 probably couldn't produce enough current to destroy that many LEDs.

I don't see your method of producing the pulses in that image, that's what I wanted to see.
As soon as I get it drawn up, I'll post it. I don't know what you mean by push/pull. The single resistor will be for the always-on circuit. That's what I envision, anyway. I don't know precisely what I am doing. I am learning as I go.
 

Thread Starter

William A Rose

Joined Feb 5, 2022
45
I'm assuming they implemented the cascading circuit shown in the TI/Harris datasheet:
View attachment 260145
The AND gates are required so only one counter increments on the rising edge of the clock.

While you can load the outputs of the counters without affecting the count function, it's not a good design practice. Whether you can get the current the circuit is designed for is another matter.
View attachment 260146
Hmmm. That's the first I have looked at the innards of the 4017. Cool!
 

Thread Starter

William A Rose

Joined Feb 5, 2022
45
If you want to produce PWM with a 555 you want to adjust the duty cycle not the frequency.

Push/pull means the outputs go to both rails.
Found this:
Pulse-width Modulation
Pulse-width Modulation
Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load. Along with maximum power point tracking (MPPT), it is one of the primary methods of reducing the output of solar panels to that which can be utilized by a battery. PWM is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching, because their inertia causes them to react slowly. The PWM switching frequency has to be high enough not to affect the load, which is to say that the resultant waveform perceived by the load must be as smooth as possible.

I still don't understand all of that. I'll have to think on it. Why would an LED care about any PWM?

And this:
Duty Cycle
Duty Cycle
A duty cycle or power cycle is the fraction of one period in which a signal or system is active. Duty cycle is commonly expressed as a percentage or a ratio. A period is the time it takes for a signal to complete an on-and-off cycle. As a formula, a duty cycle (%) may be expressed as: D=PW/T×100% Equally, a duty cycle (ratio) may be expressed as: D=PW/T where D is the duty cycle, PW is the pulse width (pulse active time), and T is the total period of the signal.

Ha. Ok. Learned something.

Push/Pull outputs to rails? Do you mean positive and ground?
 
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