Where has this forum been all my life?

Long story short, I was HEAVILY into digital electronics from 1979 to the late 80s. Unfortunately, life took over, so I have forgotten many things. plus, I'm old now.

I built prototype of a 3-channel LED chaser with some diodes and transistors. It worked perfectly. Ten I used EasyEDA to design a board. 8 revisions, verified a zillion times and it just didn't work.

Basically, it uses 3 strings of 10 LEDs each, paid out like 1A 1B, 1C, 2A, 2B, 2C, etc. Gives a really cool effects when it runs. Well, WHEN it runs.

So I want to be able to control the speed with a 555 and use a simple counter to count to 3, triggering each channel, then reset and repeat.

That's where I get stuck. I can't for the life of me remember which 74 series TTL chip to use as a counter. I looked through a whole bunch and their data sheets, and my 58 year old brain cells can't remember the simplest thing.

I thought maybe an '148, then I looked at the '390. Then I can't remember if the 3rd "count" would be able to drive 10 LED's then reset the counter.

Or, do I need to use the 4th count to do the reset, but then will there be a noticeable delay in the 'visual'. Getting old is not cool.

So, I'll use the 555 as a timer, whatever chip hopefully someone can recommend, and possibly a one of the low-end TTL, if I need an inverter or something to kick off the LEDs

I hope I explained this well enough.

Thanks for ANYONE who can help this old guy bring back his love of digital!

Mike

 

First, since the 80s, TTL has become obsolete. TTL chips will be scarce or unavailable. CMOS technology logic chips is the current technology.

For your application, I’d recommend a CD4017 (or it’s equivalent such as a CD74HCT4017). It’s a decade counter, meaning it has 10 outputs which are sequentially activated (one by one) with each clock pulse.

Use your 555 circuit to provide the clock signal. Tie your 3 LED channels to outputs 0, 1 and 2. Route output 3 to the 4017’s Reset pin. There will be no significant delay, since as soon as pin 3 goes high, the counter will reset to 0. That is, on the 4th count, it will reset to 0. There will be no perceptible delay.

An important difference between TTL and CMOS technology is that ALL inputs must be connected. Unused pins must be tied high or low, with a resistor, as appropriate. The resistor can be between 3k and 4k.

You will need a BJT or MOSFET transistor to drive the LED channels.

 

First, since the 80s, TTL has become obsolete. TTL chips will be scarce or unavailable. CMOS technology logic chips is the current technology.

For your application, I’d recommend a CD4017 (or it’s equivalent such as a CD74HCT4017). It’s a decade counter, meaning it has 10 outputs which are sequentially activated (one by one) with each clock pulse.

Use your 555 circuit to provide the clock signal. Tie your 3 LED channels to outputs 0, 1 and 2. Route output 3 to the 4017’s Reset pin. There will be no significant delay, since as soon as pin 3 goes high, the counter will reset to 0. That is, on the 4th count, it will reset to 0. There will be no perceptible delay.

An important difference between TTL and CMOS technology is that ALL inputs must be connected. Unused pins must be tied high or low, with a resistor, as appropriate. The resistor can be between 3k and 4k.

You will need a BJT or MOSFET transistor to drive the LED channels.

Thank you for the great info! Very sad to hear about TTL.

I did forget to mention one thing... I need these to run off of coin cells - I will have to put a couple in series and then some in parallel to make that 5V.

Thanks again!

Mike

 

Thank you for the great info! Very sad to hear about TTL.

I did forget to mention one thing... I need these to run off of coin cells - I will have to put a couple in series and then some in parallel to make that 5V.

Thanks again!

Mike

If you are trying to use coin cells, be glad that you will be using CMOS instead of TTL, which were relative power hogs.

How long do you want this thing to operate off of a set of batteries?

Have you done a power budget at all -- even just for the LEDs you plan to use?

 

A Coin-Cell will be "maxed-out" with just 2 or 3 LEDs.
They will not provide enough Current for your project.
.
.
.

 

If you are trying to use coin cells, be glad that you will be using CMOS instead of TTL, which were relative power hogs.

How long do you want this thing to operate off of a set of batteries?

Have you done a power budget at all -- even just for the LEDs you plan to use?

Thank you for the reply. When I originally prototyped it, i was only using resistors, transistors and diodes. I used 4 CR2477 lithium batteries and got about 18-19 hours out of it. Only needed it to work for about 8-10 for an event.

How many LED's? 30. Yes, 30. 20ma 2V. 3 strings of 10 each.

Now that I will go CMOS (thanks for the TTL/CMOS power tip, it's been a long time.)

I guess I am just "nostalgic" about TTL. I "grew up" on it.

Thanks
Mike

 

A Coin-Cell will be "maxed-out" with just 2 or 3 LEDs.
They will not provide enough Current for your project.
.
.
.

Thanks for the reply. I've done a lot with LED's and coin cells. I make backstage passes for various events and over the decades have made all kinds of various things. They only need to run for a day. And like you said 2-3 LEDs usually last about 20-24 hours, obviously depending upon all their specs.

This project will have 10 on at a time. If you check the previous reply, I got much more time out of it than I will need for the event.

And I use battery holders, so if they want to "continue the fun", they can just change out the batteries.

I will also have a small slide switch on it so they can turn it off if they want.

Thanks

Mike

 

I too played digital from '78, just gradually went to micros then microcontrollers - still there at ~70.
I'd use a shift register with parallel load. A short delay at power up to load pattern then last output feeds serial input.
A 74x95 or 194 look possible, don't know current family types. G.H <<<)))

 

Welcome to AAC!

How many LED's? 30. Yes, 30. 20ma 2V. 3 strings of 10 each.

Unless this will be used in bright ambient lighting, you could probably use ultrabright LEDs operating at a much lower current.

1. Is each LED in a string of 10 turned on sequentially with only one on at a time?
2. What is the relationship between the strings? One active at a time, all active at the same time?
3. What is the area/volume available for the circuit?
4. How much area/volume is taken up by the batteries?

my 58 year old brain cells can't remember the simplest thing

I've got a decade on you and I can still recall the functionality of many TTL parts from memory

 

I too played digital from '78, just gradually went to micros then microcontrollers - still there at ~70.
I'd use a shift register with parallel load. A short delay at power up to load pattern then last output feeds serial input.
A 74x95 or 194 look possible, don't know current family types. G.H <<<)))

Thanks for the reply. I ended going with the CD4017B and NE555N and pretty much finalized the circuit 3 days ago. I am doing a run test with two CD2032's. I started it at 10:00 pm Thursday 8/18/22 and it is STILL running. Dimming a bit, but I just want to see how long it will last even tho the "peak" period is over.

That's awesome you're still into it at 70. I am 58 as mentioned, but will never not love digital stuff. I have been doing a lot with Arduinos as well. Working on a device to do something I've never seen before for a small business I wanted to start.

Mike

 

Welcome to AAC!

Unless this will be used in bright ambient lighting, you could probably use ultrabright LEDs operating at a much lower current.

1. Is each LED in a string of 10 turned on sequentially with only one on at a time?
2. What is the relationship between the strings? One active at a time, all active at the same time?
3. What is the area/volume available for the circuit?
4. How much area/volume is taken up by the batteries?

I've got a decade on you and I can still recall the functionality of many TTL parts from memory

I think I remember more than I give myself credit for.

All good questions you asked!

1. Is each LED in a string of 10 turned on sequentially with only one on at a time?

The full string of 10 is on for that cycle.

1. What is the relationship between the strings? One active at a time, all active at the same time?

One string at a time for the count of 3. They alternate. LED 1, LED 11, LED 21, LED 2, LED 12, LED 22, etc.

1. What is the area/volume available for the circuit?

Area of entire circuit including the LEDs is 3.5" x 5.5" (Approx. 19.25 sq. in.)

1. How much area/volume is taken up by the batteries?

2 CR2032 batteries in BA2032SM holders 5/8" x 1-1/8" (Approx. 1.4 sq. in.)

 

All good questions you asked!

Since you already finished your design, you didn't really need to respond. But, thanks anyway.

You mentioned you were into Arduinos. I had always wanted to work on scrolling LED displays and LED cubes, but didn't have time until I retired. They were among the first projects I did when I started getting into microcontrollers. I chose to use Linux based single board computers because they had more resources and interruptions by the OS aren't important or noticeable.

I missed the Raspberry Pi revolution, so I opted to go with a new one called C.H.I.P.. (advertised as a $9 computer). The Company (NTC) went under, so I have about a dozen little boat anchors and switched to Pi Zero W.

 

Since you already finished your design, you didn't really need to respond. But, thanks anyway.

You mentioned you were into Arduinos. I had always wanted to work on scrolling LED displays and LED cubes, but didn't have time until I retired. They were among the first projects I did when I started getting into microcontrollers. I chose to use Linux based single board computers because they had more resources and interruptions by the OS aren't important or noticeable.

I missed the Raspberry Pi revolution, so I opted to go with a new one called C.H.I.P.. (advertised as a $9 computer). The Company (NTC) went under, so I have about a dozen little boat anchors and switched to Pi Zero W.

That's cool. LOVE Linux, but just didn't get fully into it unfortunately. I don't know why since I worked at Bell Labs in NJ in the late 80, where , as you know UNIX was created. I also was leaning C at the time and met Kernighan and Ritchie - their lab was right down the hall from ours. AWSOME GUYS. They said anytime you have a question, come by. How awesome to be taught C by the guys wrote wrote it! They both signed their book for me. Good times.

I was pretty heavily invested in Arduino stuff (TONS of shields, etc.) before the Pi was even baked. (Sorry.)

Ah yes the scrolling LED display... One of the first BASIC programs I worked on my little Apple ][+ back in the 80s. Also have one of those persistence of vision wands that as you shake it from side to side, the display appears to scroll in midair. Still have it, too.

 

met Kernighan and Ritchie

That's neat. C and awk are still two of my favorites.

I was on the other coast around that time and got to meet Hewlett, Packard, Noyce, Grove, and Moore. I was in the Homebrew Computer Club when Jobs was in it, but our paths never crossed.

 

That's neat. C and awk are still two of my favorites.

I was on the other coast around that time and got to meet Hewlett, Packard, Noyce, Grove, and Moore. I was in the Homebrew Computer Club when Jobs was in it, but our paths never crossed.

That is SO awesome! Oh to have been old enough at the time of the Homebrew Computer Club. So jealous!

So now I have a question... I have those 30 2V 20ma LED's. I didn't want them at full brightness due to the application. But I do want them brighter. I lowered the resistor value and nothing changed. Then I removed the resistors and nothing changed.

Then I noticed that the output is only 10ma... So I googled around to find out what I could do to kick that up to at least 20 ma...

Do you know a good little transistor or something I could use to kick that up to 20ma? I can alwasy add some resistance if it's too bright.

thanks

Mike

 

So now I have a question... I have those 30 2V 20ma LED's. I didn't want them at full brightness due to the application. But I do want them brighter. I lowered the resistor value and nothing changed. Then I removed the resistors and nothing changed.

LED current is being limited by what the counter outputs can source.

Do you know a good little transistor or something I could use to kick that up to 20ma? I can alwasy add some resistance if it's too bright.

Any general purpose NPN transistor could do it as could 2N7000. Are you using standard brightness LEDs? Ultra-bright LEDs would give more light at a lower current.

If you want to reduce the amount of wiring you'd need, you could use ULN2003, ULN2803, TBX62003, TBX62083, etc.

EDIT: I'm assuming you would drive the LEDs low side. If you want to continue to drive the LEDs high side, you'll need another inverter stage.

 

LED current is being limited by what the counter outputs can source.
Any general purpose NPN transistor could do it as could 2N7000. Are you using standard brightness LEDs? Ultra-bright LEDs would give more light at a lower current.

If you want to reduce the amount of wiring you'd need, you could use ULN2003, ULN2803, TBX62003, TBX62083, etc.

Thanks for that great tip. I happen to have a load of BC547B's from a previous project.

The LEDs I'm using are from Amazon: https://www.amazon.com/gp/product/B01BUVHSQQ

They are standard brightness and I like the yellow color they give off and the fact they have a flat top.

I never thought that higher brightness LEDs would use less current.

S if I get some of the 2N7000's you mentioned that would work for these standard brightness LEDs?

If they made a 5mm flat top with this yellow in a higher brightness, I'd love to find it. I'll google around...

Thanks!

Mike

 

The LEDs I'm using are from Amazon: https://www.amazon.com/gp/product/B01BUVHSQQ

They are standard brightness and I like the yellow color they give off and the fact they have a flat top.

They're called super bright, which is the same as ultra-brights. Standard brightness would be in the few to few dozen mcd range.

A disadvantage of clear/non-diffused enclosures is that the viewing angle is much smaller.

I never thought that higher brightness LEDs would use less current.

Brightness is typically specified at 20mA, so an ultra-bright would give more light than a standard brightness LED at a lower current.

if I get some of the 2N7000's you mentioned that would work for these standard brightness LEDs?

There's no advantage to using 2N7000 instead of the BC547 you already have. When you operate them as switches, you need to provide a base current that's 5% of the desired collector current. 2N7000 are easily damaged. I've damaged several in the past few years and I was trying to handle them properly. They didn't die outright; they just exhibited higher than normal leakage current.

 

They're called super bright, which is the same as ultra-brights. Standard brightness would be in the few to few dozen mcd range.

A disadvantage of clear/non-diffused enclosures is that the viewing angle is much smaller.
Brightness is typically specified at 20mA, so an ultra-bright would give more light than a standard brightness LED at a lower current.
There's no advantage to using 2N7000 instead of the BC547 you already have. When you operate them as switches, you need to provide a base current that's 5% of the desired collector current. 2N7000 are easily damaged. I've damaged several in the past few years and I was trying to handle them properly. They didn't die outright; they just exhibited higher than normal leakage current.

Thank you for that great info - sorry my lack of knowledge (or recollection,) has decreased so much over the years. I will stick with the 547's. I will have to figure out the 5% that you mentioned. I never like to ask for the answer. I have a couple hundred of those transistors, so I don't mind destroying some to figure it out. If I just can't figure it out, then maybe I'll ask, but I'll list what tried.

For my application, the viewing angle is more than sufficient.

Kinda funny in a way, how someone who worked for the place that invented the transistor doesn't remember much about them!

 

I will stick with the 547's. I will have to figure out the 5% that you mentioned.

Note that the 5% guideline for BC547 doesn't apply to all transistors. General purpose 2N transistors use 10%. The appropriate number can be found in the datasheet.

Kinda funny in a way, how someone who worked for the place that invented the transistor doesn't remember much about them!

Completely understandable that you wouldn't have expertise in everything your employer did.

When I worked at HP Labs, we reported to Bill Hewlett. I doubt that he had detailed knowledge of everything the labs worked on.