LED circuit for 1/6 scale diorama

JDGafford said:

When I connect 13 to 16, it shuts down the circuit.
Using your original diagram you gave me, and putting pin 13 to ground, here is what I get....

LED #1 comes on....stays on for 1.4 seconds and turns off.
LED #2 comes on .7 seconds after LED #1 turns off and stays on for 1.4 seconds.
LED #3 comes on immediately after LED #2 turns off, flashes twice and turns off.
Then the circuit resets.

So, is it possible to have #1 and #2 to turn on and stay on throughout the duration of the circuit?

And, is there a way to have LED #3 to turn on 1.4 seconds after LED #2 comes on and blink 6+ times before turning off and resetting the circuit?

Also, I can't use 3 inputs on the first and second bank of LED's.
If I use 2, it will illuminate, but it's dim.
If I use 3, it wont illuminate at all.
Im using only 1, 3 volt white light LED with no resistor.
using 2 LED's dims them both unless i bump up the input voltage to 6 volts.

Thank you again for all your help.

Click to expand...

Ok, try this... but, when rediculous speed comes on, the light speed sign will dim a bit.

When the ludicrous speed sign comes on, the rediculous sign will dim a bit (but the light speed sign will NOT dim more).

You can make the dimming less severe by using a higher voltage for your supply (6 or 7.5v). I don't know how noticeable it will be but it may even be kind of nice to have them toned down

Note, some traces moved but I circled the key changes. Just diodes need to be added.

danadak said:

If the drive levels are not adequate, and he has to mod the circuit, why not unsolder the vanilla part
and put in the solution ?

Click to expand...

Because he wouldn't be able to goose the voltage beyond 7v with a 74-series part. See my solution to his modification request.

JDGafford said:

When I connect 13 to 16, it shuts down the circuit.
Using your original diagram you gave me, and putting pin 13 to ground, here is what I get....

LED #1 comes on....stays on for 1.4 seconds and turns off.
LED #2 comes on .7 seconds after LED #1 turns off and stays on for 1.4 seconds.
LED #3 comes on immediately after LED #2 turns off, flashes twice and turns off.
Then the circuit resets.

So, is it possible to have #1 and #2 to turn on and stay on throughout the duration of the circuit?

And, is there a way to have LED #3 to turn on 1.4 seconds after LED #2 comes on and blink 6+ times before turning off and resetting the circuit?

Also, I can't use 3 inputs on the first and second bank of LED's.
If I use 2, it will illuminate, but it's dim.
If I use 3, it wont illuminate at all.
Im using only 1, 3 volt white light LED with no resistor.
using 2 LED's dims them both unless i bump up the input voltage to 6 volts.

Thank you again for all your help.

Click to expand...

The 4017 (either the CD or the 74HC version) has up to 10 discreet operating states.

I suggest creating a table of what you want to happen for each of those states. The table will have 10 rows and look something like this:

State LED1 LED2 LED3
0 on off off
1 on off off
2 off on off
-
-
9 off off off

You can get more than 10 states, but will need more circuitry, such as a second 4017 and some extra gating logic. Or a microcontroller.

As danadak mentioned, the 74HC version of the part has higher output current, and would be an improvement for a 5 Volt system. Personally, I would add 3 2N7000 mosfets and switch the low side of the LEDs. That would make the output drive current of the 4017 almost irrelevant.

danadak said:

The CD74HC4017 drive level looks like -

View attachment 149822

Click to expand...

No, they do not. And implying to anyone that it is ok to use Absolute Maximum Ratings as design parameters, especially someone not experienced enough to know how dangerous that can be, is dangerous.

The image in post #10 shows that the OP purchased a CD4017B, not a CD74HC4017. The original 4017 part has lower current ratings for both the Absolute Maximums and normal operation. Here is the datasheet for the CD4017B. This is the original datasheet composed by RCA. Note the Output High (Source) Current on page 3 for the 5 V condition.


ak

AnalogKid said:

No, they do not. And implying to anyone that it is ok to use Absolute Maximum Ratings as design parameters, especially someone not experienced enough to know how dangerous that can be, is dangerous.

The image in post #10 shows that the OP purchased a CD4017B, not a CD74HC4017. The original 4017 part has lower current ratings for both the Absolute Maximums and normal operation. Here is the datasheet for the CD4017B. This is the original datasheet composed by RCA. Note the Output High (Source) Current on page 3 for the 5 V condition.

https://www.ti.com/lit/ds/symlink/cd4017b.pdf?ts=1747221523189&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FCD4017B%253Futm_source%253Dgoogle%2526utm_medium%253Dcpc%2526utm_campaign%253Dasc-int-null-44700045788370278_prodfolderdynamic-cpc-pf-google-eu_en_int%2526utm_content%253Dprodfolddynamic%2526ds_k%253DDYNAMIC+SEARCH+ADS%2526DCM%253Dyes%2526gad_source%253D1%2526gad_campaignid%253D19986097158%2526gbraid%253D0AAAAAC068F1tKayQi67_GgACGJe8CPHGq%2526gclid%253DCjwKCAjw_pDBBhBMEiwAmY02NjGzMpZ_mPre2Hxa4CLObVU72UB3fO-Sd_-S9fUtZgUkstECDbN2aRoCTioQAvD_BwE%2526gclsrc%253Daw.ds

ak

Click to expand...

The datasheet I looked at, and most others, between manufacturers, have limited
specs. The absolute maxes, are guidance, limits, but one surely can infer more than
1 mA would fly. I even found a 74HC datasheet with 50 mA max total Vcc current.

But this is all moot given we do not know how much current already being consumed
be existing unmoded board, current available for driving more additive loads, eg. driver
solutions. Or for that matter what the Voh worst case is in existing unmoded design.
Eg. need for external driver solution, specs over T and V......

Is the 20+ year old datasheet, Harris, you posted is that process still being manufactured ? Is it
even advisable to be working off that datasheet ? A question for the chosen manu-
facturer.....

How did you determine this ?

someone not experienced enough to know how dangerous that can be, is dangerous.

Click to expand...

But I would agree I should have clarified the post with the maxes and what it
can and cannot be used for.

The image in post #10 shows that the OP purchased a CD4017B, not a CD74HC4017.

Click to expand...

Yes, we all agree to the obvious.

The OP has stated solution must be additive, no mod of original board other than
add circuits to drive additional LEDs. The ULN2803 and 2N7000 approaches right
direction but specs at 25C and incomplete specs not helpfull.

danadak said:

no mod of original board other than
add circuits to drive additional LEDs.

Click to expand...

What? What "original board" are you talking about?

ZipZapOuch said:

What? What "original board" are you talking about?

Click to expand...

Post #9 ? Diorama already made/designed..... I took this to be original base board
of system.

danadak said:

Post #9 ? Diorama already made/designed..... I took this to be original base board
of system.

Click to expand...

A diorama is not an electronic device.

ZipZapOuch said:

Ok, try this... but, when rediculous speed comes on, the light speed sign will dim a bit.

When the ludicrous speed sign comes on, the rediculous sign will dim a bit (but the light speed sign will NOT dim more).

You can make the dimming less severe by using a higher voltage for your supply (6 or 7.5v). I don't know how noticeable it will be but it may even be kind of nice to have them toned down

Note, some traces moved but I circled the key changes. Just diodes need to be added.

View attachment 149823

Click to expand...

ZipZapOuch said:

Ok, try this... but, when rediculous speed comes on, the light speed sign will dim a bit.

When the ludicrous speed sign comes on, the rediculous sign will dim a bit (but the light speed sign will NOT dim more).

You can make the dimming less severe by using a higher voltage for your supply (6 or 7.5v). I don't know how noticeable it will be but it may even be kind of nice to have them toned down

Note, some traces moved but I circled the key changes. Just diodes need to be added.

View attachment 149823

Click to expand...

When I made up this circuit, I did not include extra diodes in line with the LED's as this schematic showed. As the LED's were diodes already.
Since I'm not familiar with these types of circuits, can you explain the purpose of the diodes in the original schematic and what the additional diodes will do?
Also, any certain value diode I need to use?