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CD4017B: Cascade timer for 20 to 80 lights

Gerald
Genius 9570 points
Part Number: CD4017B
Other Parts Discussed in Thread: CD4514B, CD4510B, SN74HCS74, SN74HCS164

Hi Experts,

Our customer is looking for a schematic for the CD4017B cascade timer for 20 to 80 lights. He have a few circuits he got off the internet, but they allow 4 lights to be on at the same time running together.

It is a so-called chaser or sequencer is one of the most popular types of LED-driving circuit and is widely used in advertising displays and in running-light ‘rope’ displays in small discos, etc. Driven by a 555 timer and cascades the lights. The circuits he has found do not work properly.

I cannot find the data to show how to cascade the 4017 for multiple 4017s. He uses the 555 timer for Pulse Wave Modulation for motor speed control by adjusting the duty cycle and can set the circuit for an adjustable pulse rate to adjust the speed of the chaser.

He was hoping we would be able to simply give him the schematic he need. He said: is this too complicated of an issue for TI? Or should I just expect to only make chaser lights of 10 maximum?

I hope you can help us. Thank you.

Best regards,

Gerald

  • +1
    Guru 285290 points

    It might be possible to combine two BCD counters (CD4510B) and many decoders (CD4514B), with the most-significant-digit decoder selecting which of the other decoders is active.

    Alternatively, just cascade many shift registers (SN74HCS164), and use one or more flip-flops with /PRE input (SN74HCS74) so that you have some active bit(s) after reset.

  • +1
    TI__Guru* 96862 points

    Hey Gerald,

    I would expect the best solution with modern design to be a dedicated MCU plus multiple shift registers to provide the best results. This would allow for much more customizability in the appearance of the LEDs - for example being able to fade on or fade off LEDs to improve the appearance of the 'chaser'.

    If the customer truly only wants a simple chaser, the recommendations from Clemens would work. I'll see about providing an example solution today - please check with the customer if an MCU is a possibility or if they really prefer a 'simple' logic solution.

  • +1 in reply to Emrys Maier
    TI__Guru* 96862 points

    I put together a quick diagram that should give enough details to follow. I only showed three shift registers below, but any number can be used to get as many outputs as are desired. I recently published an application report that details issues that can arise when using many shift registers in series like this. Please see Designing with Shift Registers for additional information.

    One mistake I just caught -- the output of the D-type flip-flop is the first output rather than O_0, giving 25 total outputs from the above circuit.

  • 0 in reply to Emrys Maier
    TI__Genius 9570 points

    Hi Emrys,

    Please see below for our customer feedback prior to your response with diagram above:
    "So, you are guessing?? I said I have tried dozens of circuits and they do not work. I have used TI components for decades, but I am disappointed you have not asked engineering for the full schematic. I have tried diodes and AND gates to isolate to only one light on at a time with zero luck. That's why I asked TI for the solution. Maybe Fairchild or NPX could answer my simple question?? It may be a freshman question, but no one has the answer, only guesses, apparently including TI."

    I will update you once I received a feedback again from the customer. Thank you so much.

    Best regards,

    Gerald

  • 0 in reply to Gerald
    TI__Guru* 96862 points
    Gerald said:
    So, you are guessing??

    I'm a bit confused on how the provided diagram can be considered a guess. Perhaps they are referring to Clemens's response including "It might be possible to..." -- is the customer aware of how forums work? Clemens is a very accomplished engineer and helpful community member, but he is not a TI employee.

    I would recommend sending the customer to this forum directly so we can discuss with him -- I don't see the purpose of having this game of 'telephone' between engineers.

  • 0 in reply to Emrys Maier
    TI__Genius 9570 points

    I agree with you. I also see many posts that Clemens is very helpful in this community. The customer is using a yahoo account but I will try to ask if he has a valid company email so that he can post directly here in the E2E forum. Again, thank you very much both for all the help.