Single pulse trigger for LED sequencer with 555 and 4017

Thread Starter

Sheldee

Joined Jun 19, 2023
3
I have seen a lot of circuits for an LED sequencer using a 555 and 4017 but all rely on a continuous power supply to cascade or a N/O switch to step sequenctially from Q0 to Q9. (See attached as an example circuit).
I am building a pinball machine and the attached circuit, which allows variable timing is what I need to pulse a row of 9 LED' without repeating.

My problem is that I want to trigger the circuit by the ball rolling over a normally closed switch contact.
I have a 555 circuit that works one-shot with a normally closed contact, to operate a relay when the N/C contact opens.

I want this relay pulse to trigger the 555 and 4017 sequencer circuit but the circuit must sequence once through the 9 LED's even though the trigger pulse has restored. It would reset after the ninth LED and wait for the next pulse to start again.

I would be grateful for any suggestions if this can be done.
 

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ElectricSpidey

Joined Dec 2, 2017
2,832
Your request is confusing.

Do you have a dry contact NC switch you want to operate this circuit, or is this switch already part of another circuit?

Or do you want the relay to start the sequence?

Would it be ok if the one-shot started the sequence?
 

ElectricSpidey

Joined Dec 2, 2017
2,832
Ok, here ya go.

This circuit is if you have access to the existing 555 one-shot output.
V2 is the existing one-shot.

AAC_Pinball_NC_Sequence.JPG

This circuit is for a dry contact NC switch.
The dotted outline is the switch.

AAC_Pinball_NC_Sequence_2.JPG

LED drivers connect to outputs Q1 thru Q9.

AAC_Pinball_NC_Sequence_Wav.JPG

This circuit uses 1/2 of the 4013, tie the unused inputs of the second one to ground.
Leave all unused outputs open.
Power connections to the 4013 and 4017 not shown.
 
Last edited:

Thread Starter

Sheldee

Joined Jun 19, 2023
3
Ok, here ya go.

This circuit is if you have access to the existing 555 one-shot output.
V2 is the existing one-shot.

View attachment 296955

This circuit is for a dry contact NC switch.
The dotted outline is the switch.

View attachment 296956

LED drivers connect to outputs Q1 thru Q9.

View attachment 296957

This circuit uses 1/2 of the 4013, tie the unused inputs of the second one to ground.
Leave all unused outputs open.
Power connections to the 4013 and 4017 not shown.
Many thanks, ElectricSpidey.

This is exactly what I was looking for.
I breadboarded it and it worked first time. When the microswitch is pulsed, the LED's go through one cycle and then switch off.
I modified the circuit slightly by replacing the 10k resistor across 6 and 7 of the timer with a variable 10k resistor.
This will enable me to adjust the sequence frequency of the LED's to the speed of the ball passing over the microswitch.

Again, you are a star.
 

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