Alternating Flashing Pattern with 555 timer and ONLY one set of LEDs

Thread Starter

Henksmit

Joined May 1, 2017
7
Hi, I am new to the forum and also electronics and cannot remember most of what I have learnt about electronics in high school.

I want to build a warning beacon using LEDs. Attached is a diagram that I finally got working after a few hours.

The idea is to have a few (not sure how many) LEDs flashing in flip-flop fashion once every half second and then change to one flash every 1.5 seconds. BUT, I do not want two separate sets of LEDs like I have in my circuit, this is going to take up too much physical space. I want to use the same LEDs for bot the 555 timers.

Once this works I want to go one step further and change the timer in yellow section to drive a 4107 to have a chasing light for a few seconds followed by flashing lights and so on. But I am not there yet.

I hope my question is clear? I will really appreciate any advice.
 

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AlbertHall

Joined Jun 4, 2014
12,328
You could use the first '555 to switch a different timing capacitor for the LED flasher.
Use a 2N7000 MOSFET. Connect its gate to the output of the first '555. Connect its source to 0V. Then use one of the LED flasher circuits permanently connected to the power supply with the 50k timing resistor and 5uF capacitor. Then connect a 50uF capacitor between the drain of the MOSFET and pins 2 and 6 of the flasher '555, negative to the MOSFET drain.

This arrangement will switch the timing capacitor between 5uF and 55uF (the two capacitors in parallel).
 

Bernard

Joined Aug 7, 2008
5,784
Wouldn't switched C be more like 10 uF?
Yellow: Did you mean 4017, decade counter ? Lots of problems if using same LEDs.
 

EM Fields

Joined Jun 8, 2016
583
Hi, I am new to the forum and also electronics and cannot remember most of what I have learnt about electronics in high school.

I want to build a warning beacon using LEDs. Attached is a diagram that I finally got working after a few hours.

The idea is to have a few (not sure how many) LEDs flashing in flip-flop fashion once every half second and then change to one flash every 1.5 seconds. BUT, I do not want two separate sets of LEDs like I have in my circuit, this is going to take up too much physical space. I want to use the same LEDs for bot the 555 timers.

Once this works I want to go one step further and change the timer in yellow section to drive a 4107 to have a chasing light for a few seconds followed by flashing lights and so on. But I am not there yet.

I hope my question is clear? I will really appreciate any advice.
So, as understand it, if you have an 8 LED array you'd like one set of four LEDs to be ON and the other set of four to be OFF for half a second, and then have them trade places every half a second for a while.

Next, you'd like for the entire array to turn ON for 1.5 seconds and then turn OFF for 1.5 seconds and then multivibrate like that for a while.\

Finally, you'd like a "chase" sequence to occur for a while and then have the beacon start over with the initial sequence and repeat the three steps forever.

Am I right?
 

Thread Starter

Henksmit

Joined May 1, 2017
7
So, as understand it, if you have an 8 LED array you'd like one set of four LEDs to be ON and the other set of four to be OFF for half a second, and then have them trade places every half a second for a while.

Next, you'd like for the entire array to turn ON for 1.5 seconds and then turn OFF for 1.5 seconds and then multivibrate like that for a while.\

Finally, you'd like a "chase" sequence to occur for a while and then have the beacon start over with the initial sequence and repeat the three steps forever.

Am I right?

I would like to have two sequences with one array of 8 LEDs. If all goes well, both sequences will be using the same LEDs.

Sequence 1 - i want 4 on and then the other 4 on in a flip-flip fashion.

Then in Sequence 2 i want the 8 leds chasing each other.

I was hoping to have 3 variable resistors to change the times for on and off.
 

EM Fields

Joined Jun 8, 2016
583
I would like to have two sequences with one array of 8 LEDs. If all goes well, both sequences will be using the same LEDs.

Sequence 1 - i want 4 on and then the other 4 on in a flip-flip fashion.

Then in Sequence 2 i want the 8 leds chasing each other.

I was hoping to have 3 variable resistors to change the times for on and off.
How long do you want sequence 1 to last?

Then, how long do you want to wait between hits in sequence 2 and how many cycles of sequence 2 would you like to be accomplished until sequence 1 is again initiated?
 
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Bernard

Joined Aug 7, 2008
5,784
I didn't think that it was practical to use same LEDs for flashing & chasing but here is an outline that I think will do it. Not sure of LED color. or timing. If control, U1-4, is high, There is a glitch in the 2N3904 circuit, will save till morning, but on with the show. U1-4 high, pin 3 is oscillating 0 V to 8V; when hi, lower LED are on ( missing invertor @ base ) , upper LEDs off. Control low, U1 resetU2 enabled. It's late but will post the general idea with
flaws.Multi Flasher #1 00000.jpg
 

Thread Starter

Henksmit

Joined May 1, 2017
7
I didn't think that it was practical to use same LEDs for flashing & chasing but here is an outline that I think will do it. Not sure of LED color. or timing. If control, U1-4, is high, There is a glitch in the 2N3904 circuit, will save till morning, but on with the show. U1-4 high, pin 3 is oscillating 0 V to 8V; when hi, lower LED are on ( missing invertor @ base ) , upper LEDs off. Control low, U1 resetU2 enabled. It's late but will post the general idea with
flaws.View attachment 125902

Thanks Bernard
I will give it a go. Will let you know how it worked.
 

Thread Starter

Henksmit

Joined May 1, 2017
7
How long do you want sequence 1 to last?

Then, how long do you want to wait between hits in sequence 2 and how many cycles of sequence 2 would you like to be accomplished until sequence 1 is again initiated?
EM, I have to be honest, have not thought about the timings yet. At this stage it is more about getting the LEDs to go on and off, hence the reason for thinking about variable resistors.
 

Thread Starter

Henksmit

Joined May 1, 2017
7
Hi all
Maybe an update on why I want to build this and what it will be used for.

I live in a more rural area in South Africa with a fairly busy national road going through our area, with a lot of accidents on the road. Due to the fact that our Police Service is terribly understaffed they rely heavily on Community Policing Forums, which I am part of. We assist the police on a volunteer basis with non-violent issues.

Securing and making road accident scenes form a big part of what we do, but again we do not get any resources to do it with.

The idea with the LEDs is to make some form of electronic road flare that I can leave on the road, before the accident as a warning. The ideal would be to get traffic cones and put it under the cone to light up the whole cone.

To draw more attention I dont want them to have one blinking pattern, hence the reason for two blinking sequences, but the timing will be finalised as time goes on. The units, once complete must be stored in my car somewhere, so must be as small and compact as possible.

So, budget and size is critical as I will have to make a lot, for myself as well as other members helping out.

Thanks a lot for the assistance.
 

AlbertHall

Joined Jun 4, 2014
12,328
This is getting to the point where it would be a lot easier and smaller and more adaptable to use a microcontroller. Most will directly drive LEDs and if you change your mind about timings or which LEDs should be which part of the sequence you just need to change a text file and program it into the uC.
 

Thread Starter

Henksmit

Joined May 1, 2017
7
This is getting to the point where it would be a lot easier and smaller and more adaptable to use a microcontroller. Most will directly drive LEDs and if you change your mind about timings or which LEDs should be which part of the sequence you just need to change a text file and program it into the uC.
Albert
Although it sounds nice (I am a programmer by trade) I am not completely in the dark. While realising someone else cannot do it FOR me, I do want to ask what can I read up on? Is there a specific product or code that I can look for?

Thanks
 

Bernard

Joined Aug 7, 2008
5,784
Revision of post # 9. This outline assumes LED current of about 10 mA ea. You might need to make some tests to see what LED brightness works best & then determine what battery power is required. Are batteries to be rechargeable? Might drop battery to 6 V.
When control is high, U1 is active, delivering alternate flashing, U2 held at reset. Control low, U1 held at reset,
U4 non conducting, U2 active, LED sweep 1 to 8 & start over. If upper set of LEDs is rewired in inverse order , sweep will be bidirectional.
Timing: U1 1/2 sec. each state, U2, 4 cycles / sec., control, 5 sec. ea. state ?Multi Flasher #2 00000.jpg
 

AlbertHall

Joined Jun 4, 2014
12,328
Albert
Although it sounds nice (I am a programmer by trade) I am not completely in the dark. While realising someone else cannot do it FOR me, I do want to ask what can I read up on? Is there a specific product or code that I can look for?

Thanks
What are you used to programming - embedded?
I use assorted PICs so I know them fairly well.
 

Thread Starter

Henksmit

Joined May 1, 2017
7
What are you used to programming - embedded?
I use assorted PICs so I know them fairly well.
Initially started on Basic, Pascal, VB etc. now in the automation and instrumentation, so leaning more towards ladder and one puece of equipment that we work with is pretty much old machine code.

I have been looking at Arduino, programming seems really easy? And they are freely available.

Will that also work?
 

AnalogKid

Joined Aug 1, 2013
10,943
Sounds like a good little project.

First, a traffic cone is pretty thick plastic, and almost opaque. Putting the LEDs inside might not get you the external brightness you need.

Second, if the LEDs are inside a traffic cone, what does a chaser pattern get you? Again, things will be far less distinct outside the cone. For that matter, flip-flopping between two LED groups would be great if they were in two different traffic cones, but inside the same cone, probably not.

Third, combining a chase pattern with just about anything is messy without a microcontroller- not terribly complicated, but lotsa parts. Since buying a commercial safety flasher unit is out, I recommend alternating between two noticeably different 50-50 on-off flashing speeds, such as 1 Hz and 5 Hz. Two or three cones never will be synchronized, and the apparently random pattern changes among the group will be very attention-getting.

Two 555's, or one CD4093 plus a 2N7000 transistor can do this. The 555 won't need a driver transistor unless the LED current is above 150 mA. With a 9 V battery and a 2 V drop per LED, 9 LEDs in three strings of 3 each would need 120 mA.

ak
 

EM Fields

Joined Jun 8, 2016
583
Hi all
Maybe an update on why I want to build this and what it will be used for.

I live in a more rural area in South Africa with a fairly busy national road going through our area, with a lot of accidents on the road. Due to the fact that our Police Service is terribly understaffed they rely heavily on Community Policing Forums, which I am part of. We assist the police on a volunteer basis with non-violent issues.

Securing and making road accident scenes form a big part of what we do, but again we do not get any resources to do it with.

The idea with the LEDs is to make some form of electronic road flare that I can leave on the road, before the accident as a warning. The ideal would be to get traffic cones and put it under the cone to light up the whole cone.

To draw more attention I dont want them to have one blinking pattern, hence the reason for two blinking sequences, but the timing will be finalised as time goes on. The units, once complete must be stored in my car somewhere, so must be as small and compact as possible.

So, budget and size is critical as I will have to make a lot, for myself as well as other members helping out.

Thanks a lot for the assistance.
@Henksmit: Here's a preliminary hardware design that uses a couple of quad 2 to to 1 muxers (switching the 8 nodes between modes 1 and 2) which will do what you say you want to do, and if you can specify the timing I'll go ahead and finish the design so you can determine whether you want to proceed with hardware + software or just hardware.
Traffic cone illuminator..png
 
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