Looking to setup a burst fire circuit

Thread Starter

He-Man

Joined Dec 26, 2018
5
I'm curious to know how to connect a circuit to allow for an effect like the following video at 24 seconds in.




I've been looking into the 555 timer and simulating it in this online simulator.
http://tinyurl.com/ybhdfze9
But when looking online for circuits to learn from, this online simulator doesn't have a ground pin for the 555 timer and I don't get how to connect it properly. The circuit I linked to is one of the example circuits that comes with the simulator. I simply just added a push switch.

Basically the function I'm after is the following:
1. press the trigger, a led is flashing 3 times.
2. hold the trigger, a led is flashing three times, then there's a short pause(1/2 sec) and it repeats.

Hi by the way I'm new here! =)
 

WBahn

Joined Mar 31, 2012
29,979
Many simulators do not implement power/ground pins of logic chips -- they assume that all logic shares the same power and same ground and that it is sufficient to have outputs that are HI or LO (a logic state as opposed to a voltage). This is particularly true of the simpler simulators. Some simulators have settings that allow you to control this so that you can deal with at least some situations in which this is a bad assumption.

You'll probably need to delve into the documentation on the simulator you are using to sort it out.

Another option is to use a real simulator, such as LTSpice, which is free.
 

Thread Starter

He-Man

Joined Dec 26, 2018
5
Thank you so much! That explains it.
Can you give me any pointer as to what components I should look into. Would I be able to accomplish what I want with two 555 timers? Or is there a better approach?
 

AnalogKid

Joined Aug 1, 2013
10,987
A problem with the 555 in this type of circuit is that the first flash will be longer than the later pulses. This is because the minimum voltage on the timing cap is 0 V at the start, but Vcc/3 for later cycles. This will affect both the higher rate oscillator for the flashes and the lower rate oscillator for the on/off cycles.

As an alternate approach, look into the CD4017 Johnson Counter chip. That plus 3 signal diodes and one output transistor will deliver the pattern you want when driven with a 555 oscillator circuit.
ak
 

WBahn

Joined Mar 31, 2012
29,979
Thank you so much! That explains it.
Can you give me any pointer as to what components I should look into. Would I be able to accomplish what I want with two 555 timers? Or is there a better approach?
That depends entirely on what your metric of "better" is. What is important? What is not?

It also depends on what your resources are. I'm guessing you don't have any background in dealing with microcontrollers? What about programming in general? Is it something you would be interested in learning? If not, then the time, effort, and cost (though none are by any means outrageous) is probably not worth it, but that approach has a lot going for it. There are other approach, such as the notorious Arduino, that might be a good fit for what you are trying to accomplish.
 

Thread Starter

He-Man

Joined Dec 26, 2018
5
Thank you @AnalogKid. I'll look into those components.
And thank you @WBahn. Very good questions. I'm kinda familiar with Arduino and I do program so I should be able to set it up using a micro controller, but for the sake of learning I wanted to be able to see how something like this is created with a circuit and how small I could make it.

MOD NOTE: Added notification tags to the member names. This results in the user receiving an alert (depending on their settings) with a link to this post. No need to boldface the names for this to work.
 
Last edited by a moderator:

Thread Starter

He-Man

Joined Dec 26, 2018
5
Thank you very much for the suggestions. The reason I am inquiring about whether it can be done with a small circuit and minimal components is cause I had this robocop action figure from back in the day which I found that comes with this flashing light and sound, but it it continuously. The circuit only consists of a transistor and a resistor. I was wondering if there could be a setup which would fit into the same figure, but I can see that might be impossible.
 

djsfantasi

Joined Apr 11, 2010
9,156
Wow, I am looking for this exact effect for a play that I am writing to be presented in competition. Will follow this closely.
One thing that isn’t clear is how are the sounds being produced?
@danadak Your link is exactly the kind of thing I was looking for in my other post today. I had forgotten about the ATTINY85!
 

Thread Starter

He-Man

Joined Dec 26, 2018
5
Wow, I am looking for this exact effect for a play that I am writing to be presented in competition. Will follow this closely.
One thing that isn’t clear is how are the sounds being produced?
@danadak Your link is exactly the kind of thing I was looking for in my other post today. I had forgotten about the ATTINY85!
The sound is to the best of my judgment connected in parallel to the led so they'll fire off at the same time. I'll take a photo and post the circuit for you all soon.
 
Top