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rapidly flashing LEDs

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Fviking

New Member
HI;
I was an electronics teck in the USArmy when everything had these orange glowing glass tubes that got very hot. So I know basics.
A man i met at the Local Hobby Shop is building a RC model P38 Fighter plane with a 9 1/2' foot wing span. He was a fighter pilot in WWII and flew, you guessed it, P38s.
The P38 had 4 machine guns and one cannon, 20mm I believe, all located in the center pod with the pilot. My Pilot friend wants to have bright rapidly flashing white LEDs or orange or yellow, in each barrel to simulate firing. He will have a sound system too.
The references I have found on the web are mostly low power red and don't flash fast, more like 2 a sec. which might be OK for the canon but the machine guns are much faster. Or so old that the sources they quote are gone.
There will be 12v or more available on the plane, it is an electric powered plane, or a few subC cells won't bother the overall weight of the plane.
What I need is a simple flasher i can repeat 4 or five times or one that flashes 2 LEDs alternately ( would build two) I don't want any of the light to flash at the same time as another.
Sounds easy, any help will be greatly appreciated;
That Fviking.
 

HarveyH42

Banned
A 4017 counter has 10 outputs, only one on at a time, use the fifth output to trigger a reset, if you want just 4 LEDs. You could use a couple off 555 timers, one to clock the counter chip, and one to set how many times the counter cycles.
 

Boncuk

New Member
I guess machine guns firing at a fixed sequence isn't quite the right idea. The pilot normally selects the weapons to use. If he selects all none of them will fire at the same time as the other.

I suggest to use two dual timer ICs and activate them independently. This would mean at least two extra R/C channels.

The same result can be achieved using one R/C channel and step through gun selection using a decoder circuit. (which might be a decimal counter with its outputs wired accordingly using a diode network.)

Use the counter outputs to set/reset each individual timer with the clock signal being supplied by one R/C channel.

The sequence would then be: trigger once - gun1 fires, trigger twice - guns1 and 2 fire and so on up to trigger 5 which deselects all weapons.

Boncuk
 

ccurtis

Well-Known Member
Hi Ccurtis; There are switches available (electronic) that plug into the receiver in a unused channel and work with a switch on the transmitter.
Okay! So if I understand correctly, you very simply need a circuit that flashes an LED as a rapid-fire rate (say 4 times per second). The same circuit is used four times; one circuit for each gun. The firing of each gun is performed by remote control of a switch on the aircraft.

If that is correct, the only thing missing is the details of the remote control switch; i.e. can the remote controlled switch supply power to the flasher circuit directly, or does it provide a low current logic level, incapable of powering the flasher circuit directly and thus requiring a driver in the circuit. If the later is the case, then the logic levels (high and low) should be known.
 

ccurtis

Well-Known Member
Hi Ccurtis;
I haven't had my hands on one of the switches, they are back ordered.
If the current requirements are low 0.5A or so that can be supplied by the receiver at 5V. Otherwise it can switch on current from a battery of any necessary size, Sub Cs, AA, A, Like 5- 4000mAh subC for 6V, or 8- 2/3A for 9V.
Okay. There are quite a number of ways to flash an LED. When you did your search did you find a circuit that was particularly well suited? Most flasher circuits can be adjusted and we can help you determine what adjustments to make. Do you have a preference for ICs vs. discrete parts, like transistors?
 

Boncuk

New Member
Hi Fviking,

before this threat becomes an endless discussion about parts you might or might not have here is a suggestion for a circuit.

The circuit can be operated by connecting a microswitch to a servo and a cam. Each time the servo deflects toward the microswitch the counter advances by one count. (Servo has to be set to neutral after activation)

The diode network switches on one more gun with each clock cycle until all four guns are "firing". To seize fire activate the servo another time.

IC1 takes care of proper switch debouncing.

If space is an issue I suggest to use an MCU.

Regards

Boncuk
 

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Fviking

New Member
flashing

Hi Boncuk;
Thanks a bunch for that circuit.
Most times the simplest answer is the best. RadioShack used to sell a kit to make LEDs flash. Unfortunately they discontinued it some years ago and at my local RS store they don't even have the parts to build one.
Here is a link to the 2 circuits that I have found.
Simple LED flasher circuits
Thanks;
Fviking
 

Fviking

New Member
Flashing

Hi Ccurtis;
I had a chat with the Pilot and he has his engine sound and Machine Gun sound systems. Both run on 9v and he is switching them with a servo and a micro switch. So a 9v system would be nice. Like the first flasher.
Here is the link to the info I have found that best suits my needs, I think.
I could be wrong I haven't built one yet.
Simple LED flasher circuits
I am new to this area and don't know if there is a parts supplier close.
I am checking;
Fviking
 

Boncuk

New Member
Hi Boncuk;
Thanks a bunch for that circuit.
Fviking
Hi Fviking,

your friend certainly won't want to install a circuit to "fire" guns precisely alternating.

I guess he wants to have the "muzzle fire" as close as possible to the real thing.

I have no info about the P38 gun rate of fire (ROF) and assumed 600 rounds per minute. (10 flashes per second and per gun). For a slower ROF use 1µF caps for C2 through C5, resulting in 5 flashes/s (300 rounds/minute), or to increase ROF use 0.22µF instead for 21 to 22 flashes/s (approx. 1250 rounds/minute).

If you are intersted in building the suggested circuit you might contact me via email (use "[email protected]") to obtain both, schematic and PCB-layout in Eagle format.

The board size is 2.750X2.450inches, including all external connections using solder pads.

Other than marked (+5V) on the PDF file a supply voltage of 4.8V might be used. The current limiting resistors are calculated for Uf=2.2V, If=20mA, and supply voltage=4.8V.

Regards

Boncuk
 

ccurtis

Well-Known Member
Hi Viking. The circuit you linked too is simple enough, and I take it that simple is what you are after. Each LED (gun) can be made to flash alternately at about a 5 times per second (5 Hz) rate by changing the 100K resistors to 30K. You can use 2N2222 transistors if they are easier to come by. All of the parts should be available at Radio Shack.

Each LED will have the same ON time as OFF time. A more realistic firing is a short ON time with longer OFF time. That can be achieved by replacing the left side LED with a short circuit, replacing the left side 470 ohm resistor with a 10K resistor, replacing the right side 100K resistor with a 10K resistor. Then you will have a 5Hz flash rate and a short pulse of light for the LED on the right side. That circuit would have to built for each gun, obviously, since it only has one LED then. I suggest getting resistors of various values to get the rates you want.
 
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Fviking

New Member
Circuits

Hey Ccurtis;
Thank you ! That is great.
I am a strong proponent of the KISS principle.
I will try the RS in the next town and see if they have more parts. I looked at Newark.com and the array of variations of the same part was staggering. There were 6 or 8 different 2N3904s, I could figure the resistors, but the caps(wow) there are lots of new types, new to me anyway .
I will get on that today after I finish my present project, I am building a model plane for some guy with more money than time. Getting paid for you hobby is great.
Thanks again;
Fviking
 
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