Newbie needs help (LED "Flashbang" project)

Thread Starter

Cheerful_Scumbag

Joined Nov 20, 2022
10
I was looking at making my own LED flashbang for a project and stumbled upon this thread old thread.
https://forum.allaboutcircuits.com/threads/newbie-needs-help-led-flashbang-project.113907/
I wonder if op finished his flashbang. I would love to see the result.

I plan to model and 3d print a case with 3 cob led in it and a siren.
I have a some 30v COBS Leds somewhere in the garage that I plan to dig out and and use if possible but i think they might be a bit to hungry to power off a 11.1v LiPO.

I have found a video of someone disassembling a flash bomb I would like to base my project on. would a helpful person be able to help me understand how this one works?
I think it must be using a micro controller.
the cobs are discontinued and I can't find a datasheet but the Ali express say they are AC 12v COB. dumb question, is the circuit
https://www.aliexpress.com/item/4000253318441.html converting 11.1v LIPO dc to ac, or is this irrelevant?
Would this circuit be simple to reverse engineer or should i stick to 555 timers like the previous guy did?
would anyone be willing to help me with the schematic using 11.1v power source with 3 12v or 30v cob leds and a siren? it would be very much appreciated.
Thanks
 

WBahn

Joined Mar 31, 2012
27,893
MOD NOTE: You already have a thread that was split off and started for you on this topic. However, that thread got derailed, so the best solution is to let this one continue and close the other one.
 

Thread Starter

Cheerful_Scumbag

Joined Nov 20, 2022
10
Hi I apologise. But I didn't know that a new one was started. I hadn't got any notification. All I saw was, my post was deleted and the old thread was locked. Do you have a link to the thread you started feel free to delete this one if you want.
 

WBahn

Joined Mar 31, 2012
27,893
Hi I apologise. But I didn't know that a new one was started. I hadn't got any notification. All I saw was, my post was deleted and the old thread was locked. Do you have a link to the thread you started feel free to delete this one if you want.
Not a problem. This thread will do fine because the other one got a bit polluted with members talking about why it was split, so best to leave that one locked and use this one.
 

Reloadron

Joined Jan 15, 2015
7,080
I am seeing plenty of COB bright LEDs on amazon Just for example these 70Watt flavors. They should be brighter than the 50 watt at AliExpress which I see as not available. Albeit not quite inexpensive. :) If I were to build one personally I would just run with a ATTiny 85 or similar like a simple 8 pin dip PICAXE. To my way of thinking just easier and reduces parts count. I would use a logic level MOSFET to feed the LEDs. I would use a 7805 to drive my uC or maybe just a cheap buck converter. The latter is pretty inexpensive. For the mechanics of the spoon you are on your own. :) Oh yeah and for a loud wound I would find an old smoke detector and gut it.

Merely thinking out loud on this. Anyway these are my first thoughts.

Ron
 

Thread Starter

Cheerful_Scumbag

Joined Nov 20, 2022
10
I am seeing plenty of COB bright LEDs on amazon Just for example these 70Watt flavors. They should be brighter than the 50 watt at AliExpress which I see as not available. Albeit not quite inexpensive. :) If I were to build one personally I would just run with a ATTiny 85 or similar like a simple 8 pin dip PICAXE. To my way of thinking just easier and reduces parts count. I would use a logic level MOSFET to feed the LEDs. I would use a 7805 to drive my uC or maybe just a cheap buck converter. The latter is pretty inexpensive. For the mechanics of the spoon you are on your own. :) Oh yeah and for a loud wound I would find an old smoke detector and gut it.

Merely thinking out loud on this. Anyway these are my first thoughts.

Ron
That sounds like a good idea reducing parts is defiantly a pro due to the limited space. I like the idea of gutting an old smoke alarm.
A microcontroller like an attiny85 looks good but I'm no programmer so will have to research or have someone write the code on how to implement a delay and then activate strobing to 3 LEDs and a siren then reset after 5 clicks or something like that.
I wonder would you be so kind as to help me with the schematics of the circuit base on a ATtiny85
PS I have just found the locked thread the mod made and i really didn't mean to cause such a storm. I just wanted to talk to the op if he was still around and find out how his project turned out as well as build my own base off that thread.
 

Audioguru again

Joined Oct 21, 2019
5,418
When you buy the new COB LED from "over there" it is wrongly rated at 1 Volt.
Somebody, maybe on the old thread said 12VAC and others say 12VDC. I think 12VDC with your own current-limiting.

Current? some people say it cooks itself to death quickly but nobody says what kind and what size heatsink is needed.
It might survive a few short-duation blinks without a heatsink.
 

Thread Starter

Cheerful_Scumbag

Joined Nov 20, 2022
10
When you buy the new COB LED from "over there" it is wrongly rated at 1 Volt.
Somebody, maybe on the old thread said 12VAC and others say 12VDC. I think 12VDC with your own current-limiting.

Current? some people say it cooks itself to death quickly but nobody says what kind and what size heatsink is needed.
It might survive a few short-duation blinks without a heatsink.
The Ali express cobs I posted are just the one that are used for the device in the video. They are discontinued and wasn't going to buy them. I have a few bridgelux 35v cobs from another project that I powered by a meanwell led driver. Would I be able to use 3 of these and step the voltage up?
 

Reloadron

Joined Jan 15, 2015
7,080
That sounds like a good idea reducing parts is defiantly a pro due to the limited space. I like the idea of gutting an old smoke alarm.
A microcontroller like an attiny85 looks good but I'm no programmer so will have to research or have someone write the code on how to implement a delay and then activate strobing to 3 LEDs and a siren then reset after 5 clicks or something like that.
I wonder would you be so kind as to help me with the schematics of the circuit base on a ATtiny85
PS I have just found the locked thread the mod made and i really didn't mean to cause such a storm. I just wanted to talk to the op if he was still around and find out how his project turned out as well as build my own base off that thread.
While I am not a programmer type I dabble in it. Actually more like stumble along. :) My approach would be to map out on paper the sequence of events and delays. There isn't much there. Just about any 8 pin dip uC should work like a PICAXE 08M2 or ATTiny 85. On the bright side we do have a forum section for micro-controllers and several members who are very good at it. :) Again, this is just how I would go about it.

Ron
 

DickCappels

Joined Aug 21, 2008
9,512
It is amazing what you can do with an NE555 or three. If you can draw out the sequence you can probably come up with an NE555 based circuit to produce the sequence.
 

Thread Starter

Cheerful_Scumbag

Joined Nov 20, 2022
10
Pardon my delay in responding, I just haven't had the time this week.
I have decided I should use a microcontroller for this project as suggested by @Reloadron. the ATTiny85 will do nicely. this will reduce the number of components needed because the space available will be limited.

This will be the sequence of events:
A switch that when depressed, turns on the device with a 5 second delay. then it will start to strobe 4x high power LEDs and ring a loud siren from an old smoke alarm (good idea, thanks)
to stop the device the switch will be pressed and held down.

It will be powered by a 11.1v 3s LiPo battery
I want to use Bridgelux 40E4000-C-72 COB LEDs I have lots of them. It seems like a waste not to use them for this project.
the datasheet says the minimum voltage needed to power the is 33volts, so I will have to step up the power somehow

https://www.digikey.co.uk/en/products/detail/bridgelux/BXRC-40E4000-C-72/6181405


From my very limited understanding, I will need to step down the voltage for the ATTiny to 5v max and step up the voltage to 30v to run the cobs that will be in wired parallel. I'm not sure what voltage will be needed for the siren, so i might omit this for the time being.
Im stuck now on how to proceed, I don't know how to make the schematic. I don't no what components I need to provide the power and what MOSFETs i need etc

Thanks for all your replies
 

Audioguru again

Joined Oct 21, 2019
5,418
39W in one of those COB LEDs produces 4.4 times more light that in some rooms in my home. You will use four LEDs?
The 11.1V battery current for four LEDs plus heating the voltage stepup device will be about 16A!

I hope the blink durations will be short enough that huge heatsinks are not needed.
 

Reloadron

Joined Jan 15, 2015
7,080
OK here is what I suggest you do. I would start a new thread in this section of the forums. We have several people here who are really good with micro-controllers. Next to drive the LEDs you will need something, I suggest three MOSFETs to drive your LEDs like for example a FQP30N06L Logic Level MOSFET N Channel. Unless you are familiar with soldering and making a board in the interest of keeping things simple I would just buy an off the shelf and off the boat ATTiny proto module board. They are really inexpensive and the off the boat versions work just fine. A Google of ATTiny 85 module should bring up some results. With your 11.1 Volt battery, I assume Lipo battery pack keep in mind a few things. Most ATTINY 85 boards include a voltage regulator allowing for 5.0 volt or greater in to the board, I would just use a simple buck converter, again inexpensive. That gets your battery voltage down to a useable level. Boards like this and no problem using a 12 volt supply. Next problem is the ATTiny 85 will have a 3.3 volt out so to drive the MOSFETS a small scheme is needed but no big deal. Using a 5 volt logic uC like an Arduino Uno is just overkill.

Finally this is how I would approach things. There are other roads and all lead to Rome. What is real important is that you feel comfortable with the project.

Ron
 

djsfantasi

Joined Apr 11, 2010
8,672
An ATTiny 85 will run fine on 5V. So you can drive a logic Level MOSFET without “a small scheme”. You may need more power than the logic level MOSFET can control, but as I did you can use it to drive a power PNP MOSFET with enough power for your LEDs.

I realize you have 30V COB LEDs, but seriously consider finding some 12V ones. Boosting your battery to 30V will create a high battery drain. And with the ATTiny85, the current draw of the boost module might cause it to reset.

Let’s say you have found some 12V LEDs. You have an 11.1V battery. Good. You’d need a circuit or module to drop it to 5V for the ATTiny. You could use the full battery then to also power your LEDs. To do so, you’d need to make a driver circuit with a logic level N channel MOSFET (2N7000 or similar) and P channel power MOSFET (plus a resistor or two.

With your description of the sequence, depending on where you live, I could assist with the programming and mail you a pre-programmed chip to try.
 

Reloadron

Joined Jan 15, 2015
7,080
An ATTiny 85 will run fine on 5V. So you can drive a logic Level MOSFET without “a small scheme”. You may need more power than the logic level MOSFET can control, but as I did you can use it to drive a power PNP MOSFET with enough power for your LEDs.

I realize you have 30V COB LEDs, but seriously consider finding some 12V ones. Boosting your battery to 30V will create a high battery drain. And with the ATTiny85, the current draw of the boost module might cause it to reset.

Let’s say you have found some 12V LEDs. You have an 11.1V battery. Good. You’d need a circuit or module to drop it to 5V for the ATTiny. You could use the full battery then to also power your LEDs. To do so, you’d need to make a driver circuit with a logic level N channel MOSFET (2N7000 or similar) and P channel power MOSFET (plus a resistor or two.

With your description of the sequence, depending on where you live, I could assist with the programming and mail you a pre-programmed chip to try.
All good points. My bad too as I was looking at the ATTiny as a 3.3 volt chip and as djsfantasi mentions it's perfect at 5 volts. My take on the LEDs is they will be fired on a very short pulse duration, maybe a few milli-seconds. The MOSFET I suggested as an example is a 60V 30 Amp logic level MOSFET.

Ron
 

Thread Starter

Cheerful_Scumbag

Joined Nov 20, 2022
10
Blink duration will be short in the milliseconds as @Reloadron pointed out.
I'm very competent with soldering and building. it's the designing of the circuit and what components to use etc that i'm out of my depth with :)
I'm hoping to start a schematic over the weekend on miltisim if i get time. I will upload it to look over so I'm on the right track.
I don't want to use drop-in prototype boards because the space will be so limited I'm confident in making it when I know what it needs and what goes to what.

@djsfantasi I would like to use them as I have them. but you might be right, I'm a little out of my depth on the electrical engineering side so the simpler the better.
It's proving hard to find cobs around the 12v mark on sites like Farell, RS components and digikey the LEDs @Reloadron posted look to long.
I think I read that the minimum voltage my cobs take to power on is 20v if this helps.
I will definitely take you up on the offer of helping with the programming, god knows i need it. I'm In the UK so It might be better if I flash the chip.
Thanks everyone
 

djsfantasi

Joined Apr 11, 2010
8,672
Blink duration will be short in the milliseconds as @Reloadron pointed out.
I'm very competent with soldering and building. it's the designing of the circuit and what components to use etc that i'm out of my depth with :)
I'm hoping to start a schematic over the weekend on miltisim if i get time. I will upload it to look over so I'm on the right track.
I don't want to use drop-in prototype boards because the space will be so limited I'm confident in making it when I know what it needs and what goes to what.

@djsfantasi I would like to use them as I have them. but you might be right, I'm a little out of my depth on the electrical engineering side so the simpler the better.
It's proving hard to find cobs around the 12v mark on sites like Farell, RS components and digikey the LEDs @Reloadron posted look to long.
I think I read that the minimum voltage my cobs take to power on is 20v if this helps.
I will definitely take you up on the offer of helping with the programming, god knows i need it. I'm In the UK so It might be better if I flash the chip.
Thanks everyone
If you go the ATTiny route, you’ll need a programmer to flash the chips yourself. You can use one that plugs into your computer USB port, like this one. Or you can build your own with an Arduino Uno, like this. in either case, you’d flash the chip using the Arduino IDE. I use the former.
 
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