# Boosting current on a circuit?



## Revenant

I wanted to use multiple LEDs on a flicker circuit (or at least substitute high-intensity ones which are about 30 mA) but didn't know if it could handle the juice. I emailed the distributors of the ICs and they responded:

_*10 to 20mA output current. Therefore it can drive one LED only. If you need add more on the circuit, you must add a transistor to boost up current.
*_

Okay, transistor. Now, what kind and how do I add it to the circuit to boost the capacity? The ICs have 3 leads; Pos, Neg, and a third I'll call L-. the battery attaches to Pos and Neg (duh) and the LED hooks up to Pos and L-.










So, all you high-tech whizbangers out there... couldja help a poor Luddite out? I think a fire-flickering LED spot could come in SOOOOO handy....!


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## heresjohnny

Hey Rev, I think this will work. I use something like this to drive LEDs of a low power op-amp. This should be good for up to 100mA. You can use a 2N2222 also for the transistor, that will get you up to about 500 mA. I think I have the leads right, hope it works!


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## heresjohnny

I think I need to clarify a little.

Get a transistor, (I have used a 2N3904 and a 2N2222) and look at the package to see which lead is the Emittor (E), the Base (B) and the Collector (C). 

Carefully solder the Base of the transistor to L- lead of your thing. Solder the Emitter of the transistor and the negative lead of your battery to the (-) lead of your thing. Twist together and solder the Collector of the transistor to one side of a 470 ohm resister. Solder the Emitter of the transistor to cathode of the LED (the side of the LED with the flat edge and the shorter lead) to the other side of the 470 ohm resistor. Solder the Anode of the LED (longer lead) and the positive battery lead to the (+) on your thing.

If you want, PM me, and I can send you my address. You can ship some to me and I can wire em up for you and take pictures!


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## Revenant

Thank you johnny! Especially for the second post -- handing me a schematic is like handing a CD to a deaf person; I need electronic instructions to be pretty explicit lol

When my LED's I'm bidding on come in I'll try to wire up an LED spotlight to one of these ICs and see what happens. I think having a mini-spot that throws firelight could be mighty useful. And a JOL would show up much better if several LEDs were flickering inside at the same time. This may be a bit ambitions for someone like me who knows Jack Shi(r)t about electronics but I guess I gotta learn somehow lol


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## heresjohnny

Revenant said:


> Thank you johnny! Especially for the second post -- handing me a schematic is like handing a CD to a deaf person; I need electronic instructions to be pretty explicit lol
> 
> When my LED's I'm bidding on come in I'll try to wire up an LED spotlight to one of these ICs and see what happens. I think having a mini-spot that throws firelight could be mighty useful. And a JOL would show up much better if several LEDs were flickering inside at the same time. This may be a bit ambitions for someone like me who knows Jack Shi(r)t about electronics but I guess I gotta learn somehow lol


The 470 ohm resistor takes the place of the resistor that you usually put in an LED spotlight. Also, I have used hot glue on the tip of the ultrabright LEDs to act as a diffuser, and I have read somewhere (in HauntForum I think) about using clear silicon to do the same thing.


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## gmacted

Revenant,

What are you using for source voltage?

Depending on your source voltage and the circuit, you may be able to put a couple of 20 mA LEDs in series with this circuit. LEDs in series will draw no more current, but the forward voltage drop will be the limiting factor.

Do you have the specs for the high intensity LEDs you wnat to use? The important specs are the forward voltage and the forward current.

Heresjohnny's circuit will work fine, but you will want to customize it for the number of LEDs you want to use.

Are you running these circuits using wallwarts? If not, how you configure the circuit will save battery life and allow you to run the circuit for a longer period of time using a battery.

This may be a little confusing, but I'm just trying to help (really).


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## Revenant

The specs on the LEDs are thus:

* Emitted Colour : White
* Size (mm) : 5mm
* Lens Colour : Water Clear
* Peak Wave Length (nm) : N/A
* Forward Voltage (V) : 3.2 ~ 3.8
* Reverse Current (uA) : <=30
* Luminous Intensity Typ Iv (mcd) : Average in 13000
* Life Rating : 100,000 Hours
* Viewing Angle : 20 ~ 25 Degree
* Absolute Maximum Ratings (Ta=25°C)
* Max Power Dissipation : 80mw
* Max Continuous Forward Current : 30mA
* Max Peak Forward Current : 75mA
* Reverse Voltage : 5~6V
* Lead Soldering Temperature : 240°C (<5Sec)
* Operating Temperature Range : -25°C ~ +85°C
* Preservative Temperature Range : -30°C ~ +100°C

As you can see even one of these guys would probably send the poor IC to Silicon Heaven. Johnny said the 2N2222 transistor would support up to around 500 mA so that's what I'd need to drive one of his 7-lamp spots. 

As for power supply, I don't know yet. He made his steady spots to run off a 9V battery, which would be cool, but the IC can only handle about 4.5V so I'm sure 9V would let the blue smoke out. The optimum voltage for the LEDs is around 3.5 anyway. I'd either need a rather beefy spotlight body that could handle 3 batteries or can I step down the voltage of the 9V with something small enough to fit in the little PVC tube? Otherwise I'm pretty much stuck with running a line to a DC power supply. 

I think the thing that's cool about battery powered spots is they'd be better for outdoor use; no extra wires to route and trip over or power supplies to weatherproof. And at night you can just collect them and bring them inside without disconnecting anything.


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## heresjohnny

What spotlights are you using? How is the array configured? Driving a 7 led spot is different than a single LED (what I thought you were doing). Gmacted is right about tuning the circuit.


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## Revenant

Well, the spotlights I had in mind were the ones on your http://www.johnnyspage.com/ledspothowto.htm page. Although you show the actual making of a 5-lamp spot using parallel arrays of 2, 1, and 2 lamps, you also had a great pic of lighting from a 7-lamp spot using the same size LED's I'm getting. I think the stronger light would be good for a firelight source.

Using linear's calculator, the only circuit I can use if I use a 4.5V power supply is a completely parallel circuit, 7 branches each with its own resistor. If I used a 9V supply it could give me a 4-branch series/parallel circuit that would not only save on components but draw less current (120mA instead of 210 for the completely parallel one). But 9V would smoke the IC so that's out. Using the series/parallel configuration I'd have to use a separate flicker IC for each branch and that won't do because all the lights have to be in synch.

So... I guess I'd have to power it with 3 regular batteries (I guess I could use AA's and put them in a flat base). An alkaline AA battery averages 2700 mAh so with a drain of 210 mA I guess that's about 12 hours of use... if it were a steady spot. But technically it should be less drain because the IC is ramping the intensity of the LEDs up and down so they're not full-on the whole time, so they should last longer than that. Dunno. Whatcha think?

And... since you thought I was just using a single Hi-brite LED at first, you put that 470-ohm resistor in that circuit you drew. Do the resistors in each branch of the circuit from linear's calculator take the place of that? So I just connect the collector of the transistor to the cathode node of the LED array?


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## gmacted

The small circuit is most likely a 5V circuit, but will operate at 4.5V (three 1.5V batteries in series). You could use a 9V battery and a LM7805 (5V regulator). The output of the regulator (5V) would be used to power the circuit and the 9V would be used to power the transistor/LED portion. A 2N2222 transistor can handle 800 mA (maximum collector currrent). You could easily operate 25 high intensity LEDs using this transistor. The only problem here is the more LEDs you use, the more current you will draw and the shorter the time the circuit will operate. An alkaline battery can source ~580 mA hours. If your circuit is drawing 100 mA, the battery will last ~ 580Ah/100mA = 5.8 hours. If you draw 200 mA, the circuit will only operate ~2.9 hours. These values are only approximate and will most likely last longer, but it gives you a ballpark figure of how long the circuit will last.

I built a flicker circuit with three high intensity green LEDs that operates on a 9V battery. I got the circuit to run almost two days using one 9V battery.

You need to make some decisions before you can move forward.


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## Zombie-F

I have this circuit and have tested the voltage at the point hat the LED needs to be inserted, and it only supplies 2.1V, which isn't enough for some LEDs to operate (UV for instance, needs about 3.2V to operate).


gmacted said:


> Revenant,
> 
> What are you using for source voltage?
> 
> Depending on your source voltage and the circuit, you may be able to put a couple of 20 mA LEDs in series with this circuit. LEDs in series will draw no more current, but the forward voltage drop will be the limiting factor.
> 
> Do you have the specs for the high intensity LEDs you wnat to use? The important specs are the forward voltage and the forward current.
> 
> Heresjohnny's circuit will work fine, but you will want to customize it for the number of LEDs you want to use.
> 
> Are you running these circuits using wallwarts? If not, how you configure the circuit will save battery life and allow you to run the circuit for a longer period of time using a battery.
> 
> This may be a little confusing, but I'm just trying to help (really).


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## heresjohnny

The 470 ohm resistor is just a ballpark value from another circuit I have messed around with that drives an LED with the output from an op-amp comparator.

I think the voltage regulator would work also, but I don't know off the top of my head what the supporting components would be. If no one else posts a circuit I can take a stab at it.


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## Revenant

The stats on the IC state optimum function at voltages from 2.6 to 4.5 V. The alkaline battery stats I'm finding online are way different from the ones you're going by. You're saying only about 580mAh; the stats I'm looking at are giving values of 700 or lower only under high loads of 1000mA or so. Under low loads I'm seeing values well over 2000. I get more than 3 hours playing time out of my CD player and I'm certain it's pulling more juice than 200 mA to operate a laser diode, motor, and speakers. Maybe not but it seems to me.

But whatever. So they only last one night. Batteries come in bulk packs at the dollar store and I can always splice a bypass jack to plug in a wallwart. At any rate, what are these decisions I need to make?


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## gmacted

Revenant said:


> The stats on the IC state optimum function at voltages from 2.6 to 4.5 V. The alkaline battery stats I'm finding online are way different from the ones you're going by. You're saying only about 580mAh; the stats I'm looking at are giving values of 700 or lower only under high loads of 1000mA or so. Under low loads I'm seeing values well over 2000. I get more than 3 hours playing time out of my CD player and I'm certain it's pulling more juice than 200 mA to operate a laser diode, motor, and speakers. Maybe not but it seems to me.
> 
> But whatever. So they only last one night. Batteries come in bulk packs at the dollar store and I can always splice a bypass jack to plug in a wallwart. At any rate, what are these decisions I need to make?


Here are the ratings for Duracell 9V batteries:

Duracell 9 Volt Alkaline Battery (Package of 2)
The popular copper-top battery / Long-life Power 580 MAH / For CD and Cassette Players

You need to decide how many LEDs you want in the circuit and if you want to use a single 9V battery or 3 AA batteries. Once you decide that I can make a circuit for you that will minimize the number components and minimize the current draw to get the longest life out of the circuit.


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## gmacted

heresjohnny said:


> The 470 ohm resistor is just a ballpark value from another circuit I have messed around with that drives an LED with the output from an op-amp comparator.
> 
> I think the voltage regulator would work also, but I don't know off the top of my head what the supporting components would be. If no one else posts a circuit I can take a stab at it.


The 7805 only requires a single electrolytic capacitor on its output for supporting components and even that may not really be required in this case. It's used to keep the voltage up during the initial power-up/current draw.


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## gmacted

Zombie-F said:


> I have this circuit and have tested the voltage at the point hat the LED needs to be inserted, and it only supplies 2.1V, which isn't enough for some LEDs to operate (UV for instance, needs about 3.2V to operate).


Zombie-F,

I know you wanted to use this circuit in your lanterns. What are you going to use for a battery source? Three AA batteries? I'm assuming you are only going to use one LED. Is that right? You could use a transistor or a FET so you can use a high intensity LED. Let me know if you want or need any help.


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## Zombie-F

gmacted said:


> Zombie-F,
> 
> I know you wanted to use this circuit in your lanterns. What are you going to use for a battery source? Three AA batteries? I'm assuming you are only going to use one LED. Is that right? You could use a transistor or a FET so you can use a high intensity LED. Let me know if you want or need any help.


Thanks, but I already have a workaround all figured out. My cousin and I have a schematic worked out and I just have to build one and make sure it works. It does use a transistor to get around the limited voltage pumped out by the chip.

I may try AAA batteries since they're smaller. I just really have to compare the cost of the two to see which would be the most cost-effective.


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## heresjohnny

Zombie-F said:


> Thanks, but I already have a workaround all figured out. My cousin and I have a schematic worked out and I just have to build one and make sure it works. It does use a transistor to get around the limited voltage pumped out by the chip.
> 
> I may try AAA batteries since they're smaller. I just really have to compare the cost of the two to see which would be the most cost-effective.


Can you post the circuit? Me like circuits!


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## Revenant

gmacted said:


> Here are the ratings for Duracell 9V batteries:
> 
> Duracell 9 Volt Alkaline Battery (Package of 2)
> The popular copper-top battery / Long-life Power 580 MAH / For CD and Cassette Players
> 
> You need to decide how many LEDs you want in the circuit and if you want to use a single 9V battery or 3 AA batteries. Once you decide that I can make a circuit for you that will minimize the number components and minimize the current draw to get the longest life out of the circuit.


I want to use AAs; the wimpy stats you gave (580mAh) are indeed for a 9V, since a 9V is actually a box with six wussy little AAAA battery fetuses inside that parallel up to give good voltage but have very little current-producing paste in them. It's like having 6 pissed off 2-year-olds; the aggression and ferocity may be there but no real muscle. AAAs would have better than 5 times the capacity of that.

As far as what I want, like I said, for the spotlights I'd like to go with 7 LEDs of the type I described. I guess they could be ramped down to 5 but 7 would be awesome. For the time being (meaning the prop contest) I'm good with flickering a single 13000mcd LED (much easier) but the eventual goal is for a synchronized fire spotlight.

ZF; you got your flickerers from apmall on ebay? I'm surprised you say you only got 2.1V from it. It says optimum 2.6 to 4.5 in their description. Did you test several or just one? Maybe they don't have good quality control and the ICs differ from each other? Theyre cheap enough to play with I suppose and I can afford to smoke a few but I hate to think they're unreliable.

Anyhoo johnny, gmac, ZF thanks for the input... I think this concept is possible it just may take a few tries. I'll work on the circuits I found and we'll see if we can cobble this together.


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## gmacted

Revenant said:


> I want to use AAs; the wimpy stats you gave (580mAh) are indeed for a 9V, since a 9V is actually a box with six wussy little AAAA battery fetuses inside that parallel up to give good voltage but have very little current-producing paste in them. It's like having 6 pissed off 2-year-olds; the aggression and ferocity may be there but no real muscle. AAAs would have better than 5 times the capacity of that.
> 
> As far as what I want, like I said, for the spotlights I'd like to go with 7 LEDs of the type I described. I guess they could be ramped down to 5 but 7 would be awesome. For the time being (meaning the prop contest) I'm good with flickering a single 13000mcd LED (much easier) but the eventual goal is for a synchronized fire spotlight.
> 
> ZF; you got your flickerers from apmall on ebay? I'm surprised you say you only got 2.1V from it. It says optimum 2.6 to 4.5 in their description. Did you test several or just one? Maybe they don't have good quality control and the ICs differ from each other? Theyre cheap enough to play with I suppose and I can afford to smoke a few but I hate to think they're unreliable.
> 
> Anyhoo johnny, gmac, ZF thanks for the input... I think this concept is possible it just may take a few tries. I'll work on the circuits I found and we'll see if we can cobble this together.


I think that using AA batteries in this case will probably be your best bet. It will take up a little more room than a single 9V battery, but the mAh ratings of the AA batteries is very good (~2800 mAh). Running 7 30 mA LEDs with three AA batteries will last at least 13 hours. They will probably run much longer than that. I would guess for probably at least one day.


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## Revenant

*********Update/Bump*************

Well, no luck with the booster circuit. The one I was given didn't work... I tried correcting it with advice from someone else, and it still didn't work. One guy suggested that the pulsed signal from the IC isnt carrying enough current to turn on the transistor. So the fire-flicker spotlight is still not coming into being.

However... even though the Hong Kong vendor said that the circuit can only handle 20 or 25 mA and that the hi-brite LED would kill it, I've been driving a 30 mA 13,000 mcd LED with it for hours now. Maybe I can at least run individual candles that can actually throw out some real light. Would be handy indoors; they could be the actual primary light source.


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## DeathTouch

Another thing you could try is a relay.


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## The_Caretaker

Whats the output look like, if it is a PWM signal you should be able to use it to control a FET.


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## Sickie Ickie

Or if you plan to use it in outer space, you could use Boba Fett


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## DeathTouch

Sickie Ickie said:


> Or if you plan to use it in outer space, you could use Boba Fett


Oh nice! Your powers are great Old ben, you are our only hope!


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## The_Caretaker

> Quote:
> 
> 
> 
> Originally Posted by Sickie Ickie View Post
> Or if you plan to use it in outer space, you could use Boba Fett
> 
> 
> 
> Oh nice! Your powers are great Old ben, you are our only hope!
Click to expand...

Boy are we in trouble


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## Revenant

The_Caretaker said:


> Whats the output look like, if it is a PWM signal you should be able to use it to control a FET.


Well, I'm assuming it's a PWM signal since simple voltage control wouldn't do LED's like that... so... these FETs of which you speak; how would I use one? and would I need additional components as well to make it work?

Oh btw, I ran my 30 mA LED on that flicker IC for 15 hours yesterday, 13.5 of them in one continuous shot, and it was still flickerin' like a champ when I disconnected it last night with no change at all. I'm not an electronics-head but I'm thinking this is an indication that 30 mA is NOT too much current. If it were damaging to the IC surely I would have at least seen some change in the activity in that time.


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## Dr Morbius

Did your IC get hot? It may have worked, but the excess current may shorten it's life, even though it worked for a day. If it stayed cool, you're probably good to go.


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## The_Caretaker

Run it again, if it isn't to hot to touch then I wouldn't worry about it. But a FET is basically just a high power transistor with fault circuitry. For that matter using a transistor that is capable of the current you are passing would work (got to remember KISS) just hook up the output to the gate of the transistor.


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## Revenant

I tried the transistor idea, it didn't work. Lemme make sure I got it right... the base of the transistor hooks to the output of the chip, the collector connects to the positive power supply and the positive lead (and resistor) of the LED, and the emitter connects to the negative lead of the LED. Izzat right? Cuz it dint do nuthin when I tried it.

And I left the flickerer running overnight for 6 hours and it was cool as a cuke this morning when I turned it off.


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## The_Caretaker

After 6 hours and not hot I wouldn't worry about it, but the setup you describe would work for a PNP if the output from the chip had a large enough voltage since the frequency is probable low. What is the voltage level of the output? What is its frequency?


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## Revenant

Mister meter measured moltage -- eh, voltage -- that spent most of its time ramping up & down between 2 and 3.5 volts with occasional peaks and dips on either side of that range. The tranny's a 2N 4401. Frequency, I don't have a clue. Or a scope. Or a clue about how to use a scope, for that matter.


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## Sickie Ickie

you gargle with it.


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## The_Caretaker

Its a NPN Transistor here is a data sheet http://www.fairchildsemi.com/ds/2N/2N4401.pdf, does you voltmeter measure freq (Hz)? 
If you move the diode to the emitter side it should work.
You really need to scope the output to see max voltage since you are reading an average value with just the volt meter. The gate on this trans needs 6 volts


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## pshort

If you look at the first post in this thread, it appears that the chip is pulling the cathode of the chip to ground to turn the LED on. This means that if you want to add one single transistor to boost the current, it should be a PNP transistor instead of NPN. It should be basically the reverse of heresjohnny's post (with the addition of a base resistor).

I don't have a schematic capture program on this computer, so I'll describe it in words. The transistor should be something like a 2N3906, with the emitter connected to the positive battery voltage and the '+' of the IC. The base should be connected to the control pin of the IC with maybe a 10K resistor, and the collector should go to one end of a current limiting resistor. The other end of this resistor goes to the anode of the LED, and the cathode of the LED goes to a '-' voltage. If a regulator is needed to power things from a 9V battery, use a 79L05 or 7905, depending on the current required.

--

Phil


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## pshort

Oops, sorry about the double signature there, force of habit.


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## Revenant

Aaaah okay... I tried to use the wrong components... d'oh... thank you CT and pshort, that should bump me back onto the true path lol I'll get this little *!&%# goin' yet...


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## Revenant

*SUCCESS!!!!!!!*









That was it pshort!! I made a drive out to my fave 'lectronics shop where a friend of mine works to scrounge up some of them thar 3906's and showed him the wiring diagram I drew off of your description.. he said that's the one... except for the base resistor was way too much, he said go around 1k. I had a bunch of 470-ohm laying around so I used two of those. The whole spotlight flickers like a candle now... I can't wait to try this out in the dark!

*THANK YOU EVERYONE!!!! *I can work a soldering pen pretty well but don't actually know electronics worth squat so I really depend on people's knowledge of this stuff to get circuits going. Couldn't a dunnit widdout 'chas. Now... on to the applications! I need to buy more LED's now.....


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## pshort

I'm glad to hear that it worked out for you.


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## Death Master

Good going Revenant, now you need to draw up a circuit and post it with a how to, so others can enjoy the fruits of you labor. That would be nice.


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## heresjohnny

Hey pshort, if you have a chance could you explain a little about knowing it needed a PNP instead of a NPN, or point us to a web page? Electronics is a hobby for me and I have a lot to learn! 

Hey Rev, please post (or send, or something) a picture of what you ended up with, would love to see it.


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## Revenant

Okiedoke... here is the circuit:










I hope I got all the symbols right LOL schematics are not exactly my strong point...
BTW the resistors attached to the LEDs will vary, of course, depending on your LEDs and chosen power supply. My LEDs are 3.5 volt and I'm using a 4.5V supply, so those resistors are 39 ohm in my lights.

This is not theoretical or something that "should work"... this is the real circuit and it works nicely.


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## Koumajutsu

anyone know a good p-channel FET that would really boost this circuit instead of a lossy transistor?


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## Death Master

Thank you Revenant.


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## pshort

Revenant - the schematic looks good.

Koumajutsu - what's wrong with a good old BJT? They're cheap, rugged and easy to find.

The 2N3906 is good for 200 mA (and you can still use the 1K resistor at these current levels). For higher current output you could use a TIP42, which would be good for up to about 1A (if you decrease the 1K resistor to about 100 Ohms). If you need higher current, use a TIP127, which should be good to about 5A (with a good heatsink). All of these parts should be adequately fast for this use.

heresjohnny - I don't have any good links for you, because I've been doing this sort of thing for so long that I've never looked it up on the internet.

As for needing to use a PNP transistor, the very first photo in this topic showed the LED connected between the positive voltage and the output pin of the chip, which told me that the chip 'sinks' current to light the LED. The goal, then, is to use as few parts as possible to replace the LED in the circuit, so that the chip would 'think' that it was driving an LED but would be driving a 'booster circuit' in its place. The type of transistor that 'turns on' when 'sinking' current through it's base is a PNP transistor (you would source current into the base of a NPN transistor to turn it on), and the rest of the circuit follows from this observation.


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## heresjohnny

Thanks pshort, I'm gonna think about your reply when I have a chance.


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## Revenant

pshort said:


> The 2N3906 is good for 200 mA (and you can still use the 1K resistor at these current levels).


Heya pshort I'm running 7 LEDs off this, and each is 30mA... that means 210mA draw. Will this amount of overage put a stress on any of the components? You say the 3906 is a tough little 'sistor but I'd hate to redline my ICs, they're the heart of the system. The ones I put together function well, 'tho I've not put in a long-term performance evaluation.



pshort said:


> As for needing to use a PNP transistor, the very first photo in this topic showed the LED connected between the positive voltage and the output pin of the chip, which told me that the chip 'sinks' current to light the LED.


So, correct me if I'm wrong, I'm just learning this stuff... the clue for you was the fact that the LED is supposed to go between the Pos of the power supply and the output pin, which of course had to be negative, and thus you knew the chip had to be modulating the negative end of things and thus a PNP. Whereas, if the chip was supposed to wear the LED between the output pin and the Neg of the power supply, then you'd know that the chip is modulating the positive current and you'd want an NPN for that. Did I get it right? I'm new to transistors. So much I need to learn.

_P.S. Hey pretty cool how the pic of the schematic turned out eh? I shot it without a flash and it cam out looking like ink on parchment. If I were any good with photoshop I would have turned that into a scroll hehe_


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## pshort

revenant,

The transistor is a bit overloaded, but I wouldn't worry about it. They build margin into them, and it's only a small overload. The story would be different if you were building 10,000 of them (where a few parts failing would ruin all of your profit), but for one or two units I'd leave it alone.

And the rest of what you wrote is quite right.


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## Koumajutsu

pshort said:


> Koumajutsu - what's wrong with a good old BJT? They're cheap, rugged and easy to find.


Well, I have a bad habbit of working in the range of amps, and not miliamperes. especially when I start dropping 3 and 5 watt LEDs in a circuit :winkvil: I tend to go through a bunch of IRF450s and the like, but I never really checked out their switching speed. i guess i could always go read the datasheet


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## pshort

I've never really played with FETs, so my knowledge of their part numbers is limited.

The simplest FET circuit (i.e. single transistor) in this application would be a logic-level P-Channel MOSFET. I don't know if this exists or is cheap/easy-to-find. Beyond this the circuit would need to be two-stage, either to boost the FET drive voltage (using a regular P-channel part) or to invert it (to use an N-channel part).


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## Revenant

Oh, in case anyone didn't catch the post in the Secret Reaper thread, I made a set of these Fire Spots for Pyro (apropos, hmm?  ). If you have any questions about their functionality in lighting, ask him because he's played with them a little bit and now has more experience actually using them than I do LOL

For maximum versatility (I don't know what colors he likes to use in his haunt) I used white LEDs and interchangeable colored gels to give different color combos. This is technically not the best way to do colored LED light: gel coloring is a subtractive process, only allowing one color from the light source to pass through, so your light intensity drops. With incandescent lighting, it's not so bad because you have a really wide mix of wavelengths in your light. But LEDs have pretty narrow wavebands and some colors (red for example) are so poorly represented in the mix that it ends up being pretty dim. A better solution would be to make interchangeable light-heads of each color LED you want, so you get colored light at full strength. This however is the more expensive solution and we had a low price cap on the gift exchange (it also massively increases the amount of soldering you end up having to do lol)

I've already posted the circuit itself; I'll get to work on the how-to soon. I didn't do it earlier because I wanted to maintain some surprise with the gift.

Thanks again everyone for their input, especially heresjohnny and pshort. I couldn't have done it without you guys; technically all I did was come up with the idea and you guys did all the electronics design. I'm proud of this little device because I'm damned near Luddite in my electronics "skills" and this simple little toy is a major breakthrough for my level. This project represents why I love this board so much.


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## Devils Chariot

Klaatu. .. Verada. .. Necktie?...Nectar?...Nickel_!

I resurrect this thread in search of how-tos or at a least parts list!
_


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## TommaHawk

Any major rework needed if I wanted to run this thing using 6v incandescent bulb(s)? Thought I'd power it from a Lemax 3v adapter (those plugins for Spooky Town villages). Obviously this would eliminate the resistors for the LEDs...


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## corey872

Well, a couple problems might arise - the 3904/3906 transistors mentioned are usually only good up to a couple hundred milliamps, so if your 6V bulb is any greater than (6V x 0.2A) = 1.2 watts, it will burn up the transistor. Second, your 3V power supply is going to be pretty low power to drive a 6V bulb - expect the bulb to be pretty dim. Third, LED's are pretty much 'instant on, instant off' so the follow the flicker circuit output very closely. Incandescent bulbs take a small, but noticeable time to heat up and cool down. So the flicker effect will be very muted - the bulb won't get as bright or dim as a comparable LED.

All together, LED's will produce much more flicker with less power and much brighter output.


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## ScaryTinker

*Looking for source of the IC*

Anybody have a current source of this flicker circuit board. I found them on Ebay a couple of years ago but can't find a source now.

Thanks


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## corey872

I haven't seen them around for quite a while. Seemed like they might have been an overstock or closeout as I can't really see a company manufacturing them specifically for the hobby market. So they might be gone for good.

On the flip side, when I bought mine off ebay, I think the guy was asking about $1 each plus shipping. If you go to a dollar store or search around, you can usually find tea light candles for 50 cents each - which will give you the same circuit, plus battery and on-off switch. So actually a much better deal.

We've discussed how to 'hack' both types of tea light candles to make the output drive almost anything...

Normal 'Type 1' candles with separate circuit
http://www.hauntforum.com/showthread.php?t=16052

"Type 2" candles with circuit in the LED
http://www.hauntforum.com/showthread.php?t=16052&page=5


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## Otaku

I made this circuit for using the output of a tea light to drive a higher amperage LED array. Since the flicker portion of the circuit is only driving the transistor, you can run higher amp loads - up to 3A if using the 1IR510 MOSFET.


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## TommaHawk

Dredging this up from a decade ago! I've had this thread saved since way back then in case, someday...

So I've still got a number of these little green flicker circuits. They'll power an LED between 2.5V and 4.5V, outputting only 10-20mA. I'd now like to use this to power a 3V incandescent grain-of-wheat bulb which draws ~57mA. 

Can we review the "what & how" I'd possibly do this? I think the jist was to have the flicker chip drive a transistor assembly instead of a bulb directly, which could feed more amps to the light(s). I'm not hard & fast married to these green circuits, but their size & power draw works perfect for my application. Maybe there's been advances in technology that would make this setup wildly simple, I can't quite follow the diagrams included herein... 

Revenant got this working back then, possibly we could come up with a remedial diagram of the parts and wiring/soldering? 

Thanks so much!


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## corey872

lol - I think you do win the award for oldest resurrected zombie thread! But I'll see if I can help!

You mention 'advances in technology' - yes, you can pretty much buy 'flicker LEDs' in any color of the rainbow now. Just give the LED 3 volts and it flickers. If you are specifically trying to mimic a grain of wheat bulb, you might consider a 3mm warm white flicker LED - that would most likely be the closest in both size and color.

https://shop.evilmadscientist.com/productsmenu/partsmenu/575

If you want to run the green flicker circuit, then you might try just hooking it up to the bulb as you would an LED. It sounds like the volts and current of the bulb is at least a 'ballpark' match for an LED, so it is likely it will run too. ...subject to all the caveats of incandescent bulbs... higher power consumption, slower response, so likely a muted flicker effect, stress on the bulb from constant flickering likely = shorter bulb life, etc.

If for some reason the green circuit doesn't power the bulb satisfactorily, then you'd likely need the circuit I show here (in stunning 240p resolution - but, hey, it was 10 years ago - just be happy it was in color!)






Hope this helps.


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## TommaHawk

Thanks corey872! Maybe you're right... a flickering LED is a much easier way to go. Thanks for the link, too. 

Maybe I'm trying to force the issue adapting this little flicker chip to an incandescent bulb. I've not been satisfied with the kelvin rating of so many "warm white" LEDs. Even though that madscientist site doesn't show the actual warm white one, I'll likely try them.

Your stunning resolution video is... stunning. Is that driving incandescent bulbs? Can you tell me more about what it is (thinking back from 10 years ago)? I think my 3V bulb drawing 57mA is too much for this green chip alone.

Thanks


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## corey872

lol - well, I'd be lying to say I have not been on a quest across the decades for a good color matched flicker LED, too! Hate to count the bins of LEDs I have which failed to generate the color I wanted.

The earliest flicker LEDs were 'yellow' as seen in the video, so in order to drive anything else, we used the small transistor shown. In the video, it's driving two "150mA" warm white LEDs. I happened into a batch of 25 which made a fairly nice warm white, went back to the same seller for more of the exact same thing and they came out looking like snow! ...probably 4500-5000K

In the past few years a rainbow of flicker LEDs - literaly red, orange, yellow, green, blue and violet flicker LEDs are all available. Warm white and cool white flickers have made a more recent appearance though quality and color still seem to be a bit hit and miss. I have 'warm white' LEDs that are too green, 'warm whites' that are too yellow, 'warm whites' that look like snow!

Here is one of the more notable failures:






If you really want to 'nail' the color temperature, you might have to go to a 'real' electronics outlet... digikey, newark, etc and order a specified color temperature - that would likely get you pretty dang close - then you could still drive that LED with what ever you want through a transistor.

I think you green disk would drive the wheat bulb. I made several of these from when those disks came out. Each green disk drives a 150mA warm white LED. I throw one of these in the bottom of a pumpkin, skull or other decor I want a flicker in.

Just be prepared that the wheat bulb will likely show a muted response to the flicker - it takes a lot longer to warm the filament up / cool it off than to switch a solid state diode on/off. That may be desirable or not.


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## TommaHawk

This is great! Our experiences with LEDs have been much the same. As you mention, I'll look at the "real" outlets too, see if anything turns me on. So to speak. 

I think... I'll stick with an LED like you've done instead of putting much effort into my incandescent. Really like your battery pack units too. Gives me hope!

If the flicker is too much, I could have a second steady-lit LED in there too to mute the flicker somewhat.


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