2 flashing led circuit

[captaincaveman]

help, hi guys looking for a circuit that will alternate two led's and be controllable to set the flash rate, also to be able to be switched with a ldr or equivalent. Also to run off one or two(paralleled) pp3 batterys.

How long would a circuit be able to last of two pp3's in parallel? looking for as long as possible


what i'm trying to do is set up a dummy alarm box, got the box, which is slim line with a blue plastic bottom for strobe, but normal mains alarms have two alternate led's flashing when in operation

any help would be appreciated

 

[HarveyH42]

Try discovercircuits.com, they have tons of LED circuits. But if you want a very simple, very long lasting solution. Use a single flashing LED, and 2 batteries. The fewer components, the lower your power needs. The Flashing LED runs direct off the battery, no resistor required. Believe they are in the 2-3 Volt range, regardless of color, and flash at 2 hz... This is only the cheap and simple solution for a deterent.

Now, if your goal is to make a simulation of the actual alarm, so somebody else thinks they are protected, when actually they no longer are... hope you get caught.

 

[captaincaveman]

Try discovercircuits.com, they have tons of LED circuits. But if you want a very simple, very long lasting solution. Use a single flashing LED, and 2 batteries. The fewer components, the lower your power needs. The Flashing LED runs direct off the battery, no resistor required. Believe they are in the 2-3 Volt range, regardless of color, and flash at 2 hz... This is only the cheap and simple solution for a deterent.

Now, if your goal is to make a simulation of the actual alarm, so somebody else thinks they are protected, when actually they no longer are... hope you get caught.

no its for myself, had a lot of break ins in the area and cant afford an alarm yet. so better to look like i've got one till i can afford one. put up good locks and pir 300watt spot but need to look like i got alarm cause my house is the only one in about 20 houses that hasn't, so who they gonna pick on. ME

just all the houses ive seen all have two flashing lights. i come from a family of police officers, so don't know what your implying

 

[Hero999]

Use this **broken link removed** with an **broken link removed**.

 

[captaincaveman]

Use this **broken link removed** with an **broken link removed**.

i got that same astable vibrator circuit(found a couple minutes ago, same site ), just not sure what part of the light sensor to use, i dont need the relay and i assume the 4001 diode, but what else dont i need and where/how do i put them together and its gotta run of pp3 9volt batterys

 

[Hero999]

That's right, omit the relay and diode and replace them with the astable multivibrator (connect both +V's together and the flasher's 0V to Q1's collector).

They're both are designed to run 9V as shown in the shematics, right?

So of course they will run from your pp3 batteries.

Just another thought, to increase stability connect a 1M resistor from pin 3 to pin 6 on U1 on the dark detector circuit, as it will introduce some hysteresis into the circuit.

 

[HackinBlack]

flashing LED's are available with built-in resistors,as mentioned;they're used for dummy alarms in cars,the next easiest would be to use one of the micropower flasher IC's developed to light up fire escapes in buildings,these use very little power so battery use is fine.On the subject of battery use;using batteries in parallel is not such a good idea,as although you double the capacty,in practice one will drain more quickly than the other;meaning one will 'carry' the other and fail sooner!any good quality PP3 should last for six months plus if all it does is flash a pair of led's as remember its the 'overall' consumption that counts the actual on time is very low indeed... Failing that buy a dog,burglars are cowardly scum who hate to be shredded!

 

[audioguru]

The multivibrator circuit causes the LEDs to alternate, so the battery has a constant load current of about 22mA when the battery is new then dropping as the battery runs down.

Two little PP3 9V alkaline batteries in parallel have hardly any capacity, so the LEDs will get dimmer and dimmer lasting for about only 60 hours.
A very expensive way to waste batteries.

If the multivibrator blinked each LED briefly, it would still be very noticeable, then the average battery current would be very low and a single little PP3 9V alkaline battery will last for a very long time.

 

[AllVol]

Just for a simple set-up that might keep the bad guys away, you could use a 555 timer, with one LED between V+ and pin 3, the other between pin 3 and ground. A simple LDR divider circuit could turn it on.

Just an idea.

AllVol

 

[captaincaveman]

Just for a simple set-up that might keep the bad guys away, you could use a 555 timer, with one LED between V+ and pin 3, the other between pin 3 and ground. A simple LDR divider circuit could turn it on.

Just an idea.

AllVol

have you a scematic for that? i thought it'd be easy to flash two leds at night only, 6 months outa a battery would be fine. i was going to look at fitting a solar panel to charge batterys, just like you get in stand alone garden lights but the case is very flat and a solar panel on the front might not make it look authentic

using the flashing led's is there a way of getting them to alternate, then adding ldr, would that increase battery life? or are there other battery's that would be better, say bank of 6 or 8 AA's or is there similar problem?

 

[audioguru]

A 555 oscillator wastes its supply current of 5mA from a 9V supply. A Cmos oscillator would have an extremely low supply current.

A 9V battery wastes 7V when it powers 2V red LEDs. A lower battery voltage would waste less.

Four AA alkaline battery cells in series are 6V, cost about the same as a little PP3 9V alkaline battery and has 5 times the capacity (lasts 5 times longer).
A 6V battery will drop to 4V as it runs down and 2V LEDs will still be pretty bright. Even blue 3.3V LEDs could be used.

Cmos oscillators could briefly blink each LED brightly and alternate, and the battery will last for a long time.

 

[captaincaveman]

A 555 oscillator wastes its supply current of 5mA from a 9V supply. A Cmos oscillator would have an extremely low supply current.

A 9V battery wastes 7V when it powers 2V red LEDs. A lower battery voltage would waste less.

Four AA alkaline battery cells in series are 6V, cost about the same as a little PP3 9V alkaline battery and has 5 times the capacity (lasts 5 times longer).
A 6V battery will drop to 4V as it runs down and 2V LEDs will still be pretty bright. Even blue 3.3V LEDs could be used.

Cmos oscillators could briefly blink each LED brightly and alternate, and the battery will last for a long time.

thanks, how would i do that,with the cmos? failing that i'll have to look and see how many alarms run just one led, the could get a flashing one, then its just a matter of ldr control, that should also run along time i assume. or if that drains more. how long would a flashing led last if i ran it 24/7 and what would be the best batteries/set up for maximum running time?

Sorry, im asking loads of questions

 

[Hero999]

I would use a CMOS astable run the circuit off 3V, hte output stage would consist of two LEDs connected in series with no current limiting resistors, pin 3 of the 555 would be connected in between the two LEDs via a failry small electrolytic capacitor (10uf - 100uF).

If you want to stick with the circuit I posted previously then you might want to consider using a DC mains adaptor, or solar power (which I know you've already consigering).

 

[audioguru]

I have Ultra-bright Chaser projects that have batteries that last a long time.
The bright red chaser uses two AA cells. The bright blue and bright green chasers use four AA cells for the higher voltage.
The Cmos ICs used are 74HCxx that have a very high output current (for Cmos) and have a minimum supply voltage of 2.0V.

Ordinary 555 ICs have a minimum supply voltage of 4.5V. Then its output voltage would be only 3.3V, enough for a single LED.

 

[captaincaveman]

thanks guys, bit overwhealmed on what to do, its the power problem more than anything. theres cheap solar charger panels(says for personal stereos, mp3 players etc) says output approx 3vdc at up to 80ma. would a couple of these do? could they be put in parallel? and would nicd aa recharge batterys be used? think they are 1,050mAh, how would they be set up?

 

[HarveyH42]

For $3-5.00 you can pick up a solar garden light (Dollar Store, BigLots... free from the neighbors yard), seen just the guts in several online surplus stores around $4.00. Anyway, just remove the guts, replace the LED with a flasher, install in your case. Should last all night, simple, quick and easy.

 

[captaincaveman]

For $3-5.00 you can pick up a solar garden light (Dollar Store, BigLots... free from the neighbors yard), seen just the guts in several online surplus stores around $4.00. Anyway, just remove the guts, replace the LED with a flasher, install in your case. Should last all night, simple, quick and easy.

Looked round neighbourhood and some were twin flashers, some single and some didn't flash at all, so mine single led won't look outta place. got solar garden light for £3 new with better solar panel(not sure on spec but you can see quality in it compared to some), got it all working and in case, gonna install it tomorrow, take some pics(try at catch it when flashing)

had to box off led, cause when it flashed you saw all the insides which didn't look good, so encased it so box stays white and led flashes just blue centre bit

thanks again guys

 

[Hero999]

Just rip out the LED and connect the dual LED flasher in its place.

 

[captaincaveman]

Just rip out the LED and connect the dual LED flasher in its place.

Will the solar panel be able to keep feeding it?, remember im using uk light

 

[Hero999]

It will proabably take less power than the origional LED.