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how many led's can u use with a 555/556

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ghostman11

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i had a few bits and bobs arrive in the post to get me started on my quest to learn, amongst theese are some 555 and 556 chips.
i thought my first project to get me used to making boards and soldering etc would be a xmas theme for the kids.
they want a flashing snowman :S so i was wondering how many led's i would be able to use on the snowman

many thanks jason
 

Sceadwian

Banned
What specific type of 555/556 do you have? (full chip number)
 

Sceadwian

Banned
lol. And a bright flashlight =O I swear some makers make those inks hard to read on purpose.
 

Vizier87

Active Member
What kind of flashing style do you want? If it's just ON-OFF-ON-OFF to the infinity you can use as many LEDs as you want... The 555 can handle the switching part. Use transistors which power up.. say 10 of them.
See attached.

Use 670 ohms for the resistors, and a monostable operation of the 555 timer.

https://www.electro-tech-online.com/custompdfs/2009/11/LM555.pdf
 

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Sceadwian

Banned
Absolute max rating on the 555 is 16 volts and it's rated at 200ma's. So figure white or blue LED's using a 12 volt supply you could get 3 in series, with 10 strings in parallel, or about 30 LED's per 555 timer (556 is just two 555s on the same chip) that's pretty much at the limit of the 555's output. That would just blink them all on or off though, if you want to have some real fun pick yourself up some shift registers to go with the 555s. Then you can do light chasing and patterns. For just a simple flashing snowman though wouldn't be too bad. If any of this is a bit over your head or you want more details lemmi know I'll flesh it out a bit for ya.
 

Sceadwian

Banned
Vizier the 555 is more than capable of driving a decent number of LEDs without extra transistors, and the voltage is high enough that you can tripple the number of LED's by doing leds in parallel+series, it also wastes a LOT less power as heat.
 

ghostman11

Well-Known Member
thanks for that guy's, could you explain a little more about shift resistors it sounds interesting, patterns of flashing would be good, i have a 12v power supply btw.
all this playing about is so i can learn as much as poss as quick as poss my real goal eventualy is thermostats and diff parts for incubators. at the mo i am spending 6-7 hours a night trying to get my head round basic therory and learning about making boards etc. i do appreciate all the help
 

Sceadwian

Banned
The 555 is a good place to start. shift registers flip flops and other logic gates mix well with them.
Basically you use the 555 to create a clock signal (which can be adjust with a poteniometer) Passing that clock through a flip flop in various ways can give you a clock at 1/2 1/4 1/8 etc.. the main clock speed and a second 555 could be used as a simple inverter (as well as many other things) A serial in parallel out shift register will push whatever bit is on it's data line down the line (usually 8 output) every time the clock line is strobed, so you set it up so that every time the clock line is strobed the data line is fed the alternating bits. So it pushes 01010101 down the register, every time the clock ticks the bits advance one more. Do this with a series of LEDs and you'll get a marque like effect. There are a lot of options. Simply blinking a bank of LED's is a good place to start though.

Figure out what LED's you're going to use and that's where you'd start. You need to know the current rating of the LED's and their forward voltage at that rated current. From there you can determine your power requirements and how many LED's the 555 can light at once.
 
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ghostman11

Well-Known Member
thanks alot guys, right i am off to investigate a bit further and work out what leds we want and how many :D no doubt i will be back later for more help lol
 

ghostman11

Well-Known Member
ok i have ordered some of theese 200, 5mm 3-Pin Dual Bi-Color Red/Green Bright Led,3RG5 on eBay (end time 05-Dec-09 14:42:18 GMT)

also i forgot to mention i have some LM339N Quad Comparators,LM393 Dual Voltage Comparators,4060 14-Stage Ripple Counter and 4017 Decade Counter on order :D i was wondering if i could use any of theese as in the kids snowman (ok it's my snowman realy i fess up), i have spent hours reading thru different stuff on the forum and i have picked up so many good bits of info and idea's, i have to say that this is deff one the best electronics forums out there and not many are as helpful and friendly
 
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audioguru

Well-Known Member
Most Helpful Member
The cheap Chinese LEDs have no datasheet and appear to have a very narrow angle. If they do not point directly at you then you won't see them.
 

ghostman11

Well-Known Member
thats a pain!! just ordered them, oh well never mind i will have a play with them see what happens. thanks for the info i will bear that in mind for next time ;), i should have known u get what you pay for
 

Vizier87

Active Member
Vizier the 555 is more than capable of driving a decent number of LEDs without extra transistors, and the voltage is high enough that you can tripple the number of LED's by doing leds in parallel+series, it also wastes a LOT less power as heat.

Well that depends on how much LEDs he's using, eh? How much are you using Ghostman?
 
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