How to connect several leds into a ic 555

[Johanx2]

Hi guys, I have planned to make a simple flashing led matrix (Maybe 50x50) so I can use it as an amazing bike rear light attached to my backpack.

How can I connect 10, 20 or even 50 leds to pin 3 ? Is it simple ? or will I need a lot of extra components ? (like transistors) Thanks so much.


**broken link removed**

 

[tpetar]

You can see this examples:







You should use transistor at IC output pin to handle current. How much led can be used depends from battery capacity and voltage, and of course from led forward voltage and led current for full brightnest.

 

[Johanx2]

:-| I am not looking for this! I don't want to flash "two different groups" of leds, I just want to turn on and off all the leds, at same time. Thanks anyway.

 

[tpetar]

Then disable or dont use one branch of transistor with leds. Its so simple. ;-)

 

[Johanx2]

But tell me, should I also remove the transistor and the 10k resistor ? how many mw does the transistor drive ? I have been told that pin 3 of IC 555 can drive about 200mw.

:smile: Can I replace that simple transistor instead of a power transistor (like tip31) in order to output more current than the pin 3 ? so I can power more leds.

 

[tpetar]

Use transistor with appropriate resistor. You can check datasheets.

Transistor power depends from how many leds you whant to use and what leds.

Dont forget amount of energy in 9V battery. This battery is for 22mA continuous draining with capacity 400mAh.

 

[IanP]

555 can drive (sink or source) roughly 100mA by itself. You have only 5 branches of LEDs (say, 20mA x 5), and that can be driven directly from pin [3] of 555 without external transistor ..
:wink:
IanP

 

[Johanx2]

Dont forget amount of energy in 9V battery. This battery is for 22mA continuous draining with capacity 400mAh.

That's not a problem since I will feed the circuit with the proper rechargeable battery.

555 can drive (sink or source) roughly 100mA by itself. You have only 5 branches of LEDs (say, 20mA x 5), and that can be driven directly from pin [3] of 555 without external transistor ..
:wink:
IanP

I want to build a big matrix, so I will need to flash at least 40 leds. Please could you recommend me something ? I don't have the knowledge to design circuits (even simple circuits like this). I don't want to flash the matrix with a relay and a 555 :-D it's good idea, but the power consumption of a relay is not funny.

 

[BradtheRad]

You can obtain a bag of 100 led's for a few dollars mail order.

A 555 IC (purchase 2 or more) should still cost under a dollar mail order.

You'll probably use perfboard to mount everything. It doesn't bend. It has a grid of tiny holes drilled every 1/10 inch. Dimensions: several inches on a side. Cost several dollars. Tan perfboard is most common.

Whether to use an enclosure is up to you. It will have to be drilled or cut so the led's can poke through.

Say you have 40 led's. You can make 20 strings of 2 per string (with 20 safety resistors). That way the battery voltage can drop to 4 or 5 volts, and the led's will all continue to light.

Experiment by placing the led's on the board, to find a suitable arrangement that looks good from close and from far away. Do this before you begin soldering, for obvious reasons.

Leave room for the driving circuit. Consider installing an on-off switch. You must determine which side is best to install components, whether on the led bulb side, or the led wiring side. Any tall components may interfere with the enclosure on the led bulb side.

I would secure the battery leads to the perfboard by tying them down with short lengths of wire, or by coating glue over a half-inch worth of each wire. Hot melt glue. This will take stress off solder connections and adjoining bare wires.

 

[Johanx2]

Thanks brothers. At the end I am going to build the next circuit:

**broken link removed**

It supports 40 leds for each group, I am going to eliminate one group and just connect the number of leds I want (up to 40).

 

[trsctln]

Dear friends,

I am new to here and new to electronics. I want to light up 80 white red led’s from this circuit. Please tell me how I can do it

Thank you,

 

[BradtheRad]

I want to light up 80 white red led’s from this circuit. Please tell me how I can do it

White led's operate on a different voltage than red, unless you obtained batches whose specs match each other.

In simple terms you will start by stringing together led's, till their total operating voltage is not higher your power supply. (The schematic in the previous post has two led's per string. You may end up with a different number.)

Then you'll add a safety resistor which limits current through the led string to a safe amount (often 20 mA).

You'll make up as many similar strings as needed, until the total is your desired number of led's.

 

[trsctln]

Dear friend,

Thanks for your help, and also I like to know this. What is best transistor for light up 80 leds C1061 or D313.

I am using 12V supply and if LED voltage is 3V, is it possible to add 80 LED‘s like this.

4 LED’s in series x 40 parallel sets

Thank you,

 

[BradtheRad]

Dear friend,

Thanks for your help, and also I like to know this. What is best transistor for light up 80 leds C1061 or D313.

The transistor probably can be a general-purpose medium-power. TO-220 package.

The more led strings you have, the greater the current through the transistor. If you have 30 of them, that's 30 x 20 mA, or 600 mA. The transistor must be able to conduct 600 mA. At the same time there may be some voltage drop across the transistor. If it is 2V, then the transistor must dissipate 2 x 600 mA, or 1.2 W. This is too high for a small TO-92 package.

Hence a larger size is probably needed. And chances are you will not need a hefty TO-3 transistor.

I am using 12V supply and if LED voltage is 3V, is it possible to add 80 LED‘s like this.

4 LED’s in series x 40 parallel sets

Thank you,

Is the supply constantly 12.0 V? You may get by with 4 led's per string in that case.

Only by testing can you know for sure. If the led's do not light, then you have added too many led's.

There is a need for caution. If the supply V rises or falls slightly, it causes a drastic change in current through led's. This is the reason for a safety resistor inline with every string, to limit current. (However there may be led modules made for certain supply voltages, and are self-regulating, etc.)