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How do I power this?

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mihica

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I've got this circuit.
wat.jpg

I'm trying to power it with 3 AG3 button cells, but it won't turn on all at the same time. Maybe I don't supply enough amps? What's the problem?
 
You don't mention the power requirements for all those LEDs. Also it is a poor design using LEDs in parallel without each having a series current limiting resistos. It's a poor design practice and should be avoided. I seriously doubt the button cells are providing the needed current. You have two astable multi-vibrator circuits and I count 10 LEDs. Where did that circuit come from?

Ron
 
Well, I'm sorry for being new to all this. Just bought my first transistor 3 days ago. I don't know about this stuff, so, would you mind clarifying where on the circuit I should use additional resistors and what kind of powr supply I should use?
 
Sure and no problem at all. There is a learning curve to all this stuff and every electrical enthusiast needs to start somewhere. We just had a thread a few days ago using a transistor multivibrator to blink some LEDs. Let me see what I can find. Never be sorry for being new to anything. I'll be back with some examples.

Ron
 
Also, read this thread as it shows the basics of what you are trying to do. Note how the original posted circuit needed changes made and what they were.

Ron
 
I just noticed it was your thread. Why are you starting another thread? Did you get the original circuit working. When you start new threads it can confuse those trying to help you in your original thread.

You will need the data sheets or specifications for the LEDs you have so we know the forward voltage and current requirements. Different color LEDs have different forward voltages and currents. Also, keep your LEDs on the collector sides of the transistors, I see above you have them on the emitters. Your first circuit worked I see with the canges?

Ron
 
Hi,
The collector resistors in your two multivibrators are too high. They prevent oscillation. Reduce them from their current value of 100R to 22R or lower. Also, it would be better to have an equal number of LEDs for each of the two emitters of a multivibrator. So, for example, balance the two paralleled orange LEDs with two paralleled yellow ones, for the multivibrator on the LHS and the one on the RHS. That would give you equal currents for the oranges and the yellows. While specific LEDs will differ in light output, an average 5mm orange high brightness LED would give 4200 mcd luminous intensity vs 5800 mcd for the yellow, both at 20 mA forward current.

Edited:
The frequency of a basic symmetric multivibrator (both base resistors are equal, both capacitors are equal) is given here:

https://en.wikipedia.org/wiki/Multivibrator

and is 0.72 /(RC) Hz where R is the base Resistor (1k in your case) and C is the capacitor (10uF in your case). This gives the oscillation frequency of 72 Hz. This is much faster than the eye can detect, in other words, the LEDs connected to the multivibrators will appear to be continuously lit, which makes the multivibrators redundant. Aim for a maximum frequency of ~5 Hz.
 
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Aside:

Since the OP is a newbie. R is sometimes used as a decimal point, so 100R1 is 100.1 ohms. The decimal points tended to get lost in drawings. While we are here, resistors may have 2 or 3 significant figures and a multiplier. So, red-red-red is 2200 and red-red-red-red is 22200 ohms. You can also find resistors labeled like 1002 which means 100 with 2 zeros or 10,000 ohms.

==

Don;t put LED's in parallel. Different color LED's have different forward voltages. LED currents are all over the map, but a ballpark number is about 10 mA for a red LED.

Take into account all of the voltage drops. The led itself and the transistor switch. 0.6 V or so is used as a ballpark number for bipolar transistors.

Data sheets are your friend. For your battery: https://www.google.com/url?sa=t&rct...=VR7pdvAJ9s7Yvqd1AZQCVQ&bvm=bv.68191837,d.cWc

With a 34 mAh capacity and say 10 mA for a LED, it should give you a clue that the battery is not suitable. Further investigation shows that the battery also looks like an ideal voltage source in series with a 1500 ohm resistor.
 
Thanks a lot for your input, altough I don't yet grasp all of it. But, as I understand, aside from the oscillation frequency, I should replace the AG3 batteries with 3 AA batteries, and than it should work, or?
 
Yes, the three AA batteries should work. A typical AA Alkaline battery is rated around 2500 mAh. While that does not mean you will get 2500 mA for an hour it should be enough to power your project. If you plan to parallel LEDs as drawn you will need a series resistor for each LED. That has been mentioned. I suggest a Google of Parallel LEDs and gain an understanding of how a parallel LED circuit works. Also, typically different color LEDs have different forward voltage and current, this is why knowing your LED specifications is important.

Ron
 
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