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Lights project for a model (Novice level)

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karlli1221

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Hi everyone... I am a new user here and I am not sure where to post this or where else can I get help from. There is something that I want to replicate (Circuit animation) and I have made a PCB design trying to do the same thing as this circuit. PCB.pngCircuit.png Can anyone tell me if this is OK? I am sorry this is too much to ask but any help would be appreciated.
 

On the circuit animation, it looks like there are 5 LEDs on the left side, of which three are white LEDs, and one is green and another is red?
If so, it is good to remove the 100 ohm resistor, and instead have 5 separate resistors, each one in series with each LED, much like the LEDs
on the right side of the simulation. 100 ohms may be too low for the the red and green LEDs (not sure about white ones), but if you know the
current and the Vf of the LEDs (from the datasheet), then it is easy to calculate: R = (Vin-Vf / I), so if Vin is 9V, and Vf is 2v and I is 20mA, then R=
7/0.02 = 350ohms (i.e. use 330 ohms as the closest value). It should be easy to add the resistors on the PCB, looks like there is some room top-right area.
On the circuit board, it looks like the red and green are in series, which is slightly different from the simulator btw.
I'm not familiar with this software, but normally you'd draw the circuit diagram (using say free version of Eagle), and then it would automatically generate a board from it - you'd move the components to the right places, then place tracks or auto-route, and it would tell you if the tracks were incorrect.
 

Yes, 3 whites, 1 green and 1 red. Oh... I thought one 100 ohms was enough but clearly not. I will work on it thank you very much. It would only take me another minute or two to add the resistors. If I have the red and green in series, (which is different from the animation to save room) Should I use something other than 330 ohms for that one?

Thank you very much once again, I will look into the software Eagle. Just another question, do they have the 4017B decade counter? Because I was having trouble in Crocodile Clips in connecting the circuit to the 4017B. It just keeps blowing up. But thanks anyway.

So the PCB is more or less correct for all other things?
 

I'd try about 180 ohms for the red and green in series.

For the other three LEDs, if they are white ones, then you probably need lower than 330 ohms, I just gave an example calculation. You'd need to check the datasheet for the LEDs, to find out the Vf and I values.

I didn't check the rest of the PCB, but if you draw the circuit in most CAD software, you can (almost) trust the PCB will be correct, because it will tell you if the PCB doesn't match the circuit. Eagle and most other CAD software (some is easier to use - eagle has a learning curve, I just tend to
prefer it, but others prefer different ones) will have the 4017, it is a popular device.
When you solder it up, use a socket for the 4017, in case you need to replace it.

Another way to rapidly experiment is to use prototyping boards, like this one: https://en.wikipedia.org/wiki/Breadboard
 

I have checked the datasheet before and I remembered that the Vf and I values are all very close (1.95-2.1V and 20-30mA) but I will check again.

I will try Eagle for now (I just started downloading it). I did think about breadboarding the circuit before hand.. but I really don't have a breadboard and I have had bad experiences with them.

Thank you very much. Is it ok to get back to you if I have trouble using Eagle? Thanks anyways.

---------- Post added at 11:25 ---------- Previous post was at 11:04 ----------

I am really sorry but how on earth do you use Eagle? I am really stuck and I simply couldn't draw a circuit... Can you possibly tell me some basics of this program? Thank you very much
 

It's not the easiest to learn, but give it a few hours. There is a PDF doc from the cadsoft site that is worth spending the time reading, and also some youtube videos (I don't know what they are like). Eagle is fairly popular, so you'll find lots of tutorials, that will explain it way better than I could.
If you spend half a day on trying them out, I think you'll get used to it (at the end of the day, it's just a software application, not too hard - just
need to get used to it).
 

I have spent about 2 hours trying to figure out how to use it and I think I finally managed to complete the left side of the animation. As I was starting the right side the software stopped responding and crashed. So the file is gone now. But there's one thing I noticed, I found myself doing the exact same thing as when I was creating the first PCB I uploaded. So would you reckon the one I uploaded works (if I change a few things according to you)?
 

Oh, that's a shame : ( It's usually reasonably stable.
With your old software, you drew the circuit diagram, right? And the circuit diagram you drew had the LEDs for example in series, correct?
Then the PCB layout was generated from the circuit diagram? If so, then the computer will check that the PCB is ok compared against
the circuit diagram, so you'll be fine.
 

I drew the PCB when trying my best to copy the animation. The circuit diagram is just another view of the PCB in the software where it tries to give a real world view. I am not sure if the PCB does what the animation does so I was going to ask you. Hopefully it is fine. Thanks a lot anyway ;)
 

Ok, it will probably be fine on this simple circuit.
For larger circuits, don't draw a PCB, but rather just draw the circuit.
The software will auto-generate a PCB which matches the circuit. The software will let you put the components in any position,
and it will automatically draw lines between them, and can even auto-route the lines if you desire.
These methods mean that the PCB is virtuall guaranteed to work, because the computer did the hard work.
 

Oh... I thought on Eagle you still have to route them yourself. Is there auto-route in Eagle?
 

There is, but I'm not sure if it is in the free version. I'm giving the PCB a visual inspection, will reply back shortly.
 

Thank you so much!!! By the way, here is an update but the only thing that changed is the addition of resistors to the LEDs.
PCB1.png
 

The 555 needs pin 1 connected (currently it is disconnected on the circuit simulation too, so not your fault). Also, what is TB2 for? Is it for a separate power supply? You can join them together if you like (or if you don't want to change the PCB now, you could just join with wires from TB1 to TB2.
Apart from that, it looks ok to me. (Not a guarantee that it will work, but it looked ok).
 
Oh I see. So where does the pin1 go on the 555? Because I though pin 1 and 5 does not need to be connected. TB2 is just another power supply and I did it exactly the same as the animation. At that time I just thought two batteries might be better, but I will connect them with wires later.
 

This is a snippet from the data sheet, that is the 0v pin if it's used in an oscillator type of configuration. I think pin 5 will need a capacitor too.
555_circuit.jpg
 
Oh of course... I forgot to ground the 555. So if I connect pin 1 to the bottom "ground rail" of the of the PCB, is that everything?
 

I think so, but don't forget a capacitor on pin 5 to ground too.
 

I have tried removing it in the simulator (animation), it still works. That's another problem. According to my past experience (though not very much) pin 5 doesn't need to be connected... but now I am not sure. Should I still put it there?
 

I think you should put it there. If you find you don't need the capacitor, you could remove it later.
The datasheet should explain the reason for it (It's been a while since I used a 555), but I think it should be in place.
 

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