Add functionality to existing project with Attiny85

The circuit diagram you posted is well good written.
I don't think you can write without some knowledge.
You can draw a that schematic, but you couldn't read the simulator circuit.
I only just wondered it.
I even thought I was being teased.

I know a little regards to electronics, but sometimes small details just cuts me right off the grid. I beginning to learn to draw schematics now and i understand basic arduino stuff, but bulding own circuits is new for me.

That said...

You helped me understand, sort of, and i will thank you for that. But i must admit that i still are a little confused regards to why the right transistor not gets any power to gate when switch is on.

I know that power takes the shortest way to earth, but still.... :slight_smile:

Vbe is required to pass current through the base of the transistor (approximately 0.7V).
This is the same for the both transistors.
And the collector-emitter voltage (Vce) of a saturated left transistor drops to about 0.3V (depending on the transistor model).
You need a voltage greater than 0.7V for the base to emitter current flow, but it doesn't flow because it becomes 0.3V with left transistor's Vce.

Furthermore, the emitter of the right transistor is connected in series with the LED.
Vf is also required to pass current through the LED (it depends on the color, but let's set it to about 2V).
In other words, a voltage of 0.7V + 2V is required to pass through the right transistor.
Even no current flows at a 0.3V voltage.

This is an apology.

I realized that you might be confusing MOSFET and BJT.

BJT has Collector / Emitter / Base
MOSFET has Drain / Source / Gate

The two work on different principles and have different correct uses.
This curcuit is use BJT, so there is no gate.

It's a link of the simulator.

Please slowly operate the Vbe slider on the right side of the screen.
The voltage displayed in Vce will be the base voltage of the right transistor in the actual your circuit.
(Simulated transistors are ultra-high performance, and Vce at saturation is very low, but in reality it will be 0.1V to 0.3V maybe.)

Yes, thanks. I understand now :slight_smile: I think.

Here is my board layout so far. Nothing is soldered or connected yet.

Some updates from the project. All components are now soldered and i have begin connecting part together.

Good work. :wink:
I feel and glad that the your project is approaching to completion.

By the way, did you found the LED operation that was the subject of this topic?
In above post #25 you said it didn't work.
I and @koraks say that there is no problem if it is as per the schematics.
And I showed the simulation to you.

Did you use a breadboard or something to complete that?

Thanks :slight_smile:

Now, i have not tried anything when i said it don't worked. I just asumed it regard to the schematic because i don't fully understand it correctly.

No, i have not used any breadboard this time. So i take a little risk here when i hard wire the project :slight_smile:

I'm pretty shure this wil work, and if it is something wrong it must be something with wiring regards to the transistors. But i'm confident :slight_smile:

Always test on a bread board first, especially if you're not sure if you understand what you're doing.

On the other hand, please go ahead and do it the way you imagined; I wouldn't want to keep you away from the valuable experience of having to rework a circuit, overheating pads in the processes making part of your pcb unusable, the loss of time etc. Great fun, all that.

Yes i know. I have reworked a lot of circuits before. I fell i learn more when i make mistakes, because i then have to find out why etc. :slight_smile:

Usually i use breadboard first, but this time not. I think it will work. But i,m not 100% sure. But i will post update here :slight_smile:


I have connected all components noe expect main input and switch. I gave it power in, and it seams to work perfectly :slight_smile:

I'm not finished yet, but it looks good so far :slight_smile:

What kind of semiconductor is going to dissipate all the power to justify that heatsink btw?

This is an old enclosure for an power supply that i just reuse. The heatsink is a part of the enclosure so it's just there for the look :slight_smile:

With all due respect, I feel that this way of thinking is not very desirable.
At least I write the answer with few confidence, and it's a little disappointing for say that it can't be done without trying it.
I think you denying the answer by my own knowledge is a bit wrong. Because you did be asking here because you didn't know for it.
I don't know what other posters think that.
This is my opinion.

Ah I see. Well, don't lose it; it may come in handy one of these days.

I did'nt say that it not worked. I saw that i didnt understand how it worked. At lest that was what i meant.

Btw... i just wan't to think forward and not discuess feelings and what i have done wrong or not earlier in the thread.

I do not want to hurt others feelings in here. So if i have done that i appologise.

I know. But the heatsink is part of the enclosure so it must be there :slight_smile:

One day you will recycle this project and find that the enclosure is actually the very first thing you need :wink:


I actually think you'r right about that :slight_smile: