Can I remove a cap and issues feeding a sensor with ~5V

I have an Atmega on breadboard, 8MHZ, no Xtal, BOD disabled. Using as a node of MySensors trasmitting to a Gateway.

I have a question and an issue.

This is exactly the breadboard (missing only the NRF, connected direct to the battery and not to the stepup and NRF has the 4.7mF capacitor and works very well on every other node).
Other, the resistor is exactly between VCC and Data (drawed a bit strange on Fritzing, but I can assicure you that resistor 4k7 is between VCC and Data).

This is my sketch > https://pastebin.com/raw/6Kxm238q

The sketch is fully tested and works very well.

  1. Can I remove one of the two 104 capacitors on the Atmega? Or I need both? Atmega feeded directly from battery, I remember.

  2. With this setup, the node doesn't trasmit and if I connect the serial (via FTDI232) Atmega floods it with strange characters and doesn't stop (I did try all the bauds, but default is 115200). The leds on FTDI232 blinks continuosly, 1 blink 1 strange chars printed on monitor serial.

2a) If I remove totally the ground between rails or remove totally the booster (so, for breviti, I don't give anymore power to the DHT22) the node trasmits very well (of course only the voltage) and serial works

2b) If I feed the node with 3.3v (e.g. from the FTDI232) the node transmits and serial is all ok.

At the end, seems that DHT 22 (rated for max 6V) doesn't want the 4.92V OR Atmega crash with this voltage.

How can I discover / find the problem with that 4,92volts ?

Thank you very much.

Please, I'm learning just now to draw the schemas in Eagle / Kicad, so for the moment I can only draw the Fritzing, but I hope that is anyway clear. Thank you.

This is exactly the breadboard (missing only the NRF, connected direct to the battery and not to the stepup and NRF has the 4.7mF capacitor and works very well on every other node).

A new use of the word "exactly" to which I was previously unaware of. I suspect you mean a 4.7uF capacitor not a 4.7mF capacitor.

Can I remove one of the two 104 capacitors on the Atmega? Or I need both?

You need them both. The fact that you are using a battery means it is more important to have them than if you did not. They are required to lower the power source's impedance.

so for the moment I can only draw the Fritzing, but I hope that is anyway clear.

Not very clear at all. You are missing all the wiring of your "node" what ever that is.

If I remove totally the ground between rails .......

Randomly disconnecting grounds is a sure fire way of destroying electronic parts.

Grumpy_Mike, I don’t want flames on forum, but - sorry for bad english, I’m Italian - this is the 2nd post that seems to me that you answer rude to me.

I don’t understand why. I’m a noob in electronic, but I’m asking for a help after homeworks done and not a “dish ready”.

If you “hate me” or “hate my noobish”, it is not important that you answer me. Seems to me that I don’t want anything ready: I want learn where are my errors.

Close the preamble and…

Btw, thank you for the advice of mantain both of capacitors. I need to receck exact value for capacitor on NRF24, probably you are right.

And finally, of course, I don’t remove grounds when all is live and running. If you re-read carefully, I could say “If I isolate totally the DHT 22” or “If I remove all circuits of DHT22 - sensor, wiring and power”. It’s the same.

In your experience, what could be the reason if I feed with 4.92 Atmega floods the serials and with 3.3V no?

2a) If I remove totally the ground between rails or remove totally the booster (so, for breviti, I don't give anymore power to the DHT22) the node trasmits very well (of course only the voltage) and serial works

Perhaps that is a hint.
It's not that the DHT doesn't like 5V, it probably more that your 3V setup doesn't like 5V signals introduced.

this is the 2nd post that seems to me that you answer rude to me.

I am not sure what you think is rude here? It is not my intention, I think you will know when I intend to be rude.

You make statements and I correct them what is rude about that?

sineverba:
for the moment I can only draw the Fritzing, but I hope that is anyway clear. Thank you.

Clear as mud. But that's normal for Fritzing diagrams. No pin numbers/description, lots of unclear connections, missing values... Useless to show a circuit.

How can you even draw Fritzings correctly if you don't have the circuit diagram?

tinman13kup:
Perhaps that is a hint.
It’s not that the DHT doesn’t like 5V, it probably more that your 3V setup doesn’t like 5V signals introduced.

Mmm… are you saying that 5V are … feeding also the Atmega?

Probably I could use a resistor divider voltage to low the voltage to the ~3.3V before input pin? Or better a shift-level voltage 5V<->3.3V ?

Otherwise, I cannot understand how is possible to feed two parts of same circuit with different voltage…

Grumpy_Mike:
I am not sure what you think is rude here? It is not my intention, I think you will know when I intend to be rude.
[…]
You make statements and I correct them what is rude about that?

Grumpy_Mike:
A new use of the word “exactly” to which I was previously unaware of[…]

underlining my mistake for the capacitor. Ok for the mistake, but If me was you I would told “Probably you did write wrong. Usually cap on NRF is 4.7uF. Please check.” Understand that at distance of a screen underlining the errors in that mode seems rude. I think every people was noob at the start of everything…
But it’s ok: I don’t want flame with nobody, expecially with an expert 50k posts users   that could help me (like many other people) to understand my errors.
Have a nice day (and… if want, could be tell me if my idea of use a level shifting is right or… how I can achieve my result)!

The DHT22 can take 5V signals just fine.

If you add 3.3V sensors in a 5V system you generally need level shifters or you may destroy the 3.3V signals with the too high voltage, and anyway things may go wrong in unexpected ways. You also have to be careful keeping the voltages apart.

Without a proper circuit diagram I for one have no idea what you're trying to do, or how it's supposed to be connected, so can't comment on why this would be a problem.

@wvmarle

So, as I did say before, I need a level shifter.

Btw, I’m introducing a 5V sensors feeded in a ~2.74V system.

So this is the issue (main, Atmega flooding the serials and no taking read).

Thank you for point me in right direction!