-1

this my first time asking questions to electronic community. So, I hope you ll help me. My question goes like this: i have arduino Due board connected to this schematic enter image description here( https://i.stack.imgur.com/W685e.png ) . i used small program to verify what voltage i can get. when i did the measurement i found that i have on : HIGH 2.5 V ( and that's should be normal ) but on LOW i read 1.6 V . i can't understand why i am having 1.6V??

Eugene Sh.
  • 9,986
  • 2
  • 26
  • 41
Haykel Mhadhbi
  • 5
  • 1
  • 1
    Usually the common-gate converter is used when you want bi-directional level conversion. But your circuit won't allow that (because output isn't tied directly to the drain of Q1). So why not just use the more usual open-drain buffer? – The Photon Jul 20 '17 at 16:20
  • 1
    That looks like an over complicated circuit. Wouldn't [this](http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+50%0Af+528+416+576+416+0+1.5+0.02%0Ag+576+432+576+448+0%0Ar+576+400+576+320+0+10000%0AR+576+320+576+288+0+0+40+5+0+0+0.5%0AL+480+416+448+416+0+1+false+3.3+0%0AM+672+400+720+400+0+2.5%0Aw+480+416+528+416+2%0Aw+576+400+624+400+0%0Aw+624+400+672+400+2%0Ao+5+64+0+4098+5+0.1+0+1%0A) suffice? A simple inverter. Or am I wrong to believe that you're trying to make 3.3V to 5V? It's pretty hard to decipher your "truth table" in the text. Im an awful detective – Harry Svensson Jul 20 '17 at 16:54
  • 1
    Possible duplicate of [Logic level converter using Transistors](https://electronics.stackexchange.com/questions/296879/logic-level-converter-using-transistors) – Harry Svensson Jul 20 '17 at 16:59
  • @ThePhoton: open drain buffer? – Haykel Mhadhbi Jul 20 '17 at 18:20

1 Answers1

1

Since you're only doing level conversion one way, try something simpler:

schematic

simulate this circuit – Schematic created using CircuitLab

You do have to program your arduino to output a '1' when you want a '0' on the 2.5-V side and vice versa, but that is normally not difficult to do.

You could also use a 1-gate logic chip such as 74LVC1G07 to get non-inverting behavior and more guarantees about the circuit performance, at a slightly higher cost than the discrete transistor version.

The Photon
  • 126,425
  • 3
  • 159
  • 304
  • Ahh I understand now but just a simple question. What if the power supply isn't 2.5 what if I use 3.3 v – Haykel Mhadhbi Jul 20 '17 at 19:27
  • If you want 2.5 V out, but only have a higher-voltage supply available, you could make a resistor divider that's thevenin equivalent to 2.5 V w 10 kohms (or whatever value you want). For example, 3.3 V with a resistor divider of 41.3k and 13.2k. – The Photon Jul 20 '17 at 20:12