Hi,
I want to use MCP4725 DAC module with Arduino. When I supply DAC with Arduino, it gives voltages I want. But I must supply it with my circuit. My circuit gives 5.095 volts which can be aproximated to 5 V. When I supply DAC with my circuit, it does not work. (I still connect SDA, SCA, GND pins of DAC) What is the problem? I am very apprecite if you help.

 

A schematic would sure be helpful.

 

A schematic would sure be helpful.

I do not remember exact positions of resistors but the values correct. The measured output of the LM317 is shown.

 

When I supply DAC with Arduino

What is that voltage?

 

What is that voltage?

Nearly 5 v. 5.05 or something

 

My guess is that you made a wiring error. Your schematic, hastily drawn, is missing important information, specifically the pin numbers. It is not possible to verify the proper correspondence between the schematic and the prototype without this critical information being readily available. The very least you could do is take a screen snip from the datasheet and paste it on your schematic.

Then transcribe the numbers from the mechanical drawing to your schematic. Your schematic shows two GND connections when there should only be one. I suspect you have grounded A0, but you should label the pin correctly even if you intend to connect it to GND.

Building circuits is not rocket science, but it does require neatness and attention to detail.

 

Do you have grounds connected?

 

Do you have grounds connected?

of course, yes

 

Then show us a proper schematic with all the connections and part pin numbers.
Guessing what is wrong without knowing exactly how the circuit is connected is not something we normally do.

 

Did you remember the pullup resistors on SCL and SDA?

 

Then show us a proper schematic with all the connections and part pin numbers.
Guessing what is wrong without knowing exactly how the circuit is connected is not something we normally do.

That's putting it mildly!

 

Can we assume that your module includes the mentioned pullup resistors? Can we also assume your Arduino is an Arduino UNO Rev 3 board. This would go much better with an actual schematic and sharing exactly what you have. Finally less you posting your code using code tags I have no idea why it isn't working. Your code is necessary.

Ron

 

Maybe a small filter, 10uf polarized cap on LM output.
Maybe a 0.1uf on MD power pins.
Also, is the Arduino 5V capable/tolerant on those I/O pins driving SCL/SDA??

 

When you say Arduino is powering MD, what voltage?

 

The MCP requires 0.7xVDD or 0.7x5.0V input high on SCL/SDA, if Arduino is only 3.3V drive then you won't get valid signals into MCP. Why not tweak the voltage divider on the LM to run at 3.3V. The MCP can operate on VDD from 2.7V to 5.5V.