how to control 5V to -2.5V

Morning All

Looking for some information and circiut example on how to build controllable +5v that will go all the way to -2.5v (or-5v) in linear scale. For example with potentiometer.

does anything like this exist?

Thank you

For a very low current application, something like this could work if you play with the values, otherwise look at inverting charge pumps etc.


So instead of the voltmeter, if i connect that point to PLC would it be true +/- value?


PLC? True?

We are missing a lot of detail.

Are you connecting the voltage to an Arduino or to a different plc.

so i want arduino to output 2.5V/-2.5V through DAC. So i have the MCP4725 and it looks like its doing what i want.

I have hydrulic cylinder that is driven by the depth gauge. its start position is 2,5v than it moves certain distance until 0V, and than waits unti you dial anything btw 0 and -2.5v to select depth. problem with the actual design is that is not design to be smooth. You can have 5 selection of 0.5v increments and the servo valve makes the hyd cylinder jump rather to go smoothly.

is The ic conected to i2c .
The DAC doesn’t output a negative voltage only 0 to supply voltage. Have you got an op amp on the output to make it bipolar?

Suttle0577 See this is where I struggle with it. I have lm315 somewhere. Can I have thought diagram on how this should be connected please? Thanks

Page 31 has a diagram.
All info is in the data sheet for connecting and using the dac.

So I wired as per diagrams attached, and i have 2.7v at the start (potentially becaususe i used 22K resistors instead 20K which i didnt had at the time) and its going down to 0.6v on the positive side and stops. Cannot get inverted value at all.
I used LM358N which i had.

Not sure what i`m i doing wrong guys.
Any advice?

do you have a -5v connected to the op amp.

Well no, i don`t have bipolar supply. This the whole story here is to have +5V supply and 2.5v/-2.5v out.
I have +10v and -15V available on the machine.

ok, another question.

If i got it right, as I`m completely zero knowledge about op-amps.
if i provide +vcc of 10v and -vcc of -10v to the op-amp and if i drive mcp4725 from Arduino 0-4096, than on the output from op-amp i will have full scale -10v/+10v? if so, this would be great. :smiley:

yes you should get +10v to -10v.

Awesome. Thanks

picture of a dual voltage power supply. change the 7909 for a 7905 and use a +5volt supply instead of the 9volt and should work fine.

Regulated dual power supply circuit from single battery source.png