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Help building a o-5v input +5v to -5v output circuit

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fxmech

New Member
Hi I am trying to drive a galvonometer that takes +/-5v input signal.
I was told it could be done using a DAC chip output to an opamp chip.
The Opamp I was recomended to use is a TL082CN which is a dual JFET chip.
I think I have the DAC part of the circuit down, but I need help taking the DAC output and running it through the OPAMP
Could someone help me figure out how to do this?

It sounds like a very simple circuit and maybe my problem is simply that I don't know the correct name to google.
Any help would be very appreciated...
 
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Grossel

Well-Known Member
Not sure I understand you right - You want a linear voltage amplifier that har the following input/output:

Input=0V --> Output=+5V
Input=5V --> Output=-5V

It that is rigth, you'll need an inverting amplifier circuit that has a gain of -2. Also, the positive input terminal should have -1,667V input.
 

fxmech

New Member
Hi I just posted this but it did not go through...sorry if this ends up being a duplicate post
What I need is for the 0-5v output of the dac to go into the galvo unit which has a 3 pin input (+, g, -)
I think the 0-5v needs to be converted into a seperate 0 to 5v and -5 to 0v outputs.

I think the dual opamp is used by doubling the voltage (0 to 10v) shifting it to -5v to 5v then one opamp is used to cutt off the upper half of the signal giving me -5 to 0v out and the second OPamp does the opposite giving me the 0v to 5v part of the signal.... I am new to electronics so its just a guess and even if Im right, I have no idea how to accomplish this...

the output of the dac is a constantly changing signal that will control the mirror position of the galvonometer...
 
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Reloadron

Well-Known Member
Most Helpful Member
You have a galvanometer that is -5 volts to +5 volts with a 0 volts center scale. A normal mirror backed galvanometer. Metering systems like this are generally driven by what is called a null detector circuit. Now what exactly are you trying to do? Step by step what is the objective? What DAC are you using and what is driving the DAC?

Ron
 

panic mode

Well-Known Member
test this
 

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panic mode

Well-Known Member
Explanation:

Above circuit shifts input voltage by 2.5 volt so 0..5V apears as -2.5..+2.5V (hence needs 2.5V reference created by R1 and 2.5V precision voltage reference). then this is amplified to get -5..+5V output. All work is done by first opamp. second one is just buffer. note that you need dual power supply for this to work (+12V/-12V for example).
 

fxmech

New Member
I am driving it off of an arduino using SPI output. I was able to get a bit of info on the net for the DAC part of the circuit but not the opamp.
The setup is ARDUINO out ----> DAC -----> OPAMP ----> galvodriver board input so that it will connect to the +5v and -5v input signal pins on the galvo driver board.

Here is a schematic of the DAC circuit:

DAC-1.gif


The DAC is a TLV5618 and the OPAMP is a TL082CN which is a dual JFET chip.

BTW the galvonometer comes with a power supply and a set of driver boards so that part is already set... all I need is to get the signal that it needs as an input.
Here is a link to the unit I bought and the user manual.

https://www.ebay.com/itm/20Kpps-HightSpeed-galvo-scanner-max35Kpps-/250701784619?pt=LH_DefaultDomain_0&hash=item3a5efda62b
 
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