Hello everyone,

I am an optical Engineer, with a little electrical experience, but it has been a long long time ago since i have made any kind of circuits my self, however that is the "case"here, so i am hoping some one would be willing to assist me.
Normally i would just purchase the component i need, but due to corona, the waiting time for the "dongle" is simply to long, so i ordered the components my self and though i should be able to do this my self - but after two days where i still cant figure out what i have done wrong, i am looking for some help

So the basic concept i am trying to do, is simply generating a signal that i can adjust from an arduino due's DAC pins.
I need to able to adjust it from 0-10V. I have configured the DAC on the due and i have measure the output so i know that is working as it is suppose to.
Now i need an OPAMP circuit such that i get the voltage i need.
Here i found this dongle:
https://www.botshop.co.za/product/lm358-amplifier-module/

I also found the schematic diagram for the dongle:




So i have ordered all the components home, and i have tried to configurate them in the manor of the diagram, but as it is not working - i am pretty sure that i much have done something wrong ^^ btw i have no included the "led" in the beginning of the system. but i am pretty sure it doesnt have an effect so?

So currently i have attached the GND and VCC to a DC power supply, OUT to the oscilloscope and IN are coming from my DAC pin on the arduino.
When i send a signal on the arduino, i see a minor spike on the oscilloscope, which then decreases rather fast again ( i can show image if that would help ?) and in a similar manor when i turn off the DAC signal, i just get a negative signal that goes towards"0" again.

 

Quote from the link you gave....

" Note: this version does not support DC signal amplification "

You must feed the device with AC, not DC levels

Try writing code for a loop - maybe something like:

Set DAC level 1
delay 1 ms
Set DAC level 2
delay 1 ms
jump to start

This should give approximately 500 Hz square wave at DAC output, and amplified output from your amplifier with possibly a little distortion.

 

Yes but when i am "feeding" the IN with the DAC output on the arduino - it should also be getting AC ?

The VCC and GND should still be DC supplied right?

- Since it is supposed to work with arduino, and the common outputs on the arduino are DC

 

Yes but when i am "feeding" the IN with the DAC output on the arduino - it should also be getting AC ?

The VCC and GND should still be DC supplied right?

- Since it is supposed to work with arduino, and the common outputs on the arduino are DC

You need to supply the amplifier with AC and the rails with DC. VCC is DC.

Can I ask what you want this circuit to do? I mean, how will it be applied?

 

You need to supply the amplifier with AC and the rails with DC. VCC is DC.

Can I ask what you want this circuit to do? I mean, how will it be applied?

Okay then i think i am doing that correct - Since the IN which goes to pin "2" on the OPamp are the AC input from the DAC.

Yes ofc - basically i want to do some external signal modulation with one of my optical components and currently this lab doesnt have a frequency genetor, so after trying outwith the amplified signal(but just a digital pin from the arduino), i found that it would work, i just required a higher output( hence the OPAMP ).

I want to send a short pulse to my equipment which then will activate it in the duration of the pulse. But the output of the equipment is equvialent to 0-100% depending on the 0-10V that i supply - so if i want the 100% output i would need to supply it with 10V in the duration etc.

- i dont know if that makes any sense ?

 

The DAC on the Due provides a DC voltage output and the circuit you show will only work for AC signals.

 

The DAC on the Due provides a DC voltage output and the circuit you show will only work for AC signals.

are you sure ? what would be the point of putting a DAC PIN out on the due - if it still just provided DC voltage as the digital PWM pins ?

An example of a different circuit on project hub, they are also using the DAC pin out together with an OPAMP setup
https://create.arduino.cc/projecthub/ArduPic/how-to-modify-analog-output-range-of-arduino-due-6edfb5

 

are you sure ? what would be the point of putting a DAC PIN out on the due - if it still just provided DC voltage as the digital PWM pins ?

A DAC is a Digital to Analog Converter. It takes a digital value and outputs a corresponding DC voltage.

 

Okay then i think i am doing that correct - Since the IN which goes to pin "2" on the OPamp are the AC input from the DAC.

Yes ofc - basically i want to do some external signal modulation with one of my optical components and currently this lab doesnt have a frequency genetor, so after trying outwith the amplified signal(but just a digital pin from the arduino), i found that it would work, i just required a higher output( hence the OPAMP ).

I want to send a short pulse to my equipment which then will activate it in the duration of the pulse. But the output of the equipment is equvialent to 0-100% depending on the 0-10V that i supply - so if i want the 100% output i would need to supply it with 10V in the duration etc.

- i dont know if that makes any sense ?

You want something like this: https://www.amazon.com/KNACRO-Voltage-Module-Converted-Voltage/dp/B07GSTBTBZ

 

A DAC is a Digital to Analog Converter. It takes a digital value and outputs a corresponding DC voltage.

wow okay, i completely missed that - i though it would be AC output.
But okay, then it suddently makes alot of sense that it doesnt work.

I presume its the OPAMP only works with AC current right ?

 

wow okay, i completely missed that - i though it would be AC output.
But okay, then it suddently makes alot of sense that it doesnt work.

I presume its the OPAMP only works with AC current right ?

OPAs do a lot of things, but I linked to a PWM driven module that produces 0-10V above. This is a much better solution. 0-10V control is standard with PLCs and automation and using an amplifier is a dodgy way to get the varying voltages you want.

 

You want something like this: https://www.amazon.com/KNACRO-Voltage-Module-Converted-Voltage/dp/B07GSTBTBZ

hmm i though about something like that, but when i want to suply the 0-10V steady for example 1sec or i wasnt sure it would work with PWM

 

OPAs do a lot of things, but I linked to a PWM driven module that produces 0-10V above. This is a much better solution. 0-10V control is standard with PLCs and automation and using an amplifier is a dodgy way to get the varying voltages you want.

Is it still possible to control the module you sent here with the arduino ? since i want to trigger it in "intervals" / short bursts?

 

hmm i though about something like that, but when i want to suply the 0-10V steady for example 1sec or i wasnt sure it would work with PWM

What is the maximum acceptable stability and slew rate? What is the required precision and how fine does the control have to be?

 

Given the relatively high operating frequency of the PWM input I think the desired voltage would be available very quickly. Only if this was timing critical in very small fractional seconds would I expect a problem for you.

 

What is the maximum acceptable stability and slew rate? What is the required precision and how fine does the control have to be?

hmm in the equipment manual, there arent supplied much information about it - https://www.thorlabs.com/drawings/9...-D98E-2340-AE325E9445D08FC1/KLD101-Manual.pdf
where i want to use the EXT IN.

I want to trigger it in durations of 20ms to maximum 1 sec. So i would say rather fine, and its very important that its "on" in a similar manor each time, else i wouldnt be able to compare my results on the other end.

 

Hi Simon.
This is a simple option.
E

 

hmm in the equipment manual, there arent supplied much information about it - https://www.thorlabs.com/drawings/9...-D98E-2340-AE325E9445D08FC1/KLD101-Manual.pdf
where i want to use the EXT IN.

I want to trigger it in durations of 20ms to maximum 1 sec. So i would say rather fine, and its very important that its "on" in a similar manor each time, else i wouldnt be able to compare my results on the other end.

Given the 1-3KHz input to the module, I don't think 20ms would be a problem at all. As far as repeatability, you'd have to test but I would expect it to be fairly good.

 

Hi Simon.
This is a simple option.
E

Hey eric,

Would that work with the DC input i have from my arduino DAC?
because this looks alot simplier then the initial diagram.

 

Given the 1-3KHz input to the module, I don't think 20ms would be a problem at all. As far as repeatability, you'd have to test but I would expect it to be fairly good.

Okay, i will look into that option then, just have to find a module that are in europe - so i wouldnt have to wait that long for it tho.