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Topic: Arduino Due signal amplifier from DAC (Read 518 times) previous topic - next topic

Manewc

I have a arduino Due connected to MCP4922 DAC and I need to boost the signal coming from that output from 0-5V to 0-25V, having looked around is the LM358 module enough to do this, I am using a module due to not having a huge amount of experience with amplifiers.

If not will the LM258 operational amplifier meet those specs (i am open to building the circuit if i have too).

MCP4922 datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/22250A.pdf

LM358 datasheet and module schematic:
http://www.ti.com/lit/ds/symlink/lm358.pdf
http://www.electrodragon.com/w/index.php?title=LM358_module
http://www.electrodragon.com/product/lm358-operational-amplifier-signal-amplifier-module-arduino-supported/

LM258 datasheet:
http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=lm258&fileType=pdf

If none of the above is going to work could you point me in the right direction on what is wrong with them and what i should be looking for.

Thanks a lot!

Manewc

MarkT

The LM358 will work up to 32V supply abs max - so OK at 25V.

That module isn't the thing to get though, since its decoupling capacitor voltage
is not known, it might fail.

Get a DIP LM358 and build the circuit yourself - you need a non-inverting amp
with a gain of +5.

Put 10k resistor between DAC output and +ve opamp input.
Put 10k resistor between -ve opamp input and GND.
Put 40k resistor (1k + 39k) between -ve opamp input and opamp output.
10uF 50+V decoupling cap on 25V opamp supply.
[ I won't respond to messages, use the forum please ]

Manewc

#2
Sep 17, 2014, 05:20 pm Last Edit: Sep 17, 2014, 05:23 pm by Manewc Reason: 1
Looking around even more it looks like i need logic level Mofset,

https://www.sparkfun.com/products/10213 would this work for what i need it do? with a circuit shown below, (there is a motor in the picture, however wont be driving a motor will be going into an ECU)

thanks

manewc


http://forum.arduino.cc/index.php/topic,180297.0.html (first post)


Edit: Just saw the last comment, will LM358 work better than the one linked above, thanks for your help.

MarkT

The DAC produces an analog signal - you need an opamp or other linear amplifier to
deal with that.

That MOSFET circuit is for digital or PWM signals.
[ I won't respond to messages, use the forum please ]

Manewc

Is this the circuit u meant?

If i wanted to use a similar circuit for digital signals coming straight from the arduino is this possible?

Where in the circuit can i put diode just in case to not fry my DACs?

thanks



MarkT

How big a screen do you think I have?!?!

If that's equivalent to this, then yes.


The 10k resistor protects the DAC pin (hopefully), but you could add a schottky between it and the 3.3V rail (cathode to 3.3V).
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Manewc

Is it possible to boost my signal up to 25V using a 12V supply voltage? How do you work out the resistor and capacitor values (so i can give it a go).

Sorry about the picture didnt realise it was so big.

Thanks

manewc

MarkT


Is it possible to boost my signal up to 25V using a 12V supply voltage? How do you work out the resistor and capacitor values (so i can give it a go).

Sorry about the picture didnt realise it was so big.

Thanks

manewc


No, I said this: "The LM358 will work up to 32V supply abs max - so OK at 25V."

You have to supply the amp at 25V, and even then it can't quite get the output up to
the +ve rail, you'll get to 23.5V perhaps.  No way round this, you need the voltage.
[ I won't respond to messages, use the forum please ]

Manewc

Hi,

I am little confused, now i understand the amplifier above (i have to supply 25V and to the amplifier and my signal would go from 5V to 23.5V)

Now as i understand it if u have a signal of 5V and u have external voltage supply of 12-14V being given to the amplifier it can go up to 24V with feedback loop? what kind of amplifier would do this if this is possible?

thanks for clearing this up

manewc

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