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Topic: +-10V Analog input (Read 19150 times) previous topic - next topic

CrossRoads

The ATMega is only a single ended ADC, with max input of 0 to VCC.
-10 to +10 must scaled down by 4 and then offset by 2.5V to get a 0-5V input.
The diode circuit does not differentiate between -Vin and +Vin (-2V looks like same input as +2V).
Further, the input clamps at +5v when the input gets up towards 5V.
http://datasheets.maxim-ic.com/en/ds/MAX1132-MAX1133.pdf
The MAX1132 on the otherhand can take the full +/-10V signal and give a serial result back via SPI interface with much higher resolution.
If one cares to supply higher analog supply voltages via +5V to +/-12 boost regulators (from pololu.com or similar) or via other sources than other external ADC choices are also possible.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

FrankFlin

I think Richard was right. It is all based on your requirements. But it is nice to have options. For me, cost beats out resolution and linearity.

Using a 555 timer to create a digital signal might also work too. I have a lot of those sitting around. Lots of options out there depending on your needs. Hopefully, I'll learn enough to understand 50% of the stuff you guys talk about.

CrossRoads

What is it you're trying to do FrankFlin? The original poster was trying to interface with a CNC machine. What are you trying to do that needs +/-10V to be read?
If you have a triple supply (+5V, +/-15V for example) then there are lots of options for analog stuff to go with the arduino.
Some inexpensive examples are here
http://www.mpja.com/products.asp?dept=13&main=1
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

apollo21

#33
Nov 13, 2010, 12:02 pm Last Edit: Nov 13, 2010, 12:22 pm by apollo21 Reason: 1
Hi
I apologize for words being childish.
At first it is necessary to classify the arguments in four.
I put it in order only with a resistor and the internal standard voltage without using the outside power supply.
I put it in order with power supply 1 and an amplifier.
I put it in order with power supply 2 and an amplifier.
I exclude the power supply from an argument and exclude the insulation (a photo) from an argument with an A/D converter outside and put it in order from communication.
Which do you hope for?

Reply #5 - 17.10.2010 at 12:09:00
Posts: Make it 4, and is already useless; seem to be argued.
He operates a DC servo motor with "UC3638 chip" and wants to do control and monitoring in "ethernet".
When I am very simple in old days by the present when I have crossed it with an individual part, and the servo amplifier can be connected, I admire.
By the way, what will you want to see in "ethernet?"

CrossRoads

I don't think he intended control over ethernet, just monitoring.
I would think control over ethernet would require sending a command ("move X from here to here"), wait for a response back ("moved X"), or a timeout for a lack of response & then a resend of the command.
Monitoring could be simpler - the site just sends out what it is doing ("moving motor x here to here", "done", "moving motor y here to here", "done", "moving motor z", " failed", "program stopped", or "program complete") then someone remote could go over & see what was going on.
And if a message or 2 didn't survive the ethernet transfer, it is not the end of th world.  The receive side could also check to see if messages stopped coming in & alert the listener "xxx seconds with no response from CNC machine, go check on it".
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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