Mbed negative volt tolerance on ADC pins

02 Jul 2011

Is it like -0.5 500mv for mbed ADC:)

02 Jul 2011

If it is Zero 0 can somebody post me a circuit:) of how I do that.

02 Jul 2011

Don't use a negative supply in your circuit :D that's how.

02 Jul 2011

Igor Martinovski wrote:

Don't use a negative supply in your circuit :D that's how.

It's not true for operational amplifier is always the chance it can swing to the negative side,

This what Gertk posted keeps the signal before the operational amplifier keeps the signal in the + postive side, So do you know circuit that will do this on the output of the operational amplifier. I am trying to protect her, you don't like protecting???

/media/uploads/gertk/micamplifier.jpg

02 Jul 2011

Where does it say that you must use an op-amp with a dual power supply. You can always use an op-amp with a single supply (i.e. no negative rail). You just have to do a little bit of research.

+/- 15V supplies for op-amps make life easier in most cases. In this case, a single supply design is the right choice. If you choose the right op-amp, you can even use the +5Vout for the supply. You will never have to worry about going below (or above) the 0-5V safe operating conditions of the mbed.

Again, if there is no negative supply in your circuit, you do not have to worry about going below 0V. So look for a circuit that works with 0-5V.

You can get started here: http://www.swarthmore.edu/NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html

This doc will probably have everything you need: http://www.nalanda.nitc.ac.in/industry/appnotes/Texas/analog/sloa030.pdf

02 Jul 2011

Igor Martinovski wrote:

Where does it say that you must use an op-amp with a dual power supply. You can always use an op-amp with a single supply (i.e. no negative rail). You just have to do a little bit of research.

+/- 15V supplies for op-amps make life easier in most cases. In this case, a single supply design is the right choice. If you choose the right op-amp, you can even use the +5Vout for the supply. You will never have to worry about going below (or above) the 0-5V safe operating conditions of the mbed.

Again, if there is no negative supply in your circuit, you do not have to worry about going below 0V. So look for a circuit that works with 0-5V.

You can get started here: http://www.swarthmore.edu/NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html

This doc will probably have everything you need: http://www.nalanda.nitc.ac.in/industry/appnotes/Texas/analog/sloa030.pdf

Igor I am designing something where a split power supply op-amp is needed I am giving the user a choice of inputs.. I am going to be using my own circuit with my own design base around the lpc1768..

When using a split power supply op-amp with the lpc1768 how would you keep the the output postive.

And things can go wrong with op-amps with a single supply that can cause it to go negative.

02 Jul 2011

How can a single supply op-amp cause the output voltage to go below 0?

Use dual polarity for your other stuff. But for that op-amp, you can use a single 0-5V supply.

02 Jul 2011

Igor,

Are you trying to say you don't know how to answer the equation:)

Why not just say I don't know how to do it like you haha.

02 Jul 2011

I have no problem limiting my circuits to use 0-3.3V. Every application is different.

You seem to be looking for an easy circuit to solve your problem. You were given one. Then you said it didn't work. I offered a different alternative, and you didn't like it.

You seem to have a copy of The Art of Electronics, that can explain how to do it better than I can :) I am sure it's in there.

02 Jul 2011

Igor Martinovski wrote:

I have no problem limiting my circuits to use 0-3.3V. Every application is different.

You seem to be looking for an easy circuit to solve your problem. You were given one. Then you said it didn't work. I offered a different alternative, and you didn't like it.

You seem to have a copy of The Art of Electronics, that can explain how to do it better than I can :) I am sure it's in there.

no no know know You don't know how to do... and never answer the question I ask.. you give the wrong answer..maybe you should look at my Avatar and see if you can match the dots up:)

02 Jul 2011

I do know how to do it. My choice would be to use a rail-rail op-amp in a single supply operation. You don't seem to like it.

03 Jul 2011

According to the NXP LPC176x datasheet (which is on their web site), the limiting values for analog input voltage is -0.5V to +5.1V.

03 Jul 2011

Formatting went wrong. Try again!

According to the NXP LPC176x datasheet (which is on their web site):

The limiting values for analog input voltage are -0.5V to +5.1V.

03 Jul 2011

Paul Griffith wrote:

According to the NXP LPC176x datasheet (which is on their web site), the limiting values for analog input voltage is -0.5V to +5.1V.

Thanks a lot Paul: I got eye problems is why I missed it :)

/media/uploads/mbed2f/0.5.jpg

03 Jul 2011

Hey I figure out how to keep it positive, cant get much of I sine wave tho:)

Same for the -500mv /media/uploads/mbed2f/positive.jpg /media/uploads/mbed2f/no_sine.jpg

03 Jul 2011

Ha ha...I only give negative feedback lol

03 Jul 2011

Adam Green wrote:

Ha ha...I only give negative feedback lol

mbed, the fastest way to prototype with ARM based microcontrollers.

What does that mean I don't understand.

03 Jul 2011

It wants to be a sine wave /media/uploads/mbed2f/sine.jpg

03 Jul 2011

you can also use the scaled down pictures....

03 Jul 2011

I can't help it My leg covers half of the constellations, I thought it does it automatic anyway, maybe you should write it in assemble language.

03 Jul 2011

Philips Philips wrote:

What does that mean I don't understand.

http://www.zazzle.com/i_only_give_negative_feedback_tshirt-235418768503010114

Philips Philips wrote:

, maybe you should write it in assemble language.

Assembly language is for newbs. Real engineers write in solder.

03 Jul 2011

Adam Green wrote:

Philips Philips wrote:

What does that mean I don't understand.

http://www.zazzle.com/i_only_give_negative_feedback_tshirt-235418768503010114

Philips Philips wrote:

, maybe you should write it in assemble language.

Assembly language is for newbs. Real engineers write in solder.

Look I have some what of a sine wave now how to move it down to the center. Are you trying to say I should use a inverting amp

/media/uploads/mbed2f/_scaled_look.jpg

http://mbed.org/media/uploads/mbed2f/look.jpg

I scaled it down so Gert don't cry

03 Jul 2011
04 Jul 2011
04 Jul 2011

That look strangely similar to a simple op-amp i know...

04 Jul 2011

Excuse me that is a creation by the greatest of the greats of women: hahahha ahha:),