Automatic gain control

You are almost funny. Your namesake was a bit slow, too.

Don

No, but it appears you are.

Don

How do you decide someone is wrong until you know what they are attempting to do?

I don't care what he does with the 5V output, or whether he uses the information that can be obtained from the ADC signal. It has nothing to do with the question; "Is there a way to do it".

You think the OP is stupid, but you show yourself to be narrow mindedly ignorant.

Don

Why?

Don

Download...

Then come back and tell me what "tablets" YOU'RE taking ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

You want to educate yourself about a circuit element called a "comparator". You don't need an "AGC."

Carrier is 60KHz, data is amplitude modulation... 1Hz, variable width.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Yes, download...

to see how it worked.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

The OP is a "bit head" as the requirement for 5V and other ridiculous statements he makes gives away. The application is obviously for a strain detection switch.

Unless, the gain control is very linear and you want 1/V on the output.

BTW: He could change the drive voltage to the bridge to make the scaling equal.

--
--
kensmith@rahul.net   forging knowledge

--
But, YFI, there _are_ no discernible differences in the stain gages
from the POV of the "AGC", all there are is output voltages which
can be the same no matter which strain gage is being used.  Go back
and read the OP\'s request again.  And again.  And again.  Until it
finally sinks in that he\'s asked for something that can\'t be done.
If you think it can, I\'d be extremely interested in seeing a
schematic.

Thanks, I downloaded it and will study it another day (or 3).

Don

--
I\'ve already explained it a couple of times but, unfortunately, it
seems to be so far above your head that you just can\'t get it.

In order to get a better feel for why it\'s impossible, I suggest you
go back and re-read the OP\'s post as many times as necessary to
understand what he wants to do, and then try to come up with a
design and a schematic which will make it happen.

Good luck.

Hello John! I got your point. I thought about that also. What I wanted to do (I don=B4t even know if it=B4s possible) is to create some sort of a "system calibration!" . It would enter a "system calibration mode", input whatever signal(10mV, 20mV) and have a proper gain to get to 5V. Then, with that gain, I would leave the calibration mode and do whatever I want. At this point the automatic gain control would not be on. understand? I have a FIXED gain, when I have a 10mV input, I would get, for exemple, 5V at the output. But if I changed my input (a 20mV input), It would go to 10V and that=B4s not what I want... I had this idea(im sorry if its a stupid idea! :-) ) because I don=B4t want to lose resolution when using an ADC to acquire the signal and also because my ADC accepts only 0-5V input signal. If you (or anybody) have another idea of how to do it without an automatic gain control, it would also be helpful! Thanks a lot for your reply! Victor

With each strain gage have a resistor glued to it. The resistor is picked to give you the gain you want. (The resistor is the feedback resistor on the op-amp.)

Hello Spehro

Maybe I couldn=B4t express myself the best way. But , as my last post says(the one I replied to john), I just want to adjust the gain to get a maximum resolution of my ADC. Maybe I could have some pre-selected inputs(10mV, 20mV, 40mV and 80mV) and have only four diferent gains.... Regards Victor

Spehro Pefhany escreveu:

com

com

...

The OP wrote, "Does anybody have an idea of how to build an automatic gain control (AGC) circuit??? For exemple, amplify a signal (10mV signal or 20mV signal) to 5V. Regardless of what is in the input, the output should be 5V..." which is easy to do with a connection between +5 and Out. In fact, I'd say that the specification, "Regardless of what is in the input, the output should be 5V" practically rules out any other circuit.

-jiw

I know your point! How can the "MAGIC BOX" know its 0,01V(full scale of a 0-10mV) or a 50% of a 0,02V. But I would calibrate it(make it go to full scale) and then have a 5V at the output. For exemple. A 0-10mV input signal with gain=3D500 would give me a 5V at the output. Now, with the same Gain=3D500 I can have a 0-20mV input signal and force it go to full scale(for exemple, compressing my strain gauge all the way so that it goes to full scale), my output would be

10V, right? But isn=B4t there anything that can make this go to 5V and record this proper gain(in this case, 250) to use afterwards? This way, when I enter this "calibration mode" , whatever is the input, the "MAGIC BOX" would know it is the full scale input"! Understand? Maybe it is too hard to implement, maybe not... That=B4s why Im asking you guys because (many of you) are professionals and have a lot of experience. If you say it=B4s something for a doctor thesis, I give up! :-) Regards! Victor

John Fields escreveu:

hehehe im sorry folks! I didn=B4t want that to happen!

Eeyore escreveu:

nd a 10mV

conundrum