Trying to build a homemade servo amp. Is the AGC needed?

[logsquared]

No current monitor or temp calculator at this point. I may put a thermal switch on the galvo block that limits the input. This would only help for long term temp. as the thermal mass of my galvo mount is huge. I think if i use the motors rated rms value for fusing i should be ok. Do you think leaving it out is an oversight?

-woody

[Angelillolaser]

I´m using a set xy for a time at 30kpps to get hot galvos, I sense a change of 300mv, output op amp IR SENSOR, (probably the hot is sensed for IR SENSOR) I ´m working on temp calculator
if you can make graphics and animation work aceptable, but no work for target mirrors.
tunning cold set, is different to tunning when it is hot.
I measure 20c for cold ,60c for hot.
Angel

No current monitor or temp calculator at this point. I may put a thermal switch on the galvo block that limits the input. This would only help for long term temp. as the thermal mass of my galvo mount is huge. I think if i use the motors rated rms value for fusing i should be ok. Do you think leaving it out is an oversight?

-woody

[logsquared]

I'm not totally sure what you mean. I thought the cambride temp calculator circuit was for limiting only if the temp reached critical levels. and the current monitor measured the coil current for use by the temp monitor and high freq. damping. If the IR sensors output more due to heating the differential input on the position detector should cancel most of it out. I think if a high degree of accuracy is needed then the AGC circuit should be used to "force" the LED current down from the effect of heat on the IR sensors. In my previous post i said i don't have a current monitor in my design. That is not completely true. I do have a resistor to measurre the motor current and back EMF. however i only use it for damping. Am i making any sense? I could be way off. I am not trained in servo systems.

-woody

I´m using a set xy for a time at 30kpps to get hot galvos, I sense a change of 300mv, output op amp IR SENSOR, (probably the hot is sensed for IR SENSOR) I ´m working on temp calculator
if you can make graphics and animation work aceptable, but no work for target mirrors.
tunning cold set, is different to tunning when it is hot.
I measure 20c for cold ,60c for hot.
Angel

[Angelillolaser]

I ´m trying to remeber servo control using my olds books.


temp calculator is not for critical, when I disconected this loop,
"y" driver,
"Y" projected amplitud increase , while increase temp.



I sense when is hot, amplitude of sensor decrease(boot sensors) and signal position decrease.
similar efect when you decrease the current of the IR emiter.
temperature can´t cancel using diferential amp.
I worked today in this loop, I´ll try tomorrow to fix this problem and write to PL.

how the circuit works?
temp loop, and agc loop
Angel

I'm not totally sure what you mean. I thought the cambride temp calculator circuit was for limiting only if the temp reached critical levels. and the current monitor measured the coil current for use by the temp monitor and high freq. damping. If the IR sensors output more due to heating the differential input on the position detector should cancel most of it out. I think if a high degree of accuracy is needed then the AGC circuit should be used to "force" the LED current down from the effect of heat on the IR sensors. In my previous post i said i don't have a current monitor in my design. That is not completely true. I do have a resistor to measurre the motor current and back EMF. however i only use it for damping. Am i making any sense? I could be way off. I am not trained in servo systems.

-woody

[logsquared]

I sense when is hot, amplitude of sensor decrease(boot sensors) and signal position decrease.
similar efect when you decrease the current of the IR emiter.
temperature can´t cancel using diferential amp.

Ok. i think i understand. You need the Agc circuit to keep the position signal stable. when the IR detectors change with temp (like changing the IR emiter current) it changes your loop gain. An AGC circuit will compensate for the temp changes by adjusting your IR emitter current. I am not sure why the temp calculator is changing your gain. possibly the R/C filter is not correct. I don't think a temp caculator could be accurate enough to correct the temperature changes. therefor, it should be there for protection only.

I have not noticed any major gain changes with my 6230 motors. however i have not run them very long due to the noise problem in my amp.

I was unaware that the position sensors would be that affected by temp. now i am glad i put the agc circuit on my board. when i get the noise figured out i will set the "x" up with AGC and the "y" without. I will report back with the results.

-woody

[Angelillolaser]

You are right, agc control cricuit work to fix gain temp.

(S1-(-S2))*T = Pos position sensor signal

AGC use the factor T(gain ) to fix temp problems.

AGC in complete necesary.


next step: temp calculator, I will conect with and without this loop.
I will report back with the results.
Angel

Ok. i think i understand. You need the Agc circuit to keep the position signal stable. when the IR detectors change with temp (like changing the IR emiter current) it changes your loop gain. An AGC circuit will compensate for the temp changes by adjusting your IR emitter current. I am not sure why the temp calculator is changing your gain. possibly the R/C filter is not correct. I don't think a temp caculator could be accurate enough to correct the temperature changes. therefor, it should be there for protection only.

I have not noticed any major gain changes with my 6230 motors. however i have not run them very long due to the noise problem in my amp.

I was unaware that the position sensors would be that affected by temp. now i am glad i put the agc circuit on my board. when i get the noise figured out i will set the "x" up with AGC and the "y" without. I will report back with the results.

-woody

[drlava]

This all sounds very interesting, do you have a link to the circuit diagram you are working with?

[Angelillolaser]

This all sounds very interesting, do you have a link to the circuit diagram you are working with?

http://www.photonlexicon.com/forums/...&highlight=agc