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FrozenGate by Avery

DIY Laser Power Meter

I powered the board using 2x 9v batteries, and connected the sesor head, but I got 8.2v :-/ at (display out / DMM).
I should be getting ~0v right.
 

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TheMonk said:
I powered the board using 2x 9v batteries, and connected the sesor head, but I got 8.2v :-/ at (display out / DMM).
I should be getting ~0v right.

With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input.  If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.
 
Is this how the wiring should be? I am still getting 8.2v. :-/
 

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knimrod said:
With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input. If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.
 
knimrod said:
[quote author=knimrod link=1200112201/240#241 date=1203363313]With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input.  If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.

[/quote]
I got 8.2v at pin 7 and -8.2v at pin 4.
Was the batteries hooked to the board correctly?
 
TheMonk said:
[quote author=knimrod link=1200112201/240#243 date=1203368937][quote author=knimrod link=1200112201/240#241 date=1203363313]With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input.  If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.

[/quote]
I got 8.2v at pin 7 and -8.2v at pin 4.
Was the batteries hooked to the board correctly?[/quote]

That sounds right... Now disconnect the sensor and ground (short) the input. What's the output?
 
Your Gain Pot seems very far to the Right as well...

Did you follow the formulae and set the Pot before installing>>>

I have built 3 circuits..and never had one even close to that far off of center.

BTW that is the exact Trimmer I used.

It made me look closer at your components

I believe the "Green" resistors you have in there are incorrect....Especially R5.

R5 should be color coded Brn-Bla-GRN-Gld

Yours looks Yellow not green....That would be a 100K Ohm resistor where a 1 Meg is required.!!!!
Check all of those Green colored Resistors...the picture you have doesn't contrast very well...but I think that is where your problem lies

Here is a neat place to calculate color codes...http://www.dannyg.com/examples/res2/resistor.htm


Larry
 
knimrod said:
[quote author=TheMonk link=1200112201/240#244 date=1203373541][quote author=knimrod link=1200112201/240#243 date=1203368937][quote author=knimrod link=1200112201/240#241 date=1203363313]With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input.  If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.

[/quote]
I got 8.2v at pin 7 and -8.2v at pin 4.
Was the batteries hooked to the board correctly?[/quote]

That sounds right...  Now disconnect the sensor and ground (short) the input.  What's the output?
[/quote]
The sensor head was not connected when I measured the voltage at pin7 and pin4.
How do I ground (short) the input?
BTW the board behind the sensor head do I need to remove that?
 
LarryQ said:
Your Gain Pot seems very far to the Right as well...

Did you follow the formulae and set the Pot before installing>>>

I have built 3 circuits..and never had one even close to that far off of center.

BTW that is the exact Trimmer I used.

Just a thought...

Larry
My vr1 = 8.3k

R2=100
R3=45.7K
R4=45.9K

100 x 1000 - (45700 + 45900) - 100 = 8300
 
The green resistors were salvaged from the sensor board 5 band resistors.

R1 & R2 =100 ohm Brown+Black+Black+Black+Brwon
R5 = 1 Mega ohm Bronw+Black+Black+Yellow+Brown (it measured 1mega ohm by itself, but on the DIY board it measured 0.3 and 0.5 mega ohm without batteries and I got similar reading while it was on the sensor head board.
R8 = 1k ohm Brown+Black+Black+Brown+Brown.
 
TheMonk said:
[quote author=knimrod link=1200112201/240#245 date=1203375072][quote author=TheMonk link=1200112201/240#244 date=1203373541][quote author=knimrod link=1200112201/240#243 date=1203368937][quote author=knimrod link=1200112201/240#241 date=1203363313]With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input.  If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.

[/quote]
I got 8.2v at pin 7 and -8.2v at pin 4.
Was the batteries hooked to the board correctly?[/quote]

That sounds right...  Now disconnect the sensor and ground (short) the input.  What's the output?
[/quote]
The sensor head was not connected when I measured the voltage at pin7 and pin4.
How do I ground (short) the input?
BTW the board behind the sensor head do I need to remove that?[/quote]

I think your resistors are correct.

If the sensor head is not attached and the input is floating, the amp will definitely not be happy.  To short, just solder a temporary jumper across the input.  The output should be 0V.

The heater control board does not need to be removed.
 
TheMonk said:
The green resistors were salvaged from the sensor board 5 band resistors.

R1 & R2 =100 ohm Brown+Black+Black+Black+Brwon
R5 = 1 Mega ohm   Bronw+Black+Black+Yellow+Brown (it measured 1mega ohm by itself, but on the DIY board it measured 0.3 and 0.5 mega ohm without batteries and I got similar reading while it was on the sensor head board.
R8 = 1k ohm Brown+Black+Black+Brown+Brown.  



AHHHHHHHHHH....Sry..I failed to notice they were 5 band resistors....

I'm just so used to 4 band..I forgot that those things even existed!

See what happens when you spend too many Lunch Hours in Radio Shack?!?!?! :-[


Sry........I just saw something that jumped out at me...

Larry
 
Kenom said:
so ya got another run of the boards for these comin soon?

The third group buy only lacks 3 more PCB commitments.. See the third post in this thread.
 
knimrod said:
[quote author=TheMonk link=1200112201/240#247 date=1203375829][quote author=knimrod link=1200112201/240#245 date=1203375072][quote author=TheMonk link=1200112201/240#244 date=1203373541][quote author=knimrod link=1200112201/240#243 date=1203368937][quote author=knimrod link=1200112201/240#241 date=1203363313]With an output of 8V, the op-amp is saturated.  Are you sure you have the -9V supply hooked up?  With your voltmeter, verify +9V at U1, pin 7, and -9V at U1, pin 4.   Lastly, disconnect the sensor and ground the input.  If the op-amp is still saturated, there's an assembly problem or a defective op-amp I think.

[/quote]
I got 8.2v at pin 7 and -8.2v at pin 4.
Was the batteries hooked to the board correctly?[/quote]

That sounds right...  Now disconnect the sensor and ground (short) the input.  What's the output?
[/quote]
The sensor head was not connected when I measured the voltage at pin7 and pin4.
How do I ground (short) the input?
BTW the board behind the sensor head do I need to remove that?[/quote]

I think your resistors are correct.

If the sensor head is not attached and the input is floating, the amp will definitely not be happy.  To short, just solder a temporary jumper across the input.  The output should be 0V.

The heater control board does not need to be removed.[/quote]
I shorted the input I got 0.56v, then I re-connected the sensor head it started at 6.5v and went up to 8.2v again.
I disconnected the sensor head and shorted the input again, it went back to 8.2v. :-/
 


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