Noise on lower end of DAC trace - can I fix this?

[shobley]

In your diagam here:

http://thequark.free.fr/harpe/photos/5.jpg

Can you tell me the frequency of the laser blanking?

And how the circuit is tuned to work with this frequency? I assume it's something to do with the feedback caps on the op-amps...

Thanks.
Steve

[Genesis]

hello
this is the part i need to tune before to give the schematics on the web.
but with theses value the sensor work well with 70-200Hz of blanking. but need to be tested

[shobley]

I managed to get your sensor built and working - thanks for posting the schematic.

Not quite as elegant as yours, but it's a good start!

Steve

[Genesis]

great
and that work fine for your system?

[shobley]

Well....

I can get it to generate an interrupt on the Atmel processor, so it's doing it's job OK - that's as far as I've got

Do you think that an LM324 Quad op-amp would be OK for this circuit?

(I'm using a TL082 x2 at the moment)

[shobley]

Do you have any information on the photodiode you used?

The only thing I was able to find with a large surface area was the OPT211 chip - everything else was tiny.

[Genesis]

you can use lm324 for this job but the TL084 is better
about the photodiode i not have information. this is a part from barcode laser scanner. but a photodiode with large area can work fine i think.

[shobley]

Photodiode - Can you tell me where you got it from? I'm struggling to find anything like the one in your pictures.

[Genesis]

the one used on my system is from an ebay member who send these surplus part for free.

[shobley]

Mr Genesis,

I was looking at your board assembly and I couldn't help noticing that the two resistors on either side of the photodiode did not make it into the build.

Are you using the PD in a photovoltaic mode?

Steve