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PSoC 4

Anonymous
Not applicable

I'm starting a new project which I think the Analog Coprocessor Kit would be a good kit to use for the initial testing. I'm looking at replacing the detector (datasheet attached) with some standard photodiodes and a PSoC.

   

 

   

I have 2 photodiodes, http://www.excelitas.com/downloads/DTS_vtb1112b13b.pdf and https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/VTP9812FH.pdf

   

I plan on connecting the photodiode to a TIA and following that with an ADC. I haven't worked with one of these sensitive circuits since the dawn of ages so I was hoping to get some helpful kick starting tips to proceed.

   

Thanks,

   

George

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8 Replies
rola_264706
Honored Contributor II

So you want to read light level with the ADC?  What are you going to do with the ADC data?

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Anonymous
Not applicable

Yes, going to read the light level and record it over time which will be used to compare against reference samples

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odissey1
Honored Contributor II
        Watch "Photodiode/Transimpedance Amplifier Design" https://youtu.be/FtdJ4e973bk   
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Anonymous
Not applicable

Great video, thanks for finding it but this makes me feel like trying to just use a PSoC isn't going to do the job? I had read some posts where Dana Knight had provided some help with others using photodiodes. Perhaps she'll find this post and chime in.

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odissey1
Honored Contributor II

Georgeloak, just plug PD into input of TI amplifier to get some response. It is only when you need wide linearity range or extra sensitivity or fast response, then some creativity required. I looked into the datasheets of the PD you selected and fluorescence detector. The PDs  have intermediate capacitance range 150/300pf, so you likely do not need a PD bootstrap circuit or negative bias.    

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Anonymous
Not applicable

Thanks, odissey1, I've got both a 5LP board as well as the new Analog Coprocessor board. I'll start with the Analog board since that already has a light detection program that charts the readings. When you say that I might need a bootstrap circuit are you referring to the R/C on the TIA ro an external circuit?

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odissey1
Honored Contributor II

Georgeloak,

   

No. You dont need bootstrap circuit at this point. Just PD and PSoC TI_Amp should give you a good start. I was referring to this circuit from Linear.  

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Anonymous
Not applicable

Attached is the program used for the Ambient Light Sensing Demo App from the Analog Coprocessors Kit. Plugging the VTB1113BH photodiode into VDD and the unused P3.1 pin (TIA_OUT=P3.0, TIA_IN=P3.1) I'm able to measure a varying voltage on the PD's anode as expected. What I'm not quite clear on is the calculations of the constants used in the program for the eval board's TEMD6200FX01.

   

Any helpful advice would be greatly appreciated.

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