TSL1401 Linescan Imaging Sensor Daughterboard BS2pe Motherboard

mclparker

I'm a newbie...please be gentle. Sent this question to Parallax and Dave Andreae there said mabe a gentleman by the name Phil Pilgrim might be willing to answer. Frankly, I don't understand this process...but who am I to question. Mabe I just don't understand what Parallax is. Anyway, I throw this out for Mr. Piligrim in hopes he may be generous with his time.

Here is the question I sent to Parallax:

I am putting together an absorption spectrometer design project for my students. The device design will span the range of 400nm to 1100nm.

I plan on using the TSL1401 Linescan Imaging Sensor Daughterboard and the BS2pe Motherboard.

I have some simple (I hope) questions:

1. Do you have mechanical drawings for the Imaging Sensor Daughterboard giving details such as lens and focus assembly dimensions and physical relationship of the lens to the photodiode array?
2. I read somewhere, perhaps the TAOS site, that the lens is coated. If true, can an uncoated lens be obtained?
3. I choose this package because it seems to be painless in terms of programming. However, I would like to make sure my assumptions are correct:
a. Can the software be configured to read out pixel-by-pixel voltages as a function of time?
b. If so, can the software send the individual pixel voltages and the time associated with those voltages to a computer file in pure ASCII format?
c. If so, what Is the maximum file update rate?
4. Is there any obvious reason why my two choices won’t work for the intended application?
5. If they won’t work, do you folks offer a better choice? My principal fear is writing software, so anything to avoid that goes right to the top of my list.

Any help will be sincerley appreciated.

Mike

Phil Pilgrim (PhiPi)

Hi Mike,

I designed the TSL1401-DB (and the MoBo) and have used TSL1401s (or their predecessors) in various projects for nearly 20 years. So I will try to answer your questions.

1. I do not have such a drawing. However, I've attached separate drawings for the lens and lens holder below. A drawing for the TSL1401R-LF can be found in its datasheet. The lens' optical axis lies nominally between pixels 64 and 65 (starting with pixel 1). In reality, this can vary somewhat, depending on how the TSL1401 is mounted on the PCB and upon how well the lens' physical and optical axes coincide.

2. The lens includes an IR-cut filter. Uncoated lenses that will fit the same holder might be obtainable from one of these sources:

• Universe Kogaku
• Marshall Electronics
• Sunex

3a. Yes. There is a built-in function to read out all the pixels after an exposure as 8-bit values from the AVR's analog-to-digital converter. The values are read out in real time from the TSL1401, since the AVR does not have enough RAM to store them all. So they have to be read out and dealt with quickly to prevent "pixel sag" (explained in the TSL1401-DB manual).

3b. For maximum speed, it would be better to send the pixel data to the PC in binary. The PC will have to attach a time stamp to each bulk upload of 128 pixel values. The MoBo cannot do that on its own.

3c. The update rate will vary and depends on the selected exposure time, the transfer speed of data from the AVR (using OWIN), and the baud rate going to the PC.

4. Sensitivity could be an issue in spectrometer applications. Setting Vdd to 3.3V will be better than using 5V. But you will have to experiment to see if you can get the dynamic range that your application needs. Also, the photoresponse of the TSL1401 at 1100nm is virtually nil; at 1000 nm it's 20% of max; at 400nm, 40%.

5. This is the only linear array sensor that Parallax offers.

I hope this helps. If you have any further questions, please post them here.

Thanks,
-Phil

mclparker

Hi Phil,

You answered every question perfectly. Your generous giving of your time is very much appreciated.

Mike