Applied Sensors parts question

Mightor

Hi there,

I recently bought the Boe-Bot and I am now trying to gather the parts for the Applied Sensors book. I am having some trouble finding equivalents for the following parts:
* ZTX1049A (The NPN power transistor from Zetex)
* Photodiode, blue enhanced.

Does the blue enhanced mean that is for UV? Those are not so tough to find (albeit quite pricey). I did find some other photodiodes but I cannot be sure that they would do the trick. Everything else is really standard stuff, resistors, capacitors, etc.

Thanks in advance,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Tracy Allen

You can use any small photodiode, but the scale factors will just be a little different. When I wrote that text, the diode specified was about $1.1 each, but the company that makes them went through a big shakeup and the price is now way up (Digikey PDB-V113, $11.56). If I were writing that chapter again, I'd simply use a green or red LED in reverse, because they make pretty good photodiodes, just not blue enhanced. Blue enhanced just means they have a bit more response to blue wavelengths.

Digikey also has the Zetex ZTX1049A. Those Zetex e-line transistors have a high gain and a construction that makes them especially well suited to switch high currents in a small package. I think you can substitute a common NPN transistor like a 2N2222 or a 2N3904, but those will get hotter, or better, one in a TO220 package. The transistor is in the kit to drive the pump, so it has to supply around 150 milliamps.

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Tracy Allen
www.emesystems.com

Mightor

Thanks a lot for the info! I am sure I will be able to find a good substitute now.

Gr,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

aeronuts2005

Sirs...

Any schematic diagram about the IR sensors or the parts list? I am planning to built my own scribbler since no parts is available here locally (Philippines). I have the BS2OEM (given to me as a b-day gift) and some breadboards and resitors... also can i use an ordinary IR LED both for sensor and emitter?




Thanks and more power


Jay Masbad

Tracy Allen

Jay,

I'm not sure which IR sensors you are referring to. Maybe the Scribbler or the BOEBOT?

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Tracy Allen
www.emesystems.com

Mightor

I would like that info as well. I am planning to build my own IR sensor housing and I will most likely mangle a few of them before I get it right. Also after buying a whole bunch of extra sensors (PING)) + servo, compass, inclinometer and digital encoders) for my recently purchased Boe-Bot I've been put on a bit of a budget by the treasury department (read: my wife). Thus I need my electronic parts cheaper than my country's only Parallax supplier sells them for (they've got quite the little monopoly going here).

Tracy, I am specifically looking for the emitter + sensor used in the Boe-Bot.

Gr,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Tracy Allen

The photo receiver is a Panasonic PNA4601M. which has a peak response at a modulation frequency of 36.7khz. It is pretty important to get that exact part, because some of the detetion schemes for the BOEBOT use clever side effects of the response. The IR LED is a Fairchild QEC113. You could use any IR LED, but better results will come from one with higher efficiency, and you will have to improvise your own light sheild. You can find these part numbers yourself by looking at the data sheets attached to the part numbers on the Parallax web site.

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Tracy Allen
www.emesystems.com

Andy Lindsay (Parallax)

For those of you following along, the Scribbler schematic (sans IR Part numbers) and lots more resources are available here:

http://www.parallax.com/html_pages/downloads/software/scribbler.asp

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Andy Lindsay

Education Department
Parallax, Inc.

Mightor

Hi there,

I've been searching Google to find an equivalent for the PNA4601M as none of the big suppliers here in the Netherlands sell it, one of these is a European-wide one (www.farnell.com) and they have a brazillion components (their paperback catalogue is well over 5000 pages and weighs a tonne).
I found the TSOP1837 (http://users.pandora.be/davshomepage/datasheets/tsop1836.pdf). Would this component be a good example of an equivalent component for the PNA4601M? The 1837 variety which has the 36.7KHz carrier frequency is not available from any of the suppliers here in the Netherlands. Only the 33, 36Khz and 38Khz versions. How would I go about calculating the new FREQOUT values for these components? I am not looking for pre-chewed answers, I am actually very keen to learn how one would go about figuring that out. Page 240 of http://www.parallax.com/dl/docs/books/edu/Roboticsv2_2.pdf doesn't go as in-depth as would be required to be able to calculate this kind of stuff (or I am just not getting it). Are the FREQOUT values on page 271 for the frequency sweep somewhat arbitrary values or were they established in some other way?

Thanks,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Andy Lindsay (Parallax)

Mightor said...
Page 240 of http://www.parallax.com/dl/docs/books/edu/Roboticsv2_2.pdf doesn't go as in-depth as would be required to be able to calculate this kind of stuff (or I am just not getting it). Are the FREQOUT values on page 271 for the frequency sweep somewhat arbitrary values or were they established in some other way?

Mightor,

We use the PNA4602M (or equivalent) IR receiver with the Boe-Bot robot, and its center frequency is 38.0 kHz. I had always assumed the Scribbler used the same receiver, but I haven't taken one apart to check. Here’s a link to the PNA4602M. This page will also have links to the datasheet.

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=183020&Row=936204&Site=US

In NL, check with Antratek.

http://www.antratek.nl/

Before going into how to determine the frequencies for distance detection with a different receiver, I'd like to recommend a MUCH better circuit and algorithm:

Better Boe-Bot IR Distance Measurements (Circuit + Programs)
http://forums.parallax.com/forums/default.aspx?f=6&m=99734

Instead of using the IR receiver's response to frequency, it uses different parallel resistor combinations in series with the IR LED to control the brightenss of the IR LEDs, which in turn controls the distance at which the IR detectors will detect an object. Instead of just detecting distance in the 12 to 17 cm range, the parallel resistor approach gets a detection range that more closely resembles the zone diagram on page 271.

Although it's a lot of work, I really hope we'll be revising Robotics with the Boe-Bot soon so that I can replace the existing frequency response distance detection with the material in the Better Boe-Bot IR Distance Measurement thread.

In answer to your question, the frequencies were experimentally determined as described in Appendix G, page 329. Based on the filter curve on page 270 (and the last paragraph on page 269), one “should” be able to just pick a frequency further from the IR receiver’s center frequency and expect the receiver to be more nearsighted. If you used a simple square or sine wave, that is actually the case. However, the BASIC Stamp digitally synthesizes sine waves with duty modulation (a rapid succession of high/low signals that when passed through a filter will shape a sign wave). So, there’s a lot more going on with the signal strength the IR LED transmits than there would be with just a normal square or sine wave. For example, the signal strength (of the sine wave at a given frequency) can change by 10% or even 15% when you change the FREQOUT command’s FREQ1 argument by as little as 10 or 20 Hz. So the IR receiver’s nearsightedness is a function of both frequency and signal strength. With this in mind, I used Appendix G to experimentally find frequencies with similar signal strengths so that they demonstrated the IR receiver’s filter curve.

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Andy Lindsay

Education Department
Parallax, Inc.

Mightor

Andy,

Thanks for your answer. I know about Antratek, I bought my Boe-Bot and all my sensors there. However they have quite a high markup, compared to US prices and charge a very high shipping and handling fee (18 euro). That would make 4 IR sensors and transmitters quite an expensive addition to my bot. They're the only reseller in the Netherlands so there is no competition for them like there is in the US.

As for using a different algorithm, I had already used the project you linked and loved it! I stumbled across it about 2 weeks ago, I believe. It taught me a nice new feature; the input masking. It's what I intended to use together with the IR transmitter I mentioned in my earlier post (TSOP1838). If 38KHz works well then I will just get one of those from my local electronics store. I have no problem supporting Parallax by buying their products such as the bot, Ping)), compass, digitial encoders, inclinometer (I bought all those in the space of about 3 weeks) but for 2-3 euro part I really can't be paying 6-7 times that in postage. I hope you understand. I think my wife would have my hide as well if I suggested buying much more, haha. That wouldn't be too good for business continuity, would it? [noparse]:)[/noparse]

Gr,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Andy Lindsay (Parallax)

Ah, okay, I didn't know that. Sorry for not replying about the TSOP1838 sooner. I think I teseted that part a few years back. If I remember correctly, it was more sensitive than the PNA4602M and had really good noise filtering. I had to increase the series resistance on the IR LEDs just to get it back to a desireable level of nearsightedness for the Boe-Bot. Sure, FREQOUT pin, 1, 38000 should work just fine. Get 950 nm wavelenght IR LEDs if you can. It's always better to have the IR parts tuned to each other and then scale back the detection threshold by increasing the resistance in series with the IR LED.

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Andy Lindsay

Education Department
Parallax, Inc.

Mightor

Andy, Tracy

Thanks a lot for all the info and advice! This forum and all the great documentation available was one of the main reasons why I chose the Boe-Bot over others.

Gr,
Xander

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| What the world needs is more geniuses with humility, there are so few of us left.