Question about Electronic Components
Drud0616
Posts: 26
Hello everyone,
I was researching some parts I would like to play with for educational purposes and was wondering if I am better off purchasing parts from parallax or from another distrbutor such as digi-key for my projects involving a BS2 stamp.· It seems as though the prices are better from outside distributors for many parts·so I would be saving a lot of money in that regard, but I am not sure if many of the parts that are sold here in the Parallax·Component Shop· are specially made for their microcontrollers.· Basically I would rather stay with a part that will definitely work with my BS2, but if I can save money in the process I would like that aswell.
Some·more questions regarding Parallax Parts...
-What is the difference between a Tact switch and a PushButton?
-Is the Digital Switch DS2405 simply a switching transistor?
-Is an Infrared Transistor the same as an IR Transmitter w/ heat shrink tubing·(without the heatsink tubing)? If so why choose·one·over the other?
I was researching some parts I would like to play with for educational purposes and was wondering if I am better off purchasing parts from parallax or from another distrbutor such as digi-key for my projects involving a BS2 stamp.· It seems as though the prices are better from outside distributors for many parts·so I would be saving a lot of money in that regard, but I am not sure if many of the parts that are sold here in the Parallax·Component Shop· are specially made for their microcontrollers.· Basically I would rather stay with a part that will definitely work with my BS2, but if I can save money in the process I would like that aswell.
Some·more questions regarding Parallax Parts...
-What is the difference between a Tact switch and a PushButton?
-Is the Digital Switch DS2405 simply a switching transistor?
-Is an Infrared Transistor the same as an IR Transmitter w/ heat shrink tubing·(without the heatsink tubing)? If so why choose·one·over the other?
Comments
In regards to your specific questions.
1) The tact switch, or tactile switch, has a positive feeling snap to it when it is pushed. I had to ask the same question when I started with their stuff.
2) As Jon frequently says, Google is your friend. Plugging DS2405 into Google yields the following as the first hit:
www.maxim-ic.com/quick_view2.cfm/qv_pk/2906
3) Can't help you on that one.
Jim
The infrared phototransistor is a transistor activated by infrared light, emitted by an infrared LED. The phototransistor does not need a certain frequency of infrared light like the infrared receiver on our web site.·The "heat shrink tubing" on the infrared LED is actually not that at all but it was in the past - now it's a two-part plastic "case" which narrows the LED's angle by covering the sides and separates the two leads at the base to prevent short-circuits. Make the infrared LED high, point it at the phototransistor and it will trigger. See the "Process Control" book for lots of examples of this circuit (I think it had an op-amp in there, too). The plastic·shields around the infrared LED·were molded by Parallax so you won't easily find them elsewhere, but the phototransistor can be purchased for less elsewhere.
To answer the broader question about where to buy these parts, buy them wherever you want. But I can give you some tips.·You can certainly find LEDs, resistors, pushbuttons cheaper at DigiKey or Mouser. Parallax doesn't addmuch "value" to these, but because they are tough to handle we probably charge 2x our cost or much more (but not as much as RadioShack). But often we buy these components from Asia and our costs can be quite low. Good deal? Maybe so, maybe not. It certainly is reasonable if you are already getting some other products from Parallax and you need only a few components of this nature. But don't buy 100 LEDs from us.
These passive components (switches, resistors, LEDs) are also replacements from our educational kits. Any part available in our kits is available individually on our web site. Our books have excruciating detail about some components, such as that tact switch you mentioned. For example, Basic Analog and Digital has drawings from the top, from the side, Corel-drawn schematics, breadboard pictorials, etc. Our purchasing agent knows she can't easily accept supplier-pushed substitutions because our editorial staff would go bezerk (honestly, truly crazy). Therefore you will find very high consistency in the type of part we provide.
Other parts we manufacture with varying processes. For example, our AD592 Temperature probe is encased in epoxy-sealed heat shrink tubing so it can be submersed in water or soil. The Memsic 2125 Accelerometer is available only in SMT (and in high volumes) so we designed a PCB with the necessary resistors. Right now we're designing a small board for a digital compass that's only available in 2,500-unit volumes in SMT format (designed mainly for automobile industry). For these types of parts we add value through engineering, manufacturing, being able to purchase the minimum quantity and [noparse][[/noparse]most importantly to our customers] we document them completely with our BASIC Stamp. So, they cost more because we add much more to the original IC or sensor.
And our sales of the manufactured sensors mentioned above show that our approach is reasonable and fair for our customers, so I suggest you buy them from Parallax unless can find the exact same part for less (count shipping too) from another supplier.
To answer the question about compatibility, you can use any Component Shop parts with any microcontroller (usually) but our documentation only covers our own microcontrollers. This year you will see many more sensors added to our Component Shop, as well as a reorganization and improvement to the presentation.
Ken Gracey
Parallax, Inc.
Post Edited (Ken Gracey (Parallax)) : 3/17/2005 6:01:01 AM GMT
Yes, you can buy cheaper from Digikey -- but there's a few components where size and fit are critically important, like the snap-switch, or a 5.1/2.2 mm power barrel connector to be soldered to a board. And there are some parts that are not available in the onesy-twosy quantities I need for prototyping.
As a result, you can spend LOTS of dollars buying parts from Digikey that almost, but not quite, fit the board you have. Thus they are basically useless for you. Too small, too big, surface mount only, different current requirements, etc. For another instance, the 50 Mhz resonator for the SX28 chip is really hard to find in individual lots. So is the little can crystal needed for the DS1302. It is also awfully nice to buy a kit of parts you KNOW is complete, especially for that first learning prototype.
Thus Parallax is providing a very valuable service making all these things available, and that is what you are paying for. The part, PLUS all the effort Parallax has done to find just the RIGHT part, and make sure their suppliers keep supplying just the RIGHT part. For completely generic components like LED's, resistors, capacitors, TIP120's, even darlington arrays, go to Digikey. But for those critical components like resonators, power connectors, snap-switches, Parallax really is cost effective.
Now, for educational purposes, where you are going to be buying 20 to 40 'sets' of things, you could buy the first prototype from Parallax, then take those part numbers to Digikey for the next 19 sets.· There are no components "engineered" just for Parallax.· Parallax does create their own unique mounting boards for special sensors, and there are a few vendors that make special boards for Parallax.
Conclusion:· Once you know exactly what components you need (the first prototype from Parallax) find which ones are 'generic' and available from Digikey.· Buy them there.· For the non-'generic' components, you'll probably HAVE to get those from Parallax.
Post Edited (allanlane5) : 3/17/2005 2:24:13 PM GMT
How would I go about connecting the IR Transistor to the BS2 and program it? The IR Reciever seems like it would be easier to set up since it is documented in IRremoteBoeBot.pdf
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Sid Weaver
NEW! 4 MB EEPROM
http://hometown.aol.com/newzed/page4.html
·
The engineers on this forum can clarify, but think of it like this:
(a) The phototransistor is activated by the presence of infrared light. It behaves like a switch in this regard, similar to a reed switch/hall effect switch with a magnet. One common application includes cycle counting as an interrupter (IR LED on one side of a fan, for example, with the phototransistor on the other allowing the blades to interrupt the transmission of infrared). Another application that we use (in the Process Control text) is to point both the phototransistor and infrared LED at a fan which is covered with alternating black/white sticky-backed paper. This required an op-amp but it let us count the RPM of the fan.
(b) The infrared receiver is modulated at 38 KHz. It responds only to the same frequency of infrared light. On the Boe-Bot, the BASIC Stamp generates a short burst at this frequency using the FREQOUT command. If the light reflects from an object the receiver pin goes low. While this is useful, the real value of the infrared receiver is that it can be used for communication, decoding of handheld infrared remote controls, etc. Of course, the book you identified shows many applications and covers this in detail.
Ken Gracey
Parallax, Inc.
An IR photo-transistor is a passive device. As "Goldbook" puts it: "A bipolar transistor with its base-collector junction acting as a photodiode, which, if irradiated, controls the response of the device." The big difference is, if you aimed a remote control at an IR Photo-Transistor, you would see the 38 Khz 'blinks', and you'd have to do something about them. An IR-Reciever only shows you the 'envelope' of the blinks, which is MUCH easier for a BS2 to deal with. An IR-Receiver will filter out IR signals from the sun, lights, etc. An IR photo-transistor won't.
Also, you'll need to buffer·(like Ken did with an Op-Amp) the output of the photo-transistor, as it is not an inherently active device (one with its own drivers).
Any advice on a good book I can pick up? For a newbie of course
Also can I use a DB9M to DB9F·Null Modem Cable to connect my pc to BS2?
I found a very cheap one here
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=SNC-2&type=store
Post Edited (Drud0616) : 3/17/2005 8:49:42 PM GMT
http://www.parallax.com/html_pages/downloads/siccurriculum/documentation_sic_curriculum.asp and you can only learn.
Buy them if you want, but download and print them if you can.
No null modem cables to program BS2s - only straight through. Buy it from us, RadioShack, or any electronics surplus store (that's where you can get them for two bucks).
Ken Gracey