IR comm

DestroyerX

I tried hooking up the IR Leds and receivers as shown in the "Robotics With the BOE Bot, Student Guide" but I couldn't get my IR receivers to see anything.

I substituted the 1k ohm resistors with 10k ohm ones. Should it still work?

Thanks,

Jason

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Unreal tournament 2004 rox

Chris Savage

Jason,

·· If you use 10K resistors in place of the 1K resistors, the IR LEDs will not get enough current to even light up.· So, you need to go back to the 1K resistors.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

DestroyerX

Oh, ok, I guess I'll have to use 1K ohm.

When I sorted though my BOE bot kit, I could only find 10K ohm and 22K ohm resistors. Does the serial version of the BOE bot contain 1K resistors? Do they look similar to 200K ohm or 10K ohm (I might have confused them)?

Thanks,

Jason

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Unreal tournament 2004 rox

Chris Savage

Jason,

·· It should tell you this in the manual, but the 1K resistors are BROWN/BLACK/RED for the color bands.· Check again to see if they're in there somewhere, or maybe you used those in place of something else?·

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Jonb

Hook up regular LED to the output pin of the IR receiver with a 220ohm resistor to ground(or none if its too dim), it will give you an immediate visual feedback without going through the stamp.

To figure out which resistor is which:

http://samengstrom.com/elec/resistor/


Note: I like using a FET·to control IRLEDs.·The added isolation from the·microcontroller·also allows·you to pulse the IRLEDs at higher currents. ·In my case I am pulsing them at 40ma. By driving them at higher currents(Some people pulse them at very high amperage, amps even,·to get good range) you get better range at the expense of more power consumption. To compensate for higher power usage, they must be modulated to 38khz but pulsed for shorter periods, or in alternating fashion. You can get away with smaller resistors, but the stamp wont handle the load and could possibly get damaged. There are many ways to do it and a quick search of the last week will reveal many circuits for IRLEDs. I know this may be a bit off topic but its important.·
From the Basic Stamp FAQ:

[b]How much current can the I/O pins handle?[/b] 
On the BASIC Stamp I and BASIC Stamp II, each I/O pin is capable of sourcing 20 mA and sinking 25 mA. The total across all I/O pins should not exceed 40 mA source or 50 mA sink at any given time, however. One exception to this rule exists with the BS2-IC. If the BS2-IC is powered by an external 5-volt regulator capable of delivering at least 100 mA, the total across each group of 8 I/O pins (0 - 7 and 8 - 15) can reach 40 mA source or 50 mA sink providing a total of 80 mA source or 100 mA sink overall. The BASIC Stamp IIsx’s I/O pins can source and sink 30 mA, and the total across all I/O pins should not exceed 150 mA. exception to this rule exists with the BS2-IC. If the BS2-IC is powered by an external 5-volt regulator capable of delivering at least 100 mA, the total across each group of 8 I/O pins (0 - 7 and 8 - 15) can reach 40 mA source or 50 mA sink providing a total of 80 mA source or 100 mA sink overall. The BASIC Stamp IIsx’s I/O pins can source and sink 30 mA, and the total across all I/O pins should not exceed 150 mA.[/b]

^ Keep this in mind whenever connecting a LED or other load directly to a stamp.

Here are 2 good LED resistor calculators:

http://www.luxeonstar.com/resistor-calculator.php
http://www.rc-cam.com/led_info.htm·(bottom of page)
·


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Post Edited (Jonb) : 4/11/2005 12:04:12 AM GMT