Re: electronics question please help The modulation frequency of the IR diodes must match the sensor
(depending on exact part number, around 38 KHz) within +/- 3 KHz.  As
you move away from the center frequency, detection drops off sharply.
Are you able to confirm the modulation frequency?
One other problem that I ran into with this same circuit (built using a
PIC as the controller), was the LED itself was at a different wavelength
as the sensor.  I did find that the RS superbright IR LED worked, but
some others did not.  Alot of trial and error.

K.L. McKinnon

Bob Kelly wrote:
> 
> Hello all,
> 
> I hope there is a simple answer for this...
> 
> I have attempted to build the circuit that will allow IR object detection
> using the Sharp IR detector module and a pair of "high output" infrared
> LEDs. The circuit I built was the one from "Mobile Robots - Inspiration to
> Completion, 2nd ed."
> 
> The circuit calls for, among other things, a 74HC04 inverter. I obtained all
> the components from my local Radio Shack. The Inverter that I got is
> actually a 74HCT04 and the IR receiver was the same part number specified
> with the exception of a "B" suffix (hopefully to denote vertical mount Vs.
> horizontal mount). I implemented a slightly modified version of code to read
> the sensor that was based heavily on the info given in the book (I timed the
> LED pulse as required).
> 
> Obviously, or I wouldn't be asking questions, the thing doesn't work. The
> LEDs are working (saw 'em through the video camera) and there is power to
> the Detector (yes, I grounded the case). I wired everything painstakingly
> per the diagram but I was wondering if it is necessary to supply steady
> voltage to the inverter (I have not, and the book didn't tell me to.) I did
> ground the inverter however.
> 
> Is the supply of voltage to the 74HCT04 assumed in the diagram or is it
> likely I left something else out? Also, specific pin assignments for
> connection to the inverter were not given so I carefully wired them
> according to the pin out detail on the inverter package pin assignments and
> symbology. Is the 74HCT04 not interchangeable with the 74HC04?
> 
> Are there any other things I should be aware of if trying to implement this
> circuit on a Handy Board?
> 
> I am new at electronics and I thought this might be a nice "get my feet wet"
> starter project. I don't have access to fancy testing equipment so any help
> at all would be greatly appreciated. I apologize if this question is a
> little on the basic side.
> 
> Thanks again,
> 
> Bob K.

