DPRG mailing list archives: [DPRG]Wall-E -> 1GHZ computers laser rangefinding

Wed Jul 23 15:48:07 CDT 2008

My receiver is picking up ambient light.  Are there any ways to filter that
out?  Should I modulate my laser and put a bandpass filter on the receiver
end?

___________________
Ray Xu
rayxu at tx.rr.com
DPRG member
OOPic group member
Seattle Robotics group member
My Blog

-----Original Message-----
From: Dale Wheat [mailto:dale at dalewheat.com] 
Sent: Tuesday, July 15, 2008 12:13 PM
To: ray xu
Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding

Ray,

Bring your LCD to RBNO this evening and I can show you how to solder a
header on it.

Thanks,

Dale Wheat

(972) 486-1317
(877) DALE WHEAT
http://dalewheat.com

ray xu wrote:
> No problem.  Just ordered today; but the package is going to arrive on
> Wednesday (SO CLOSE!!).  Looks like I will need one of my dad's friends to
> solder the diode...
> 
> Also, I decided to use a 650nm laser diode with an 800nm photodiode (650nm
> is 75% sensitivity).  As for the driver, I finally got some information on
> it.  I was stressing out whether or not to build my own or buy one.  I
> decided to do both; building my own as my backup.
> 
> ___________________
> Ray Xu
> rayxu at tx.rr.com
> DPRG member
> OOPic group member
> Seattle Robotics group member
> My Blog
> 
> 
> -----Original Message-----
> From: Dale Wheat [mailto:dale at dalewheat.com] 
> Sent: Monday, July 14, 2008 6:48 PM
> To: ray xu
> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
> 
> Ray,
> 
> Sorry for the delay but I am just now returning from out of town.
> 
> 
> Thanks,
> 
> Dale Wheat
> 
> (972) 486-1317
> (877) DALE WHEAT
> http://dalewheat.com
> 
> 
> ray xu wrote:
>> Sorry if this is the second email I sent you with the same content, but
> I'm
>> planning to order my laser and all that stuff at latest by Monday
morning.
> 
>> My dad and I decided to use a laser diode driver instead of making our
> own.
>> The attachment is what I plan to buy.  Am I missing anything?  (My dad
> gets
>> very ticked off when I forgot to order something and I have to re-order)
>>
>> Just in case you didn't get my last message; I have no Sent box.
>>
>> ___________________
>> Ray Xu
>> rayxu at tx.rr.com
>> DPRG member
>> OOPic group member
>> Seattle Robotics group member
>> My Blog
>>
>>
>> -----Original Message-----
>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>> Sent: Saturday, July 12, 2008 7:14 PM
>> To: ray xu
>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>
>> Ray,
>>
>> That might be possible.  The problem is that it won't come on at all
until
>> it 
>> gets to the threshold current (3-5 mA) and then maxes out at 7 mA.  It
> would
>> be 
>> kind of tricky.  A constant current driver is not much more complex and
>> would 
>> produce more accurate results.
>>
>>
>> Thanks,
>>
>> Dale Wheat
>>
>> (972) 486-1317
>> (877) DALE WHEAT
>> http://dalewheat.com
>>
>>
>> ray xu wrote:
>>> So I cannot just hook it up to the 5V with a resistor in series?
>>>
>>> ___________________
>>> Ray Xu
>>> rayxu at tx.rr.com
>>> DPRG member
>>> OOPic group member
>>> Seattle Robotics group member
>>> My Blog
>>>
>>>
>>> -----Original Message-----
>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>> Sent: Saturday, July 12, 2008 7:02 PM
>>> To: ray xu
>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>
>>> Ray,
>>>
>>> Yes, I would be especially careful when handing this component until it
> is
>>> installed in the circuit.
>>>
>>> Also, you will have to build some sort of driver circuit for this
device.
>>> It 
>>> does not have any sort of power conditioning circuitry of its own.  I
>> could
>>> not 
>>> find any information on the company web site.  Since they are in
>> Carrollton
>>> TX 
>>> it might be easier to just call and ask for an example circuit.  The
main
>>> thing 
>>> that you want to avoid is too much current through the device.  A
> constant
>>> current driver is not especially difficult to build.
>>>
>>> Also, the beam angle of this device is 20 degrees.  You will have to
come
>> up
>>> with some sort of optics to get it focused into a parallel beam.  This
>> will
>>> be 
>>> more difficult because it is infrared and therefore invisible to human
>> eyes.
>>> Thanks,
>>>
>>> Dale Wheat
>>>
>>> (972) 486-1317
>>> (877) DALE WHEAT
>>> http://dalewheat.com
>>>
>>>
>>> ray xu wrote:
>>>> Since I'm going to be using lasers, are there any precautions I should
>>> take
>>>> to avoid damaging a VCSEL laser diode from electric static?  This is
the
>>> one
>>>> I'm planning to use:
>>>>
>
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=365-1145-ND
>>>> .  I read in an electronics book that they are very prone to ESD.  I
> have
>>>> not worked with lasers before.
>>>>
>>>> ___________________
>>>> Ray Xu
>>>> rayxu at tx.rr.com
>>>> DPRG member
>>>> OOPic group member
>>>> Seattle Robotics group member
>>>> My Blog
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>> Sent: Saturday, July 12, 2008 6:27 PM
>>>> To: ray xu
>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>
>>>> Ray,
>>>>
>>>> My wife, Anne, will be attending RBNO on Tuesday with me.  Thank you
for
>>>> your 
>>>> cooperation.  Please bring your mom if she is interested.  She might be
>>> able
>>>> to 
>>>> give us some interesting information, and she might like the robot
club.
>>>> Who knows?
>>>>
>>>> I have some header pins that we can solder to your LCD that will let
you
>>>> plug it 
>>>> in to a breadboard easily.  I am assuming it's got a 1 x 14 or 1 x 16
> pin
>>>> header 
>>>> along one edge.  I have several similar displays here.
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Dale Wheat
>>>>
>>>> (972) 486-1317
>>>> (877) DALE WHEAT
>>>> http://dalewheat.com
>>>>
>>>>
>>>> ray xu wrote:
>>>>> Ok I'll volunteer to be interviewed.  Rarely I have a headache, and I
>> get
>>>>> sick with the common cold like once sometimes twice a year.  It's
>>> probably
>>>>> because my mom is making my wear these "negative ion" clothing (it
>> really
>>>>> works).  Ask my mom more about it.  Maybe my mom can come with us to
>> DPRG
>>>> or
>>>>> her email is lgnhs at tx.rr.com.  Also, I went to tanner electronics with
>> my
>>>>> dad, again, and we bought a 4x20 LCD that has soldering pads on it.
> I'm
>>>>> still not sure if I need it soldered anytime soon, but I will bring it
>>>> with
>>>>> me to DPRG.  I do not have the header pins, but wires I can provide
and
>>>> will
>>>>> be okay.  
>>>>>
>>>>> ___________________
>>>>> Ray Xu
>>>>> rayxu at tx.rr.com
>>>>> DPRG member
>>>>> OOPic group member
>>>>> Seattle Robotics group member
>>>>> My Blog
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>>> Sent: Friday, July 11, 2008 11:13 PM
>>>>> To: ray xu
>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>
>>>>> Ray,
>>>>>
>>>>> Yes, it is getting late and I'm also waorking late on a project.
>>>>>
>>>>> If you are up to it, I would like to ask you a favor.  My wife is in
>>>> nursing
>>>>> school and is required to interview someone that was born here with
>>>> parents
>>>>> that 
>>>>> are from another country.  The general questions will be stuff like,
>>> "when
>>>>> do 
>>>>> you consider yourself sick" and "what do you do for a headache" and
>>> things
>>>>> along 
>>>>> that line.
>>>>>
>>>>> A)  Do you meet the requirements? and B)  Would you be willing to be 
>>>>> interviewed?  It should not take very long and my wife can provide the
>>>> list
>>>>> of 
>>>>> questions ahead of time.  Questions you are not sure of can be
forwared
>>> to
>>>>> your 
>>>>> parents.
>>>>>
>>>>> If it is possible, I would vertainly appreciate it.  If not, I
>>> understand.
>>>>> Thanks,
>>>>>
>>>>> Dale Wheat
>>>>>
>>>>> (972) 486-1317
>>>>> (877) DALE WHEAT
>>>>> http://dalewheat.com
>>>>>
>>>>>
>>>>> ray xu wrote:
>>>>>> Oh oops I meant the 15th...sorry I'm just a little tired right
now...I
>>>>> will
>>>>>> also bring my robot arm again for nick swan.
>>>>>>
>>>>>> ___________________
>>>>>> Ray Xu
>>>>>> rayxu at tx.rr.com
>>>>>> DPRG member
>>>>>> OOPic group member
>>>>>> Seattle Robotics group member
>>>>>> My Blog
>>>>>>
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>>>> Sent: Friday, July 11, 2008 10:52 PM
>>>>>> To: ray xu
>>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>>
>>>>>> Ray,
>>>>>>
>>>>>> So you will not be at the next RBNO (15th)?
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Dale Wheat
>>>>>>
>>>>>> (972) 486-1317
>>>>>> (877) DALE WHEAT
>>>>>> http://dalewheat.com
>>>>>>
>>>>>>
>>>>>> ray xu wrote:
>>>>>>> Now that my SRF04 has arrived, would you mind soldering on some
wires
>>> on
>>>>>> it
>>>>>>> for me?  Thanks.  I will be at 22nd RBNO.
>>>>>>>
>>>>>>> ___________________
>>>>>>> Ray Xu
>>>>>>> rayxu at tx.rr.com
>>>>>>> DPRG member
>>>>>>> OOPic group member
>>>>>>> Seattle Robotics group member
>>>>>>> My Blog
>>>>>>>
>>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>>>>> Sent: Friday, July 11, 2008 1:45 PM
>>>>>>> To: ray xu
>>>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>>>
>>>>>>> Ray,
>>>>>>>
>>>>>>> If you're using an external counter to measure the time of flight,
it
>>>>>>> doesn't 
>>>>>>> matter what you use to control it.  You can use a PC or a
>>>> microcontroller
>>>>>> or
>>>>>>> even just a display with some buttons.  The main thing is what is
>> going
>>>>> to
>>>>>>> be 
>>>>>>> doing the actual time measurement.
>>>>>>>
>>>>>>> If I remember correctly, a PIC running at 20 MHz can only execute
>>>>>>> instructions 
>>>>>>> at 5 MHz.  There may be some faster ones available now;  I have not
>>>>> worked
>>>>>>> with 
>>>>>>> PICs in many years.
>>>>>>>
>>>>>>> The Hammer board from TinCanTools is probably the fastest MCU that
> you
>>>>> can
>>>>>>> put 
>>>>>>> on a breadboard.  I think it runs 100-200 MHz.  I have a couple of
> the
>>>>>>> ATNGW100 
>>>>>>> boards from Atmel that run at 130 MHz but can be overclocked to 200
>>> MHz.
>>>>>>> They 
>>>>>>> are ~$73 from Mouser or Digikey.  They run Linux.
>>>>>>>
>>>>>>> Building a microcontroller circuit from scratch is not an easy thing
>> to
>>>>> do
>>>>>>> to 
>>>>>>> begin with.  The AVRs that many of the DPRG members work with can
run
>>> up
>>>>>> to
>>>>>>> 20 
>>>>>>> MHz and execute 20 million instructions per second.  Philips makes
an
>>>>> ARM7
>>>>>>> line 
>>>>>>> of processors that are faster, running 60 or 70 MHz.  ST makes an
ARM
>>>>>>> Cortex-M3 
>>>>>>> part that runs at 72 MHz.  All of these chips are in the $10 range.
>>>>>>>
>>>>>>> I'd start with getting the emitter and detector circuits working
>>>> reliably
>>>>>>> first 
>>>>>>> and then figure out what is going to be required to measure these
>> teeny
>>>>>> tiny
>>>>>>> time spans.
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Dale Wheat
>>>>>>>
>>>>>>> (972) 486-1317
>>>>>>> (877) DALE WHEAT
>>>>>>> http://dalewheat.com
>>>>>>>
>>>>>>>
>>>>>>> ray xu wrote:
>>>>>>>> Also, everything will be controlled via the serial port.  At the
>> other
>>>>>>> end,
>>>>>>>> there will be a controller (most likely a PIC) that will handle the
>>>>>>>> transmitting, etc.  The pic will be operating at 20mHz, so will the
>>>>> clock
>>>>>>>> speed be a problem?  Are there any other through-hole MCU that are
>>>>> faster
>>>>>>>> and easy to program?
>>>>>>>>
>>>>>>>> ___________________
>>>>>>>> Ray Xu
>>>>>>>> rayxu at tx.rr.com
>>>>>>>> DPRG member
>>>>>>>> OOPic group member
>>>>>>>> Seattle Robotics group member
>>>>>>>> My Blog
>>>>>>>>
>>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>>>>>> Sent: Friday, July 11, 2008 12:39 PM
>>>>>>>> To: ray xu
>>>>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>>>>
>>>>>>>> Ray,
>>>>>>>>
>>>>>>>> I'm unsure about the dark current adjustment.  I would build up a
>>>>> similar
>>>>>>>> circuit and see what it does.
>>>>>>>>
>>>>>>>> You're right about determining the "system delay".  By setting the 
>>>>>>>> time-of-flight to zero you can measure the other delays in the
total
>>>>>>> system.
>>>>>>>> I don't think you're goning to be able to use a x86 type processor
> to
>>>>>>>> measure 
>>>>>>>> the pulse directly.  As has been pointed out earlier, even if the
>>>>>>> processor 
>>>>>>>> cores is running at 1 GHz, the IO will be much, much slower.
>>>>>>>>
>>>>>>>> If you have the meitter and detector circuits built up and tested
by
>>>>>>>> Tuesday, I 
>>>>>>>> will bring my frequency counter and we can see what kind of timing
> we
>>>>> can
>>>>>>>> get.
>>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Dale Wheat
>>>>>>>>
>>>>>>>> (972) 486-1317
>>>>>>>> (877) DALE WHEAT
>>>>>>>> http://dalewheat.com
>>>>>>>>
>>>>>>>>
>>>>>>>> ray xu wrote:
>>>>>>>>> So for this circuit, there is no need to adjust the "dark current"
>>> and
>>>>>>> try
>>>>>>>>> to eliminate the ambient light using the digital potentiometer?
>>> Also,
>>>>>> to
>>>>>>>>> figure out the delay, can I just apply logic HIGH directly to the
>>>> anode
>>>>>>>> (or
>>>>>>>>> via a mosfet) of the photodiode to "simulate" that it has detected
> a
>>>>>>> laser
>>>>>>>>> beam and the pico-ITX can time it to see how long the delay is?  I
>>>>>>> usually
>>>>>>>>> see op-amps more than transistor amplifiers.
>>>>>>>>>
>>>>>>>>> ___________________
>>>>>>>>> Ray Xu
>>>>>>>>> rayxu at tx.rr.com
>>>>>>>>> DPRG member
>>>>>>>>> OOPic group member
>>>>>>>>> Seattle Robotics group member
>>>>>>>>> My Blog
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>>>>>>> Sent: Friday, July 11, 2008 10:32 AM
>>>>>>>>> To: ray xu
>>>>>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>>>>>
>>>>>>>>> Ray,
>>>>>>>>>
>>>>>>>>> He also has this circuit that should work better for your
>>> application:
>>>>>>>>> http://www.discovercircuits.com/DJ-Circuits/20mrvr2.htm
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> Dale Wheat
>>>>>>>>>
>>>>>>>>> (972) 486-1317
>>>>>>>>> (877) DALE WHEAT
>>>>>>>>> http://dalewheat.com
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> ray xu wrote:
>>>>>>>>>> If you have time, could you please look at the schematic of the
>>>>>> receiver
>>>>>>>>>> circuit?  Thanks.  I based part of it from here:
>>>>>>>>>> http://www.discovercircuits.com/DJ-Circuits/2mhzrvr1.htm .  IC2
> and
>>>> Q1
>>>>>>>> are
>>>>>>>>>> part of the "auto-calibrating" system.  SL2 is where the power
> will
>>>> be
>>>>>>>>>> entering.  Thanks.
>>>>>>>>>>
>>>>>>>>>> ___________________
>>>>>>>>>> Ray Xu
>>>>>>>>>> rayxu at tx.rr.com
>>>>>>>>>> DPRG member
>>>>>>>>>> OOPic group member
>>>>>>>>>> Seattle Robotics group member
>>>>>>>>>> My Blog
>>>>>>>>>>
>>>>>>>>>> -----Original Message-----
>>>>>>>>>> From: Dale Wheat [mailto:dale at dalewheat.com] 
>>>>>>>>>> Sent: Thursday, July 10, 2008 7:31 PM
>>>>>>>>>> To: ray xu
>>>>>>>>>> Cc: dprglist at dprg.org
>>>>>>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>>>>>>
>>>>>>>>>> Ray,
>>>>>>>>>>
>>>>>>>>>> The difference between 4.23 mW and 5 mW will only make a very
> small
>>>>>>>>>> difference 
>>>>>>>>>> in the range.  Having a properly matched emitter and detector
pair
>>>>> will
>>>>>>>>> make
>>>>>>>>>> a 
>>>>>>>>>> big improvement in the performance of the circuit.
>>>>>>>>>>
>>>>>>>>>> An analog-to-digital converter would be much, much too slow to
> give
>>>>> any
>>>>>>>>> sort
>>>>>>>>>> of 
>>>>>>>>>> meaningful result in this application.  You will need to build a
>>> very
>>>>>>>> fast
>>>>>>>>>> amplifier that introduces a minimum of delay into the detector
>>>>> circuit.
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>> Dale Wheat
>>>>>>>>>>
>>>>>>>>>> (972) 486-1317
>>>>>>>>>> (877) DALE WHEAT
>>>>>>>>>> http://dalewheat.com
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> ray xu wrote:
>>>>>>>>>>> Hello guys, I have another question.  Since I'm changing the
>>>>>> photodiode
>>>>>>>>>> I'm
>>>>>>>>>>> using o a very fast response one, I will need to use a 650nm
>>>>>>>>>> laser/detector.
>>>>>>>>>>> But the 850nm one only outputs 4.23mW of light and the one I was
>>>>>>>> planning
>>>>>>>>>> to
>>>>>>>>>>> use originally outputs 5mW of light.  Will that affect my range?
>>>>>> Also,
>>>>>>>> I
>>>>>>>>>>> need some help in building the receiver which means using
op-amps
>>>>> (I'm
>>>>>>>>> not
>>>>>>>>>>> very experienced in that area), or could I use a pre-amplifier
>> then
>>>>>> use
>>>>>>>> a
>>>>>>>>>> AD
>>>>>>>>>>> converter?  
>>>>>>>>>>>
>>>>>>>>>>> ______________
>>>>>>>>>>> Ray Xu
>>>>>>>>>>> rayxu at tx.rr.com
>>>>>>>>>>>
>>>>>>>>>>> -----Original Message-----
>>>>>>>>>>> From: dprglist-bounces at dprg.org
> [mailto:dprglist-bounces at dprg.org]
>>>> On
>>>>>>>>>> Behalf
>>>>>>>>>>> Of John Swindle
>>>>>>>>>>> Sent: Wednesday, July 09, 2008 9:46 PM
>>>>>>>>>>> To: dprglist at dprg.org
>>>>>>>>>>> Subject: Re: [DPRG]Wall-E -> 1GHZ computers laser rangefinding
>>>>>>>>>>>
>>>>>>>>>>> Folks:
>>>>>>>>>>>
>>>>>>>>>>> I think we all like the idea of direct time-of-flight
measurement
> 
>>>>>>>>>>> of light because it seems so straightforward and cool, but as
you
> 
>>>>>>>>>>> probably already know, the laser rangefinders do it with the 
>>>>>>>>>>> phase of the light, not the flight time. Indeed, it can be done 
>>>>>>>>>>> with cheap parts at about 25MHz, not 1GHz. When I was playing 
>>>>>>>>>>> around with rangefinder ideas, I found the plans for the
circuit,
> 
>>>>>>>>>>> but I discarded the link. It didn't take much searching.
>>>>>>>>>>>
>>>>>>>>>>> When I was in college, I thought I could directly measure the 
>>>>>>>>>>> speed of light using a strobe, a photodetector, and a fast 
>>>>>>>>>>> digitizing oscilloscope. It is considerably harder than it would

>>>>>>>>>>> seem. I only got a C on that project. Ouch!
>>>>>>>>>>>
>>>>>>>>>>> Back to my passive sonar stuff now.
>>>>>>>>>>>
>>>>>>>>>>> John Swindle
>>>>>>>>>>>
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> DPRGlist mailing list
>>>>>>>>>>> DPRGlist at dprg.org
>>>>>>>>>>> http://list.dprg.org/mailman/listinfo/dprglist
>>>>>>>>>>> No virus found in this incoming message.
>>>>>>>>>>> Checked by AVG - http://www.avg.com 
>>>>>>>>>>> Version: 8.0.138 / Virus Database: 270.4.7/1542 - Release Date:
>>>>>>> 7/9/2008
>>>>>>>>>>> 6:50 AM
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> DPRGlist mailing list
>>>>>>>>>>> DPRGlist at dprg.org
>>>>>>>>>>> http://list.dprg.org/mailman/listinfo/dprglist
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>> ------------------------------------------------------------------------
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
> 
> 